Do any of you have experience with home battery backup systems? I live in California (home of the PG&E rolling blackout) and have leased solar panels that are tied to the grid. I have a 700 kW dual fuel generator that can power the essential functions in my small house, but it is very noisy and goes through a propane cylinder in about 3 hours.
I’m considering getting a backup battery system that would
Reduce my grid electric usage during the peak pricing window and
Supply quiet, efficient power in an emergency.
My solar provider (Sunrun) advertises that they will lease Powerwall batteries at $40/month.
If you have a battery backup system, have you found it to be reliable and trouble-free? Do you think it was worth the extra cost?
I can’t answer your battery-related questions. But considering just this bit …
Have you considered getting a much larger propane cylinder, like the 500 gallon ones? Might be cheaper than you think. Contact whoever sells bulk propane in your area to ask.
Many California residential areas are plumbed with natural gas. Can you arrange a hookup to that fuel source? When I was living there we had a gas spigot in the backyard for powering our portable BBQ. And another for a portable mushroom IR heater. Instead of hooking the BBQ’s or heater’s hose to a propane tank we hooked it to that spigot and turned on an infinite supply of natural gas. Which supply will also flow normally during a power failure.
Yes, the generator would need to be a NG-compatible model. But the difference between burning propane and NG is pretty much just some new orifices in your carburetor; not difficult.
(Disclaimer: I never had a system of my own, but I used to work in this industry, both for retailers and solar + battery manufacturers)
A couple quick questions for you:
Are you sure your generator is 700 kW, not 7 kW or 700 watts (or perhaps 700 kWh of fuel/energy capacity)? 700 kW would be absurdly HUGE for household use and if it’s really that big, it’s probably not running very efficiently and you’re just wasting fuel. I can’t imagine any normal home, even with several weed farms, using 700 kW of power. A single Powerwall’s off-grid output, for example, is only 7 - 11.5 kW (depending on model), so either you have an extra couple of digits there, or your house is using 100x more power than typical…
Is there any particular reason you’re leasing (instead of buying or financing)? Typically those aren’t great deals for homeowners, since the installer keeps all the rebates and such and you’re often left paying both the rent on the equipment and some portion of the electricity bill. How would adding a Powerwall change your current lease terms, beyond adding $40/mo (like is there a lease extension, etc.)?
I think generally speaking, battery backups can work the way you want, but depending on your household power usage and how long you expect to be off-grid for, it may take a few Powerwalls to sustain that. Like if you just want a few lights on and keep the fridge running, it’s pretty easy to keep that going for many hours. If for some reason you really do have nearly 700 kW of power usage at home, you’re looking at something entirely different (like an industrial battery farm).
Before you buy/lease anything, it might be a good idea to calculate your home’s actual typical power usage (like from your solar monitoring, if you have any, your utility’s website, or various power-measuring devices you can get).
Are you sure your generator is 700 kW, not 7 kW or 700 watts [/quote]
Duh. Thank you, yes it’s 10,000 W startup, 725 W running.
Leasing would be purely for convenience and to get the free maintenance. I assumed the solar lease when I bought the house – it was not financially reasonable to buy out the rest of the lease term. Sunrun would just add $40/month/battery to my bill and they have been pretty good as a solar company.
I noticed that Generac, for example, sells its own brand of battery backups and I will have to investigate how much they want for a 10 kW system. That may be the way to go.
My electric bill runs about $175/month of which peak pricing (at $0.47/kwh) averages about $35/month. My emergency power needs are pretty modest: fridge, microwave, TV, lights & plugs, computer.
I have enough solar panels that I get a small positive true-up from PG&E most years. I’m trying to get PG&E off my back as much as possible. One of the attractions of the battery is that it can be set to kick in during peak pricing every day which would continuously cut my bill. A gas-powered emergency generator just sits around most of the time.
Another reason I’m thinking about this now is that I expect there to be very dramatic and unpleasant changes to the US economy and infrastructure for the foreseeable future and I expect that the price of backup batteries and energy will both increase.
