Under current policies, residential batteries increase emissions in most cases

From Ars Technica

Optimizing battery use to minimize emissions is possible, but generally overly expensive.

Megan Geuss – 12/28/2018, 4:59 PM

A Tesla Powerwall 2.

A Tesla Powerwall 2.

Another year, another reason to take the promises of residential home batteries with a grain of salt.

This month, a group of researchers from the University of California San Diego (UCSD) published a paper in Environmental Science and Technology reporting that there are very few cases in which operating a residential home battery reduces overall emissions—assuming that households are economically rational and trying to minimize costs.

Of course, if the battery is only discharged during periods of peak emissions and only charged when fossil fuel use is low, then a household might reduce emissions. But across 16 representative regions, operating a battery this way ended up being costly.

The results are similar to those published in Nature Energy in the beginning of 2017, although that study looked at a narrower region (99 homes in Texas) and modeled different battery software configurations.

The UCSD study looks at representative homes under 16 different utilities across the country. Each utility has its own emissions profile and unique demand requirements (depending on the weather in the region). The study also looked at three different configuration possibilities:

  1. A demand-shifting configuration, where the battery is used to minimize costs when electricity rates vary by time of day;
  2. A solar self-consumption configuration, where the user has solar panels and wants to maximize the amount of energy they get from those panels; and
  3. An energy arbitrage configuration, where the residential battery owner can buy and sell electricity at retail rates depending on what’s cheaper at the moment.
Further Reading

Want to minimize your home’s carbon footprint? Go for solar, forget the battery

All of these configurations are a little futuristic but still representative of shifts that are happening in the electricity industry today. While most people don’t have time-of-use pricing, it’s becoming more common (this author’s household is charged time-of-use pricing) and it will become the mandatory rate structure for many households in California in 2019. While most solar panel owners prefer not to maximize self-consumption because it’s more cost-efficient to sell electricity back to utilities under net metering, utilities have been pushing back on requirements to buy back solar power from residential customers. The energy arbitrage configuration is the most futuristic, and “reflects the vision of advocates of decentralized energy management,” according to the researchers.

Environmental Science and Technology

The researchers found that the only way to reliably decrease emissions using batteries is if utilities incorporate a “Social Cost of Carbon” into their pricing schemes—that is, charging people extra for using electricity during carbon-heavy periods of generation. This helps bring batteries into the emissions-reducing fold. Unfortunately, including a cost for carbon dioxide emissions has proven politically difficult.

Read the full story here

Environmental Science and Technology, 2018. DOI: http://dx.doi.org/10.1021/acs.est.8b03834  (About DOIs).


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R Shearer
January 1, 2019 2:18 pm

Beats burning yak dung, I bet.

January 1, 2019 2:23 pm

The unicorn flatulence will replace current fuels any day now.
The emissions are understated for a couple of other reasons naturally,all those lovely energies used to produce and install said batteries and the massive and toxic emissions when the battery burns.
Followed by the clean up costs.
I do mean when, not if,they burn as the average homeowner has no clue what kind of device they are planting on their property.
The average citizen can not operate a computer UPS ,let alone change the batteries in one..
And then the installers will most likely be fly by night subsidy miners..

Naturally the insurance companies will be all for these installations until they have enough victims to profitably penalize home owners for these “fire hazards”.

It is a beautiful thing as PT Barnum said;”One born every minute”.

January 1, 2019 2:28 pm

Something must be happening. Ars is usually the home of total global warming hysteria and also of wishful thinking about renewables.

The Ars party line seems to be that we are all doomed unless the US does the obvious thing and goes to 100% wind and solar for all electricity generation, something which would be simple to do, just as China is doing it, and its only because of the corrupt fossil fuel lobby’s denialism and ownership of Washington that we don’t just do it right away.

The other Ars mania is that Paris would have saved the world from its impending climate disaster were it not for Trump’s decision to leave it. The US, by leaving, has, according to Ars, given up the lead to the brilliant and insightful Chinese, who are supposed to be leading the world in reducing global warming by installing vast amounts of wind and solar.

Did you say they are increasing their emissions and installing coal powered plants all across the globe?

Well, you are a fossil fuel funded denier and will be banned without more ado.

Its most surprising that the egregious Timmer has permitted this piece to be published. Maybe even more surprising is that Trump does not seem to be to blame for the failure of batteries to reduce emissions. On Ars, just about everything that goes wrong with the world is entirely the fault of Trump. You see, if only we had elected the best qualified candidate ever instead, things would be so much better, not least we would be leading the world in greenery, Goldman Sachs would be happy, and temperatures would be falling. Or stabilizing. Or something, but it would be better.

Surely the battery issue must be Trump’s fault too, in some way?

