I’m in process on a 12.24kW system with three power walls at a cost of 48100 before incentives. I see how difficult it is to add power walls after the fact due to scarcity and Tesla requiring additional panels with the power wall. I’d really like to extend my reserve storage / backup storage to handle extended outages and consume less grid energy. i don’t have enough roof space to add additional panels or I’d do that too but with PW being $4810 after tax incentives and I have a 0.9% loan I’d like to get the fourth wall. Is there any reason not to other than the expense, which I am not concerned with.
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Thoughts on additional power walls
- Thread starter Zer0t
- Start date
I have 5 PW's. If one can afford, they are a fun toy to play with. I still will never tell anyone it makes sense. Generator, IMO, is much more cost effective. We cannot take our money with us, so why not. For what one high end Tesla costs, I have tons of solar and generator.
jrweiss98020
Tessa's Tesla
Sorry I’m a newb so I don’t understand what you mean. Are you speaking continuous output? Your auto signature gave me a chuckle.
I believe they are rated 5 kw continuous output. At least with PGE, if you go over 30 other stuff might come into play. So with 5, thats 25kw. My panels are like 29kw
But, if I had a choice of more panels vs batteries, I would do panels as I did. I need to be able to charge as much as possible in winter since I have heat pumps. But whether PGE will approve this additional 15KW of panels I put on is a wait and see.
I did the math on a 8.6kW PV + 1 Powerwall 2 vs 11kW standby whole home generator. Between electricity offsets and production incentives the PV will pay itself off in about 9 years. When I then compared just the Powerwall vs the standby generator the Powerwall came in at $12,221 and the generator came in at $12,184. That may sound close but the Powerwall had a 30% federal ITC making it actually $8,554.70 and the generator quote did not include the gas piping, which was estimated at about $2,000 + tax. I also looked in to getting a portable generator which, to your point, was much more cost effective.
The net comparison was:
Powerwall @ $8,500 net outlay
+ Provides backup protection 100% off grid, including natural gas "grid".
+ No regular maintenance
+ Running while the grid is down is free
+ Instant switchover during an outage
o Unlimited runtime during the summer, limited runtime during the winter
- Not be able to back up everything
Generator @ $14,500 net outlay
+ Provides whole home backup protection
o Unlimited runtime while fuel is available
- Takes a minute to switch over during an outage
- If natural gas is unavailable, generator doesn't work (ie long term power outage, earthquake, etc)
- Costs $1/hr to run, $250/year to maintain
I went Powerwall
@gpez how many power walls?
I got bad news changing my order for more power walls would delay me 6-9 months. Is there anyway to get them installed ‘ added after the base system is done?
my generator quote was 15,500 with gas plumbing and 9 month wait for the unit. I wanted solar anyway so this is just a natural add on.
I got bad news changing my order for more power walls would delay me 6-9 months. Is there anyway to get them installed ‘ added after the base system is done?
my generator quote was 15,500 with gas plumbing and 9 month wait for the unit. I wanted solar anyway so this is just a natural add on.
Yes. We had 3 Powerwalls installed in 2018 and a 4th Powerwall installed in 2019. It didn't take very much work to add the 4th since we planned for it originally.
Unfortunately, our 4th Powerwall did fail the initial inspection since the inspector didn't like the additional wiring in the 2018 conduit. Tesla ran another conduit parallel to the first conduit and everything passed inspection.
If you are having them install conduit for yours, I would suggest you have them size it to handle the wiring for all 5 Powerwalls so that you don't need parallel conduit runs.
Sure, you can add a powerwall or powerwalls later, it just will cost more than it costs now. Other than cost of the powerwall, depending on the how your electrical infrastructure is setup in your home, there could be additional costs because of panel feed limits, etc. Thats all "the costs" though, that you said you didnt really care about.
In CA, there is a difference between 2 powerwalls (10kW continuous) and 3 (more than 10kW continuous) from the PTO from the utility perspective. I dont know if your utility in NJ is similar. There is likely not much difference from that perspective from 3 to 4 though.