Thanks for the idea, but I’m not seriously considering gas-powered backup. As @Reply figured out, my little generator is 725 W (not kW!). I can lift & store 20 lb propane cylinders, but I don’t have room for a 500 gal propane tank.
I’m rejecting natural gas because I’m trying to get away from PG&E as much as possible. Their NG rate more than doubled just this past year. And a battery can be set to automatically supply power during peak pricing hours. That’s not economically or aesthetically feasible with an NG emergency generator.
If PG&E didn’t control both power sources the calculation might be different!
My brother (the doctah) and his wife (ditto) got a Tesla, a Tesla Powerwall, and solar setup less than a year before Musk went full Loon. For similar reasons to yours - their area in Dallas got off pretty light in the “Snowmageddon” but they like having full house backup power if need be, and as doctors, wanted to be able to more easily maintain communication if they were called in.
Mostly though they use the solar to handle some of the spike in summer A/C and otherwise to feed the car for free-ish charging.
So that combination could work for you. But, in light of modern-Musk, you may want to evaluate if it’s a Tesla Powerwall battery, or one of the less-known competitors. Entirely up to you.
Given all that you said, if the Powerwall is really only $40/mo (and there are no catches? are you sure?), that seems like a great deal and the easiest, no fuss, drop-in solution. If you bought one, it would usually cost $10,000+. At $40/mo leased it would take 20 years to break even on that, so that seems like a great deal IMHO (as long as it’s not too good to be true… check the revised lease terms very carefully!)
You can find cheaper battery backup options out there, but IMO what you’re really paying for is peace of mind anyway, so if the Powerwall works well with your existing provider and equipment, that seems like the easiest option. Be sure to test it in off-grid mode though, BEFORE an actual outage, to make sure everything works the way you expect it to. It does suck that Musk has gone off the deep end, but hey, if anything, I guess he’s double-incentivized to both cause the apocalypse and sell you protection from it… /sigh.
Generally, the underlying batteries are chemically similar to each other, and often made by the same few OEMs anyway. So what you’re paying for between different brands is the rest of the system (all the electronics that control charging and switching and monitoring and such) and importantly also the attached app, if any. Some are much easier to use than others. I’d try to get a demo of that if you can, and also specifically ask about what happens when the power goes out (like does it automatically and seamlessly switch over to backup mode, or do you have to physically flip a transfer switch or toggle something in the app, etc.). And what happens if the internet goes out – can the app still communicate with the battery, or does the battery itself have on-device physical screens and buttons so you can switch modes and such as necessary?
PS Just so you know, there are also cheaper, smaller portable options like Anker SOLIX F3800 Portable Power Station - 3840Wh | 6000W - Anker US (also available as a kit from Costco). Those are good if you don’t want a permanently installed one for some reason (like you could take it with you if you need to bring it to a friend’s house or to some refugee center in case of a bad fire).
But they’re not as big (long-lasting) as a permanently installed one, and generally won’t be able to do time-of-use load-shifting (the “buy low sell high” electricity arbitrage you mentioned) .
If you’re not too concerned about needing to take your backup power with you during an emergency, the permanently installed kind makes more sense.
It sounds like @Bone really liked his system! I wonder how well it has aged?
Oooh, thank you! That’s what I wanted: someone with recent experience.
The thought of using any Tesla products makes me barf, but if I go the path of least resistance and lease the batteries from Sunrun, I don’t have any choice.
Thank you for the caveat. I won’t rush into anything
Thanks again – this is something I hadn’t considered. It would be really nice if there were manual alternatives for all the apps I have on my phone!
Heh, heh. That’s actually what started me thinking seriously about battery backups: I got my Costco flyer in the mail advertising the Anker SOLIX F3800 On Sale. Then I looked at some of the reviews & users were saying the supplied solar panels only charged the batteries to about 50%, and you had to charge them from 120V house current to get a full charge. And that only their solar panels will work with their batteries. And that they will sell you solar panels that will charge the unit fully, but at significantly more $$.