Or is maybe Conde Nast is finally waking up?

Kevin Balch
Reply to  michel
January 1, 2019 2:51 pm

Isn’t China building a significant fraction of the world’s coal-fired generating capacity?

John F. Hultquist
Reply to  Kevin Balch
January 1, 2019 4:21 pm

” … they are increasing their emissions and installing coal powered plants all across the globe

from just above, middle of Michel’s comment

Reply to  Kevin Balch
January 2, 2019 12:33 am

Isn’t China building a significant fraction of the world’s coal-fired generating capacity?

Yes, indeed. And if you read the comments threads on Ars on climate and emission you will occasionally find some new and naive commenter pointing that out.

The reply will be a series of furious tirades accusing him or her of being a fossil fuel funded denier, and failing to appreciate the [alleged] fact that China is leading the world in tackling global warming. Usually they are said to be doing this by having reached a coal use plateau, or by installing wind and solar.

I know, this makes no sense. They are not on a coal plateau, and installing wind and solar is having no effect on their emissions. But that is what will be said.

It will also be asserted that all the numbers of plants that anyone mentions are in fact formerly in planning, and on hold, and that they will never actually be implemented. Though no evidence is ever cited for this claim.

Exactly how they are leading the world in fighting climate change, while producing and consuming more coal than the rest of the world put together, while raising their emissions, and while building coal generating plants all around the world….?

Well, its Ars, under the heroic leadership of the egregious Timmer. The swamp that was once a serious source of information on science. Stop making sense!

A detached observer watching these discussions is inevitably drawn to the suspicion that most of Ars commenters on climate issues may be Chinese astroturfers. So great is the refusal and indignation at the idea that to reduce global emissions might require the world’s largest emitter to reduce its tonnage.

Its not the only forum in which one is driven to this suspicion.

January 1, 2019 2:31 pm

Is there a significant loss of efficiency in the charging/discharging of a large battery? For example does 100 watts of charging energy yield 100 watts of available energy? My guess is there has to be a substantial loss. Just losing energy by cycling it through a battery seems so inefficient. Doesn’t Tesla promote using solar panels to charge it’s home batteries?

Peter Morris
Reply to  Tommyboy
January 1, 2019 3:35 pm

If other rechargeable batteries are anything to go by, you lose efficiency on both ends, as batteries heat up during charge and discharge.

But I don’t have any experience with these big wall batteries.

kent beuchert
Reply to  Peter Morris
January 1, 2019 3:59 pm

There is a power loss when both charging and discharging- it applies to all li ion batteries, large or small. Charging losses are likely 10%. Discharge losses depend upon how fast the discharge – larger discharges lose more energy (the reason an electric car driver with a lead foot loses driving range). BUT there are other losses – inversion (going from DC current to AC current) and vice versa – inverters (expensive – they usually cost as much as the solar panels, sometimes more) generally extract 5% as loss, but some are better than that, DC to AC likely the same loss levels.

Reply to  kent beuchert
January 2, 2019 4:21 am

It doesn’t apply to Li-ion batteries. It applies to all batteries and is caused by the internal resistance. It is therefore proportional to the square of both the charging and discharging current. It can therefore go as high as 50% with very fast charging and require active cooling of the battery.

AGW is not Science
Reply to  tty
January 2, 2019 8:04 am

” and require active cooling of the battery”

Which requires…MORE ENERGY!


Reply to  Tommyboy
January 1, 2019 4:03 pm

Classic lead plates submerged in acid type of rechargeable batteries (due to internal resistance) when charged by solar loses about 25% of energy to charge.

Doug Huffman
Reply to  Tommyboy
January 1, 2019 4:19 pm

Peukert’s Effect Law

Reply to  Tommyboy
January 1, 2019 6:19 pm

A Tesla powerwall Round trip efficiency is 89% (at the beginning of its life)

Reply to  jeff
January 2, 2019 4:24 am

At what charging/discharging rate? Internal loss is proportional to the square of the current, and therefore no fixed efficiency figure-of-merit exists.

Reply to  Tommyboy
January 1, 2019 11:00 pm

“does 100 watts of charging energy yield 100 watts of available energy? ”

a watt is a unit of power not energy. Pls learn the difference. It’s like the difference between miles and mph.

If you are asking does 100Wh ( energy) in get you 100Wh out, obviously not , as explained by some above. Every process has losses. Cycling the battery ~10% and since you need to convert the PV output down to battery voltage and then step it up to mains AC voltage to use it later, add at a least another 10%.

All included it’s hard to see it being better than 80% efficient.

But then burning gasoline to make car move or burning coal to make electricity is far less efficient than that.

