Yup. But in any case, not good for saving money with a battery.
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Does a battery ever have a positive ROI with net metering
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Transformer
Do the math. Save the world. — Mark Leon
* With a battery and a backup interface to cut over to it in a grid outage, the solar panels can stay online, powering the house and battery indefinitely, if you don't use too much energy.
I don't know if all solar + battery systems can do that. Our Solar Edge system can but I hope to not have to test that. It will only power the "essential circuits," so no HVAC or EV charging.
* DC coupled batteries are more efficient since the solar power can go into the battery and back out to the house or grid without converting DC to AC to DC to AC.
* I bet NH will require TOU rates within a few years.
I don't know if all solar + battery systems can do that. Our Solar Edge system can but I hope to not have to test that. It will only power the "essential circuits," so no HVAC or EV charging.
* DC coupled batteries are more efficient since the solar power can go into the battery and back out to the house or grid without converting DC to AC to DC to AC.
* I bet NH will require TOU rates within a few years.
Yep, which is why I have 30kw of solar, 90 panels! I can be off grid 100% for like 6 months of the year with my 7 batteries. BUT, still no ROI for any of this. I will not either live long enough, or be in this house to ever recover BUT is sure is nice to heat and cool my house with my heat pumps to ANY temp all year long, and with zero cost.
nwdiver
Well-Known Member
There is now if you're clever enough. I just bought a pallet of solar for ~$0.25/w. You can get UL rated batteries for ~$200/kWh and a hybrid inverter for <$5k. So the materials cost of 30kW of solar + 70kWh of storage would be ~$45k. ~$32k after the FTC. That would save >$3k/yr. More and more each year. That's less than ~10 years for it to pay for itself. Less than 5 years in a place like CA with high electric rates.
We should just all work to get the POCO's to raise rates as much as possible
I have dollar for dollar net metering but not kWh for kWh. I have to buy at a rate roughly double what I can sell for (about 14¢ vs 6.5¢) because my utility pays me only the generation fee, not the transmission fees when I export.
What this means is that there is some economic benefit for my battery even in self consumption mode, because every kWh I can avoid buying by charging my battery and using it later is worth about 7.5¢, the difference between the two prices.
I presently have one Powerwall Plus, so if theoretically I lived in a sunny desert and avoided buying 10 kWh of grid electricity per day after the sun went down, then that's $300 per year. Not a lot, but not nothing.
But get an EV and options expand even more. If you're home when it's sunny, now you can charge you car also with excess solar, and every kWh saves you the same 7.5¢. This is what I do when it's sunny and because the cars have so much more capacity (and my family uses them) we can almost always charge them more. Only after cars are charged (if home) and the Powerwall is charged will I sell electricity back to the grid.
What this means is that there is some economic benefit for my battery even in self consumption mode, because every kWh I can avoid buying by charging my battery and using it later is worth about 7.5¢, the difference between the two prices.
I presently have one Powerwall Plus, so if theoretically I lived in a sunny desert and avoided buying 10 kWh of grid electricity per day after the sun went down, then that's $300 per year. Not a lot, but not nothing.
But get an EV and options expand even more. If you're home when it's sunny, now you can charge you car also with excess solar, and every kWh saves you the same 7.5¢. This is what I do when it's sunny and because the cars have so much more capacity (and my family uses them) we can almost always charge them more. Only after cars are charged (if home) and the Powerwall is charged will I sell electricity back to the grid.
GregBallantyne
Member
Grid is grid. Batteries are a very wise investment if your goal is energy reliability. ROI might not even make it onto the goal list for many people. It didn't appear on mine.
As I said, if one has extra money that is not putting food on the table, or gas in the car, fun TOY, but, ..
GregBallantyne
Member
But it can avoid putting gas in a car. I no longer do that, for example. Another factor to consider.... my own ROI calc for my entire system moved into "maybe I'll live to see it" territory when I threw in the cost of the Tesla car, the PWs, and the Solar Roof. Without the PWs, the date moves on out again. So, while batteries may not support a feasible ROI on their own, they can contribute to to an overall situation that reaches a feasible ROI when combined with other investments that enable the avoided cost part of the calc to get significantly larger. Especially if net metering isn't in the picture, or even if it is - but then disappears.
Every case is different though - my own did not involve a loan, and that always helps bring an ROI a little closer.