That was when I started researching whether it wouldn’t be better to tie battery backup seamlessly to my existing solar array, which I think is the way to go if the lease terms are good.
Hah, that would’ve been great if a trade worked out No worries though. I honestly miss the renewables industry and I miss geeking out on all that. Happy to answer whatever questions I can, though I’m not an expert, just a worker who absorbed some of through osmosis. And it sounds like you got it mostly figured out anyway.
As much as I hate to admit it, the Powerwalls do seem the most mature to me =/ I am not sure what other companies I would trust. Maybe Enphase and SolarEdge? Kohler’s in the game now too, but like Generac, they came from the generators side of things, so I don’t know how good their products are or aren’t.
I’ll just say, regarding the generator, that when I was in the country I had a 6kW running gas generator, and I could get a day out of 5 gallons of gas. To be fair, I’d shut it down when I was at work.
On the note of generators – not that one should replace battery backup, but it’s nice to have an extra backup in case of a true emergency – it’s not clear to me whether anybody actually makes a home generator that small (725W). Perhaps it’s 7.25 kW (7,250 W) running…? That’s a much more common size.
But if that’s the case (if it’s actually 7250 W), and the OP is only powering a few devices:
My emergency power needs are pretty modest: fridge, microwave, TV, lights & plugs, computer.
That likely means the generator is still barely doing anything – and thus running very inefficiently, and most of the fuel is being burned just idling. All of those power draws combined, minus the microwave, would struggle to reach 200 W (or barely 3% of a 7kW generator’s output). The microwave is the challenging one, because most of them use a lot of power (750 W - 1,500 W) at full blast, but only for a few minutes at a time. It’s hard to size a generator to accommodate small bursts of that AND sustained continuous low draw from the other devices & lights.
It may be more efficient to, say, use electricity for the low continuous draws (everything other than the microwave) and to have a separate propane cooktop (or butane, like the camping kind). It’s hard for generators & batteries to keep up with cooking, but easy for fossil fuels.
They also do make both inverter microwaves and inverter generators that can step down to lower power without losing as much efficiency. But if OP is going to get whole-house battery backup anyway, just having any generator (even if oversized) is already a lot more prepared than not having one at all.
It’s actually the other way around. I just went out & checked the generator again. It says 10,000 starting watts and 7250 running watts (my excuse is that a flap had covered over the last 0, but I still should have realized this was too big a difference between starting and running)
. Aaarrrrgh! I swear to FSM, I don’t know how I passed that IRS tax exam (luckily, TaxSlayer [great program, BTW] finds a lot of idiot errors like that).
To be honest, the propane tank wasn’t empty when I stopped the generator, but it was significantly lighter, so I don’t know how much longer it would have run.
Lol, the irony is that @bobsmom101 is helping me over at another numbers-heavy tax thread.
I mean, I get it. Add a dollar sign in front of otherwise ordinary numbers, and my eyes just unavoidably glaze over. Add kW to the end, and I guess the same thing happens to them
To be fair, though, the watt and kilowatthour are totally crazy units that should be banished from existence. Confuses everyone. In school we had a homework assignment to find W/Wh/kWh errors on supposedly informative websites, and there were so, so many…
Now I wonder… is there maybe a way to charge the battery backup (Powerwall or similar) from the generator? I mean, I wouldn’t just plug the generator into an outlet with the battery backup installed… that might blow something up… but I wonder if there’s a right way to do that. Just in case, I dunno, the sun dies or something.
Can you even use a generator if you have a battery backup system installed…? (I’m not sure how you’d safely connect the generator to the home circuit in that case).
No worries though. I honestly miss the renewables industry and I miss geeking out on all that. Happy to answer whatever questions I can, though I’m not an expert, just a worker who absorbed some of through osmosis. And it sounds like you got it mostly figured out anyway.