January 1, 2019 2:32 pm

The researchers found that the only way to reliably decrease emissions using batteries is if utilities incorporate a “Social Cost of Carbon” into their pricing schemes—that is, charging people extra for using electricity during carbon-heavy periods of generation.

A typical case of Astral Traveling. Sounds pleasant to the ear.

Dave N
January 1, 2019 2:35 pm

“Current” policies. Unintended pun?

R Shearer
Reply to  Dave N
January 1, 2019 3:35 pm

Surprised there wasn’t more resistance.

Pamela Gray
Reply to  R Shearer
January 1, 2019 3:59 pm

I think the impedance of progress is a good thing, contrary to when I had to deal with that on my electrodes.

David Dibbell
January 1, 2019 2:37 pm

From the article: “Unfortunately, including a cost for carbon dioxide emissions has proven politically difficult.”

Unfortunately? I would feel more fortunate if the concept of the “social cost of carbon” would die. Living in the state of New York, a carbon cost has been imposed through the back door of what is termed the VDER (Value of Distributed Energy Resources) program established by the Public Service Commission. Consumers are paying for this, whether they realize it or not. Look up “VDER NYSERDA” to see how it works. It’s complicated, but essentially there is presently a $0.027 per kwh component of the “value stack” pricing mechanism which is purely an arbitrary environmental benefit amount – in other words, based on the fictitious concept of the social cost of carbon.

Reply to  David Dibbell
January 1, 2019 11:06 pm

per kWh

It doesn't add up...
January 1, 2019 2:47 pm

The comments over at Ars Technica are unbelievable. The moderator grandly announces that renewable energy is solved, the cheapest source, capable of supplying at least 70% of power. The thread spends much time discussing carbon taxation (which of course would be completely unnecessary were the assertions true), and forgets to mention at all that in many jurisdictions more wind and solar are a matter of law, not economics (or future feasibility). Tax and dividend is seen as the way to deal with the fact that the carbon tax is necessary, but a severe blow for the poorer parts of society, without for a moment considering that even with a dividend if a kWh is now $1, it makes it unaffordable to the poor, even with the dividend, and the much more expensive energy will kill jobs.

Meanwhile, few of the commenters appear to have the first idea about battery economics. The notion of round trip loss, and limited lifetime/operating cycles barely occurs. The reality of course is that batteries for grid connected homes are virtue signalling knick-knacks that can only pay off when heavily subsidised. Their use in grids is confined to providing very short term ancillary services – helping to reduce grid flicker in high renewables environments, and stabilise the frequency.

Reply to  It doesn't add up...
January 1, 2019 5:00 pm

It doesn’t add up…

I generally stay away from comment sections on news sites and blog sites– WUWT being about the only exception. You’ve found the reason why: comment sections are often filled with completely uninformed remarks. I guarantee if you could sit down face to face with the average commenter and analyze the practicality, the economics, and the politics of these crazy ideas, they’d quickly admit ignorance. But when you can hide behind a pseudonym and a keyboard on the Internet, you can say anything! Pigs fly!

Curious George
January 1, 2019 2:58 pm

“If the battery is only discharged during periods of peak emissions and only charged when fossil fuel use is low, then a household might reduce emissions.” How do we know when fossil fuel use is low? When emissions peak?This calls for a battery with an IQ much higher than that of UCSD researchers.

Reply to  Curious George
January 1, 2019 3:13 pm

Presumably, residential batteries can be controlled by the utility’s computer.

If you’re going to let the utility control your battery, what’s the point of owning the battery? Doesn’t it make more sense for the utility to own the battery?

Lee L
Reply to  Curious George
January 1, 2019 4:01 pm

That information is available at each generating source and isnt a difficult offering to a real time database on a network.
Remember that ‘smart meters’ are networked as well and can be offered up to the minute information on the sources of the electricity they meter since the sources know what emissions are associated with their operation as they monitor them in real time. So it isnt all that hard to ‘know when fossil fuel use is low’ and to transmit that info to your smart meter. Smart meters usually will support an in house network such as ZigBee which could be used to inform or control the charge controller or other electrics in a smart battery. Smart meters even now allow utilities to offer the service of managing your air conditioning remotely. It isnt a stretch to envision other devices, such as a battery, to be managed on your inhouse device network.

Curious George
Reply to  Lee L
January 1, 2019 5:10 pm

A smart meter meters your consumption, not a generation of twenty suppliers to your grid. Someone would have to average that mixture – usually a fast changing mixture. If you say that it can be done in principle, I agree. If you say that we are there now, I disagree. I wonder if this something worth doing.