GregBallantyne
Member
But I should also add that the much larger factors in my perhaps semi-delusional ROI calc were the future avoided costs of purchasing gasoline, and future roof replacements. The second due to Solar Roof, panels wouldn't be able to claim this the same way. The PWs are enablers of the rest.
I've said before and I'll say again that trying to calculate ROI for batteries even on NEM2.0 in San Diego with near $0.90/kWh summer peak rates weren't a factor for me at all. For folks with Model S cars or simply a bit of $$, I think sweating an ROI calculation with an unknown future is a waste of time.
If you can afford it, batteries simply give you control in a range of scenarios, all bad for utility consumers (cyber power grid attack, storms, utility decides to cancel net metering (this is happening in a lot of states in general, we get $0.13/$1 net metering now in NEM3.0 SDG&E), forced ToU rates, utilities can raise bypass charges for any pull from the grid, etc etc etc.
Once you toss ROI out the window, decide if any of those benefits resonate with you since no one knows the future. I assumed none and lastly, laws can change like this proposed monthly income thing in CA. Charge everyone another $50-$130/month, cut rates by 1/3 for now (then raise both fixed/usage fees later), and solar alone can be not worth it even.
Since you're on Enphase now, you can also look at their complete solution if you want to hook up a generator to your batteries so it can charge it if there is no sun for long periods. That's an already released/working product. V2H is slated for 2025 now I think (delayed). Maybe the whole NACS thing.
If you can afford it, batteries simply give you control in a range of scenarios, all bad for utility consumers (cyber power grid attack, storms, utility decides to cancel net metering (this is happening in a lot of states in general, we get $0.13/$1 net metering now in NEM3.0 SDG&E), forced ToU rates, utilities can raise bypass charges for any pull from the grid, etc etc etc.
Once you toss ROI out the window, decide if any of those benefits resonate with you since no one knows the future. I assumed none and lastly, laws can change like this proposed monthly income thing in CA. Charge everyone another $50-$130/month, cut rates by 1/3 for now (then raise both fixed/usage fees later), and solar alone can be not worth it even.
Since you're on Enphase now, you can also look at their complete solution if you want to hook up a generator to your batteries so it can charge it if there is no sun for long periods. That's an already released/working product. V2H is slated for 2025 now I think (delayed). Maybe the whole NACS thing.
Transformer
Do the math. Save the world. — Mark Leon
Ditto. I put in a battery to ride out the increasingly frequent outages. It also has "psychic rewards" for helping reduce peaker-plant pollution and rolling blackouts. It reduces peak TOU use but I don't try to calculate the $ROI.
I did try to calculate the marginal cost of electricity to compare against charging our cars in public parking garages when convenient, but it's obfuscated by NEM 1/2/3 rules with storage and CCA mods, PG&E bills and monthly/annual true-up statements loaded with industry acronyms, summer/winter peak/off-peak rates ("tariffs"), and average monthly wholesale rates for net exports. The bills and true-ups don't match the rates. Explanations of NEM rules don't say whether they're for 1, 2, or 3. The bills don't match the rates.
I did try to calculate the marginal cost of electricity to compare against charging our cars in public parking garages when convenient, but it's obfuscated by NEM 1/2/3 rules with storage and CCA mods, PG&E bills and monthly/annual true-up statements loaded with industry acronyms, summer/winter peak/off-peak rates ("tariffs"), and average monthly wholesale rates for net exports. The bills and true-ups don't match the rates. Explanations of NEM rules don't say whether they're for 1, 2, or 3. The bills don't match the rates.
nwdiver
Well-Known Member
Our electrician invested ~$5600 in their battery and it's saving them ~$90/mo. So their battery is helping to put food on the table. No gas in the car though. Both cars are electric. They don't waste $$$ on silly things
GregBallantyne
Member
Nothing at all.... didn't get that granular. It's a bit of a delusional exercise. Perhaps undertaken in an attempt to come up with something when the subject comes up. I think the elements of the basis can be defended, but I certainly may not have captured everything. Probably the PWs don't actually have as much an effect on an ROI as I want them to. But in my experience with Tesla products, not a lot of fixing is required. I know there are other experiences....
The problem with backup is I use 50Kwh a day on average In winter. House is entirely electric. Geo thermal heat etc. spring / fall is 30kwh a day and summer ~40kwh a day.