Lee L
Reply to  Curious George
January 1, 2019 6:34 pm

A smart meter does monitor your consumption, but it is much more than a monitor of consumption.
The meters are a deeply networked computer usually with embedded hardware that allows support of a home network like ( as I stated ) Zigbee. Further, we are actually ‘there’ insofar as electric utilities are using the smart meters to remotely control air conditioning and are selling that service. Thermostat… Powerwall… what’s the diff?

Zigbee allows sending commands to, say, a smart applieance .. maybe a command like ‘DONT START’ or ‘TURN YOURSELF ON’. Just think of a Powerwall as an appliance and it really isnt a very big leap. Networks let servers monitor twenty power suppliers easily and those suppliers are all monitoring their own status and performance as part of their control systems on a subsecond basis. They only need to make that info available on a network for it to be monitored and passed on to a server to be transmitted to smart applieances vie smart meters in your home.

This is not rocket science at all anymore.

It doesn't add up...
Reply to  Lee L
January 2, 2019 4:16 am

I guess it partly depends how you define what you are consuming. Consider this simplified grid:

Hydro station —-Town A—–Coal station—-Town B—-Wind Farm—-Town C—Solar Park

You can add up all the instantaneous production easily enough to produce a grid wide average. But Town A gets a mix of hydro and coal in reality. Yet if the hydro station is shut for maintenance or low water, Town A will clearly be 100% dependent on coal, because there is no bypass route around Town B allowing a share of wind and solar to reach them. If you live close to a major power station, you will almost certainly get 100% of your power from there while it is operating, because that’s the way the power flows. However, although Town C has no direct connection other than to wind and solar, on a dark windless night it will get the majority of its power from the coal station: it cannot claim to be virtuously fed by the hydro station.

In a real grid, where there are lots of loops, the calculations for power flows get much more complicated. They are done, because the grid operators need to be sure that links do not get overloaded and blow out, and because they need to be sure that they have a plan in place if generation drops from one or more generators to know which ones to instruct to raise their output to compensate, while preventing “fuse blows” on the grid. You could use the solutions to these calculations to estimate the power flow origins for each link, which is a complex calculation of itself, and is not normally done.

January 1, 2019 3:13 pm

“if utilities incorporate a “Social Cost of Carbon” into their pricing schemes—that is, charging people extra for using electricity during carbon-heavy periods of generation. This helps bring batteries into the emissions-reducing fold.”

That conclusion smacks of a ‘modeled result’.

Great article and graphs.
Thanks to CTM, Megan, Latitude!

Happy New Year to everyone!

Bruce Cobb
January 1, 2019 3:27 pm

“Unfortunately, including a cost for carbon dioxide emissions has proven politically difficult.”
That cost is essentially a tax. It’s not like you have a choice. You have to pay it. We saw how popular “carbon taxes” have been in France recently.

Reply to  Bruce Cobb
January 2, 2019 12:36 pm

“Carbon taxes”?
No, they are not taxes on carbon, C.
They are fund seizures based upon beneficial, vegetation growing CO2 emissions.

CO2 is a gas, the trace atmospheric gas that makes life on Earth possible. Carbon is a solid, and carbon-based fuels are solid (coal), liquid (oil) or gaseous (natural gas).

The entire ‘global warming’ canard is NOT about lowering CO2, but about taxation of CO2 emissions. The last thing the Marxists want is for people to lower their “carbon footprint”, they want money that is utterly dependent upon increasing emissions.
The fact that the left wants to allow you to emit as much as you want as long as you’re willing to purchase ‘credits’, says that it’s not about the environment, it’s about the money.

The same is valid for 3rd world countries which want to extract money from industrialized countries which alleviates them making the necessary changes that would enable business creation and the resultant boost in employment that would occur. Not to mention the vast amounts the elitist in each country can scrape off the top.

The Carbon Dioxide Word Game

steve case
January 1, 2019 3:32 pm

Years ago, sometime in the ’90s I toured an off-the-grid house in Door County, WI. It was built by a guy who billed himself as a professional engineer. At that time the house had all fluorescent lighting and a wood stove. High wattage appliances were propane where possible. Other features were unique. The digester toilet looked like a big bowl of cornflakes. The solar panels were on the roof a small shed maybe 200ft², and the shed contained a bank of ordinary lead acid batteries. There was a four cylinder auxiliary generator which I thought was overkill. He said it had never run. His place was pretty close to if not exactly 45°north.

He told us that the cost of his electricity more than the grid, but he wanted to show it could be done.

Reply to  steve case
January 1, 2019 6:58 pm

Basically, the solar panels were for powering the lights and TV if he had one.

steve case
Reply to  MarkW
January 1, 2019 7:59 pm

He could run toasters and hair dryers that sort of thing. Air conditioning? Don’t know if there are any units made with internal combustion engines to run the compressor. Automotive comes to mind. Of course that would defeat the world of the CO2 warriors. Anyway maintenance of the solar panels and batteries required lots of time. That was at least 20 years ago, there have to be some improvements since then.

Reply to  steve case
January 2, 2019 10:03 am

I used to work for the largest power company in Nevada. It is well-understood that solar power can’t supply the kick needed to start household A/C compressors. (Perhaps solar can provide enough power to keep the compressor running, I don’t know.)

Reply to  steve case
January 2, 2019 6:57 am

I have a 3 BR, 2 Ba house in the UP that is 100% off the grid that has a big solar array and a now back-up 15 Kw propane generator. I just replaced my battery bank with Trojan Carbon batteries, the first lead-acid batteries specifically designed for PV applications. After I installed the new batteries this summer my generator ran for four hours the first week. I have a TV (a power hog even though it’s “high efficiency”), fridge, washer, dryer, microwave, toaster, toaster/oven, and a forced draft water heater. My line frequency is more stable than the local power company’s and my power is more reliable. So, it can be done. Oh, the house is at 46N.

Reply to  Yooper
January 2, 2019 7:57 am

Nobody said it couldn’t be done.
The question has always been, is it economical.

Russ Wood
Reply to  MarkW
January 5, 2019 6:04 am

A guy in South Africa (near Knysna, if I remember right) built a house that was completely off the grid. Pumped water, wind turbines, solar cells, and a room full of truck batteries. He reckoned that it cost him about double that a normal house of that size would have cost.

Reply to  Yooper
January 2, 2019 3:23 pm

People had been comfortably living off grid for very long time. There is never a question whether it’s possible, the question is whether it’s competitive with alternative.

For people like live-aboards (as in living on sail boats), those who don’t live anywhere near energy line and others with similar restrictions, there are no alternatives.

Pretty much for everyone else, using public utilities is much, much cheaper and easier.

Sam Capricci
January 1, 2019 3:46 pm

I was looking at these as a means to go off the grid. But I couldn’t get a straight answer if that was doable and how many and how much I’d need to spend.

I figured the solar PVs I have would charge these Tesla power wall(s) during the day and we’d use them at night. But now that I’ve had the PV system and have been watching production drop by 3% over 4 years I’m not sure that going that route wouldn’t end up with a major investment and an unreliable if at all return for the money.

Reply to  Sam Capricci
January 1, 2019 4:15 pm

is that 3% per year or 3% per 4 years?

Sam Capricci
Reply to  Vince
January 1, 2019 7:29 pm

so far 3% for four years. But I’m concerned it will increase. Each year it has been a downward trend.

Farmer Ch E retired
January 1, 2019 4:02 pm


Juan Slayton
January 1, 2019 4:12 pm

While most solar panel owners prefer not to maximize self-consumption because it’s more cost-efficient to sell electricity back to utilities under net metering….

Not sure about this. May be true for some areas, but not here in Azusa. We may pass kwhrs back and forth, but the power that is delivered by Azusa Light and Water is subject to the state energy tax, the local electric users tax, a public benefit charge, and the “power cost adjustment.” It is obviously in my interest to maximize the amount of power that goes directly to my residential load, as that does not go through the grid meters and is not subject to these charges. It is, of course, a perverse incentive to do my heaviest electrical activities during the maximum solar hours, even though this exactly coincides to when the government wants us to turn down everything electrical.

In theory a modest battery buffered grid tie could completely eliminate passing any power back and forth for days at a time, until the weather goes bad. But this will not be economic until battery life is substantially increased.

January 1, 2019 4:43 pm

Isn’t this kind of obvious?

January 1, 2019 4:56 pm

No, this is not a no-brainer. In the Netherlands, Excess PV power is just subtracted from your daily consumption: you just eliminate very kWh delivered to the grid with the one have used. Withot the additional cost of transportation, taxes, incentive for long term storage. You have tax panels, not solar PV.

January 1, 2019 5:03 pm

If I could get a whole house battery backup for a low enough price, I would get one anyways. It would prevent some blackouts, and hold power on until a back up generator can kick in.

Flight Level
January 1, 2019 5:12 pm

Let’s assume a true battery storage capacity of 7 kWh. At the cost of about 7’000$, give or take the installation process. Roughly what a Tesla solution would be.

Unless looking after a dead-weight, it should be used at it’s full capacity at each cycle, i.e. store the maximum of cleanest energy and supply it when the dirty one should take over. Sun being what it is, dictates one deep cycle per day.

Degradation takes a serious toll on Lithium batteries after about 1’000 deep cycles. Till then, the total stored energy output would be at best 1’000 cycles x 7 kWh = 7’000 kWh.