We work from home. My Model S 2.5 years old and has 16K miles. And I expect that driving rate to even go lower. So cutting our driving during/charging during power fail won’t save much. There is no overage to charge batteries with in winter.
So let’s say I can conserve during power failure. To 30 KWh (most of that being heat). That would be ~3 Power Walls that could run the house for 1 day. Plus splitting up panels and putting in a switch. Tesla estimate says $30K. And Tesla states 15hrs backup with 100% backup and 72% consumption rate in winter.
Chances are a snow storm would be what knocks out power and covers panels that won’t generate all that much in winter even if they were clear and sunny. Average production in January was 5kwh a day. So much for charging up those batteries on Solar.
Battery backup for short power outages is a nice perk. So I still have to have a Generator.
Even at that size, and I assumed I could fully charge (with overage) and fully use 30kwh a day ((I only use 40 kWh for the whole day in summer) for 6 months at double the electricity cost. It would take 65 years to break even. And that’s the most optimistic calculation because no way I could utilize that much battery. Optimum would probably be 2 powerwalls. But that’s like a whopping 9 hrs of backup.
If TOU does come to Eversource NH then that could change numbers drastically.
I do have a request for quote from my Enphase installer but I expect them to be 50% more than Tesla. Enphase does warranty their battery for 15 years.
Also in my calculations I didn’t figure in any battery degradation.
We work from home. My Model S 2.5 years old and has 16K miles. And I expect that driving rate to even go lower. So cutting our driving during/charging during power fail won’t save much. There is no overage to charge batteries with in winter.
So let’s say I can conserve during power failure. To 30 KWh (most of that being heat). That would be ~3 Power Walls that could run the house for 1 day. Plus splitting up panels and putting in a switch. Tesla estimate says $30K. And Tesla states 15hrs backup with 100% backup and 72% consumption rate in winter.
Chances are a snow storm would be what knocks out power and covers panels that won’t generate all that much in winter even if they were clear and sunny. Average production in January was 5kwh a day. So much for charging up those batteries on Solar.
Battery backup for short power outages is a nice perk. So I still have to have a Generator.
Even at that size, and I assumed I could fully charge (with overage) and fully use 30kwh a day ((I only use 40 kWh for the whole day in summer) for 6 months at double the electricity cost. It would take 65 years to break even. And that’s the most optimistic calculation because no way I could utilize that much battery. Optimum would probably be 2 powerwalls. But that’s like a whopping 9 hrs of backup.
If TOU does come to Eversource NH then that could change numbers drastically.
I do have a request for quote from my Enphase installer but I expect them to be 50% more than Tesla. Enphase does warranty their battery for 15 years.
Also in my calculations I didn’t figure in any battery degradation.
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I think it's just silly to assume having batteries alone will be enough/useful for anything other than ToU shaving, less peak grid use or outage usage. A week of no sun makes any battery setup dead in the water really (after 1 day). There could be storms, clouds, fires (in CA). Batteries alone will never be enough. You need another power source and the ole generator is still great for almost all those cases at a cheaper cost. Generators need maintenance though, are dirty, noisy, tells everyone you're running a generator, etc, but they do the job for longer term outages and it's the only solution currently I've seen here from following it here and everywhere else.
I've stated before and still suggest that folks think a battery will do ROI is wasting their time. Remove that from your equation and measure/value the other non-monetary ROI stuff. Simply, don't lie to yourself or convince the spouse that there is ROI. It makes the purchase so much easier/comfortable if you don't have it and decide after what to do.
I think 50kWh usage daily is a lot. We use like 15kWh or 20kWh daily if we aren't car charging. Of course, if it's not summer, we don't use much power/heat for anything.
This is a bit sideways, but have you looked at adding insulation? E.g. windows, insulated window coverings, attic, walls, etc.?
For winter outages, I think it is either, suffer, or wood heat and candles, or a generator. The latter requires a transfer switch and does not play well with Powerwalls, at least currently. (Not that I see Tesla changing that.) Enphase is, I think a better choice, as Enphase can turn on a generator, charge batteries, and then turnoff the generator. Just my $0.02...
All the best,
BG
It’s a brand new Post and Beam with SIP panel roof and walls (solid foam). With GeoThermal it cost $150 to heat in January. The only fossil fuel I use is Propane for Generator and BBQ. It also has an ERV system because it’s so tight we’d poison our self’s without it.
You can see the SIP
This is the 15Kw Enphase Solar
So where would I put the added insulation again
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