Even less when real world efficiency is taken into account.

Result, 7’000 kWh come at a an added cost of 7’000$ before possibly a serious overhaul.

I don’t feel that comfortable with an added price of 1$ per kWh. Do you ?

Reply to  Flight Level
January 1, 2019 6:26 pm

7kWh is nowhere near enough, that is subsistence level battery storage. The routine annual loss of discharge capacity alone quickly makes that prohibitive.

If you want a modern home that doesn’t cramp your style or impose limits on what you can do and when, in any season of the year, or any weather, for 10 to 15 years, then you need 4 times as much kWh of storage. 28 kWh might do for a young family, plus a large solar hot water system to remove most of the avoidable draw-down, so that air-con or room heaters plus several computers can operate along with everything else. And that’s if you have excellent insulation.

Flight Level
Reply to  WXcycles
January 1, 2019 9:18 pm

Which rises the replacement/recycling costs.

Batteries, due to their limited charge/discharge number of cycles are what they are: -A luxurious rental temporary storage for electricity.

Which is actually good, very good. For those selling them.

Gordon Dressler
January 1, 2019 5:17 pm

Batteries sized to supply an appreciable part of a residential home’s typical average demand (in the US, about 867 kWh per month averaged over a year; see https://www.eia.gov/tools/faqs/faq.php?id=97&t=3 ), will become one of mankind’s biggest wasters of electrical energy.

The reasons for this are:
1) If charged from a home PV solar system, there is an electrical conversion inefficiency associated with changing the total solar output voltage (typically, about 17 vdc peak per solar panel, and 600 vdc max allowable per series-connected group of panels, determined at maximum cold conditions) to the input voltage required for the storage battery. If the battery was being trickle-charged, we might hope to achieve 95% conversion efficiency in the DC-DC converter, but since it will be charged at relatively high currents during peak daylight hours there will be higher ohmic losses and we can more realistically expect conversion efficiencies in the 90-92% range . . . let’s use 91% efficiency here.
2) If charged from the grid, say during the night with supposedly cheaper, off-peak electricity prices, there will still be an AC-DC inverter loss from charging the storage battery (DC) using grid AC. The best AC-DC inverters have about 97% conversion efficiency, so let’s just use that.
3) But wait . . . getting the storage battery charged is only half the story . . . one will want to use the electrical energy stored in the battery. So, on the output side we will need a high-power DC-AC converter, with a typical conversion efficiency of around 95%.
4) But the battery itself is not 100% efficient in outputting the energy that is fed into it for storage: chemical process inefficiencies and internal ohmic (self-heating) losses mean that only 80-90% of the input energy can be recovered (https://en.wikipedia.org/wiki/Lithium-ion_battery ). So, let’s be very optimistic and say that we lose only 10% of the stored energy here (i.e., 90% storage efficiency) by using only the best battery type.
5) Still not done. These relatively large, high power batteries need thermal management sensing and control systems, as well as safety systems (e.g., to lock out cells that might fail in an electrically-shorted manner), to perform reliably across the range of operational temperatures they may experience. This will involve parasitic losses of around 1% for low- and high-temperature extreme environments, so let’s assign an average 99% efficiency for this.
6) And finally, we need to account for the fact that lithium-ion batteries, like all other chemical-based electrical energy storage batteries, have self-discharge (aka “leakage”) rates. The previously-referenced Wikipedia article gives a value for this factor of 2% per month for lithium ion batteries.

So, using the above efficiencies, we can estimate the total losses that home storage battery use might involve on a monthly basis:
For a storage battery based on charging from a home PV system: 0.91*0.95*0.90*0.99*0.98 = 0.755
For a storage battery based on charging from the grid: 0.97*0.95*0.90*0.99*0.98 = 0.805

Thus, somewhere between 20 and 25% of the total energy input into the home battery storage system will be lost each month. If the average home’s 867 kWh per month all passed through the storage battery, that will represent dumping the heat equivalent of 5.7 to 7.1 kW into the environment each and every day (equivalent to leaving 60 to 70 100-watt light bulbs on continuously!). Even if the home battery storage system only provided 10% of the monthly electricity usage, we’re still talking about dumping 600 to 700 watts of waste heat into the environment each and every day for each and every house using such a system.

So now let’s talk about global warming!

Reply to  Gordon Dressler
January 1, 2019 6:03 pm

…and there are millions of houses, offices, businesses, etc

Reply to  Gordon Dressler
January 1, 2019 9:42 pm


January 1, 2019 5:35 pm

I just watched Timmer explaining why sea levels are different around the globe. It was OK until his last sentence came out of nowhere – he had not demonstrated anything to that point about human-caused global warming – but then he ended by saying that human activity is causing sea levels to rise. He never made the slightest mention of the 400 feet that sea level rose at the end of the Ice Age or that sea level had been higher earlier in the Holocene interglacial. When you claim to be authoritatively explaining sea level rise differences and you don’t place it in historical context – you omit key information – that is rightfully called lying, lying by omission.

January 1, 2019 5:37 pm

I’m more than happy for people to have battery-buffered power supplies in their homes, and to go ‘off-grid’, if they can afford to. I’m happy to do that myself. I like the technology, it is cool, it is the future, *if* it becomes economic for the poor to afford it, and it is, or can remain low pollution tech.

Big ask, and very doubtful at present.

But let’s stop pretending it’s about reducing emissions, or saving the planet, or some such sophomoric twaddle, because it sure isn’t. It’s only about buffering your power supply at great cost, and with potentially tremendous levels of pollution imparted to the planet, if done wrongly, or for blind and ideologically stupid reasons, without thinking it through.

The well-intended mass dictum for Chinese people to kill sparrows during Mao’s Cultural Revolution, to stop the birds from damaging crop yields, produced an explosion in insects which totally destroyed the crops instead, and many millions of Chinese people starved to death as a result.

Mass adoption of batteries to buffer domestic power supplies can produce some very ugly environmental consequences down the road.

Reply to  WXcycles
January 1, 2019 6:04 pm

…and burn your house down

Wiliam Haas
January 1, 2019 6:48 pm

To be totally green, the batteries, solar panels and other related equipment must be made and installed entirely without the use of fossil fuels. Such is not available.

January 1, 2019 9:46 pm

Maybe someday when batteries or a super capacitor is 10x cheaper and last 10,000 cycles will this truly make sense. That day will arrive, but by then it may not be needed if we have a super hardened grid and an atomic nuclear electricity supply of some type that makes electricity truly affordable. Or perhaps a NG fuel cell hybrid electric car that is plugged into both the grid and a Nat Gas pipe, then maybe that could be part of a super hardened grid where every house is a its own mini utility buying and selling electricity.

Right now the losses alone really don’t justify it, and if the the Utility is going to use my battery to assist in buffering their grid, then who pays for my battery cycling? If I do so myself to buy cheaper electricity in the middle of the night for eg, then will it cover the round trip losses and the cost of limited battery cycles? Same thing if they or myself use my electric battery from my pure EV. It may be a good idea in theory, but may not be practical in the final analysis, or even cost worthy. Perhaps for some locations or stand alone applications but then that is still a marginal application. If it makes financial sense without subsidies, then it may get traction, but I doubt it.

January 1, 2019 10:22 pm

This is a pretty old article.

The WUWT title above says
Megan Geuss – 12/28/2018, 4:59 PM

The ArsTechnica article says
MEGAN GEUSS – 2/4/2017, 4:35 AM

The actual study was published
30 January 2017

January 1, 2019 10:28 pm

Please ignore last comment, I was looking at the wrong article.

John Hardy
January 1, 2019 11:33 pm

Nuts to CO2 emissions. Follow the money. I have solar. In the UK, my utility company charges me 3x as much per unit as it credits me for each unit deemed exported to the grid (there is a government bribe, err incentive, on top of that which makes rooftop solar economic).

Being a lithium battery fan, I have of course considered battery storage. However my solar array is not big enough to make battery storage sensible at these northerly latitudes. I only produce a few units a day, so any time shifting capability needs to have low capital costs to make it viable. Cost for new batteries is too high at present.

That may change if two things happen. Firstly. if efficiency of solar panels improves to the point that I can produce a goodly proportion of our daily consumption even in winter on a cloudy day. Secondly if a market develops in second life EV batteries. For an EV, battery capacity is critical. For this application who cares if capacity is down to 80% of the original? If you don’t have enough capacity then (metaphorically) raid the scrapyard for another used battery.

A final note. Of widely-available chemistries, lithium ion is the best fit: partial charge and partial discharge suits it very well but lead acid prefers to be fully charged regularly

January 2, 2019 12:52 am

You have to understand the logic that drives the idea of the residential battery.

The Party Line consensus on Ars is that we are heading for a gobal warming disaster. So naturally the hand picked commenters look feverishly for solutions. The Party Line is that renewable energy for electricity generation is a big chunk of the answer.

This is because renewables appear to give the hope of limiting emissions without serious changes in lifestyles. We will continue with the freeways and suburbs and air conditioning, it will just be powered by wind and solar.

It then becomes necessary to have batteries to power all those electric cars which are going to be plug in replacements for ICE. Spearheaded by the immortal Musk and the great Tesla Corp, which is obviously the future of transportation.

And on generation, Ars is caught in a dilemma from which batteries are an escape route. On the one hand it wants to claim that their intermittency doesn’t matter in modern grids. In some unexplained way, its supposed not to matter when the electricity is generated. There is no longer any need to match supply and demand. Yes, you will actually get a chorus of assertions of this if you read the comments. People really do claim to believe this.

They are then able to argue for Levelized Costs as a comparator. The Party Line at Ars is that fossil fuels are economically dead, because renewables are now cheaper. To support this position they have to be one of the few places in the world defending the use of Levelized Costs as a measure of comparison between different generating technologies.

In order to make this even halfway plausible, you have to believe in free or cheap storage, and if you can manage to believe that everyone is going to install residential storage batteries powered by wind or solar, you would be sort of home free. Because then you do not have to add storage costs in the grid, which, if you do, immediately takes the cost of wind to well over double that of fossil fuel generation.

It makes absolutely no sense. Its impossible to summarize without seeming to parody it. Its full of contradictions and non-sequiturs. But this really is the Ars Party Line. If you have to summarize it in one line it would be something like this:

Intermittency is not a problem and batteries are the solution to it.

The fact that this relatively common sense and specific piece has appeared, correctly pointing out that residential batteries are not the solution to anything, is a very interesting sign that maybe the owners of Ars, Conde Nast, are waking up to a need to back off from the Party Line. Another sign is their interesting lack of coverage of the latest IPCC material.

Pretty soon we will always have been in favor of thorium, or fusion. And CO2? Oh, that was so millennial!

January 2, 2019 1:31 am

The central thing to notice in order to understand the social phenomenon of global warming hysteria is this.

The measures most fanatically advocated will make no significant impact on the total of global emissions. And the measures which would make such an impact are not simply never advocated, if proposed, they are furiously rejected.

Example of the first: Paris, installing wind generation, electric automobiiles. Example of the second: actual tonnage reductions from China and/or India, Indonesia etc. Global abolition of the ICE.

Think long and hard about what could be the most likely cause of this insistence on advocating things that can not work, while refusing to advocate things that would.

January 2, 2019 2:38 am

I’ve published a study of the poor economics of using battery storage alongside roof-mounted solar generation in the UK.

It doesn't add up...
Reply to  Capell
January 2, 2019 4:26 am

Excellent analysis.

Gordon Dressler
Reply to  Capell
January 2, 2019 8:05 am

Well, Capell, your published study addresses the life-cycle economics of residential battery storage without any consideration of the actual energy storage and use inefficiencies of the system.

Caveat emptor . . . it is worse than you concluded.

Reply to  Gordon Dressler
January 2, 2019 8:37 am

That was the objective of the paper, to stop people donating money to solar/battery-storage spivs.

As for the system at large – well that’s an even bigger mess. Right now Gridwatch is quite entertaining: all the nuclear, CCGTs and coal flat out, solar and wind delivering precious little, Netherlands interconnector at zero, Ireland taking half a gegawatt, and UK load rising . . .

Peta of Newark
January 2, 2019 5:23 am

Sorry, I’m struggling to wee what they’re talking about.

My take on it is that ‘some’ folks might install a battery to fill with cheap electricity then re-sell it later when prices are high.
No mention of solar panels or consumer generated power APART from here:

While most solar panel owners prefer not to maximize self-consumption because it’s more cost-efficient to sell electricity back to utilities under net metering, utilities have been pushing back on requirements to buy back solar power from residential customers

Then inside that quote, they misunderstand what net metering is – you DO NOT sell surplus electricity under a net metering scheme. You give it away and let your meter run backwards. Then at month-end, you only pay for what you actually consumed/used.

Net metering here:

So installing a stand-alone battery (without solar panels of your own) as they seem to be saying is no more than playing on the stock market or gambling in a casino.
And every time you place a deal or a bet, you lose 10% of your stake through battery & conversion losses – even before the utility and/or Government move in for a piece of the action.

Quite insane. Why would anyone do it – You Are Going To Lose.
You are up against Professionals who know what they’re doing = Making Money and they will milk you.
Making Money is what they do. Electricity supply is entirely incidental to that

Peta of Newark
Reply to  Peta of Newark
January 2, 2019 5:25 am

cracks up with tears in eyes

wee = ‘waste electrical equipment’

What a beautiful Freudian – I amaze myself sometimes

January 2, 2019 7:59 am

In the UK solar rooftop generation is not economic without subsidies. If costed correctly, with discounted cash flow analysis at sensible rates, the payback period stretches to between 15 and 20 years – good luck with that. Adding a battery to this financial disaster just increases the financial loss.

But of course, they’re great bragging rights at London dinner parties.

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