One can play with number anyway one wants. Had my generator a year and zero cost to maintain so far.I did the math on a 8.6kW PV + 1 Powerwall 2 vs 11kW standby whole home generator. Between electricity offsets and production incentives the PV will pay itself off in about 9 years. When I then compared just the Powerwall vs the standby generator the Powerwall came in at $12,221 and the generator came in at $12,184. That may sound close but the Powerwall had a 30% federal ITC making it actually $8,554.70 and the generator quote did not include the gas piping, which was estimated at about $2,000 + tax. I also looked in to getting a portable generator which, to your point, was much more cost effective.
The net comparison was:
Powerwall @ $8,500 net outlay
+ Provides backup protection 100% off grid, including natural gas "grid".
+ No regular maintenance
+ Running while the grid is down is free
+ Instant switchover during an outage
o Unlimited runtime during the summer, limited runtime during the winter
- Not be able to back up everything
Generator @ $14,500 net outlay
+ Provides whole home backup protection
o Unlimited runtime while fuel is available
- Takes a minute to switch over during an outage
- If natural gas is unavailable, generator doesn't work (ie long term power outage, earthquake, etc)
- Costs $1/hr to run, $250/year to maintain
I went Powerwall
The issue is heating. If you are gas, its totally different than if totally electric, IMO. In winter, if I get an outage thats long, and no solar basically, my PW's will be dead in a day. At least my generator then comes to the rescue
Just one. Couldn't justify more than that. My PV system was installed in October and the Powerwall came in April the next year so yes, if planned properly you can add them later no problem.
Everyone's situation and numbers are different for sure. Your earlier statement was "I still will never tell anyone it makes sense" - I was just offering that in my case it did make sense. I would agree though that for backup power a generator is probably the right call the majority of the time.
Don't mean to sound snarky but if you haven't spent anything to maintain your generator in a year (either time or $$$) then you're probably not maintaining it properly...
Exactly, there are a lot of variables at play and there’s no “right” answer. I don’t know why there’s always so much negativity around PWs vs. generators (not directed at you @gpez ).
For example, my underground propane tank isn’t large enough to support a generator to back up the entire house, so in addition to purchasing the generator I’d have to upgrade the tank (not on city gas). In addition to that, my electric company will pay me more per kWh that my PV generates just for having ESS, and they will also pay me to use some of my battery when the grid is under very heavy loads. Both of those cut down the total cost of ownership for the PW. Wouldn’t get a monthly/annual check if I had a generator…
@h2ofun I’m surprised your generator doesn’t periodically cycle automatically (unless you’re not including gas in your maintenance expenses), all engines have service intervals, so it’s only a matter of time until the bill comes due.
Liked because of your post's content and your username. Hope it came with double prize money.
Did you get a quote for upgrading the tank + running any new pipe? Propane is much more energy dense than natural gas so I'm curious how big you'd have to go to support a standby generator vs Powerwall.
Honestly once I heard new tank, I wasn’t super interested in going forward, so no, don’t know what it would end up costing. There also isn’t a great spot to put a generator beside our house, and I’ve put a lot of work into the front lawn (where our tank is) and wasn’t about to let someone hack away at it
The issue with propane tanks and generators is often how little propane you can extract from even a large tank when it gets cold. E.g. even a 500 gallon dedicated LPG tank maxes out at 15kW at 0F. (That tank would last a little over four days at full 15kW of power.) The tank needs to absorb heat from the surroundings to boil the liquid propane into gas. Check out tables 6&7 here. Table 5 gets into pipe sizing. You need even larger tanks for mixed heat and backup, and having both on one tank is not something that is generally recommended due to the sudden increases / decreases in flow caused by the generator make it hard to have stable pressures for the rest of the house. (Yes multiple regulators help solve the problem, but most installers that I know prefer two tanks to (?) simplify things and ensure that there is still how after and cooking gas available.) I have heard more than a few stories of homeowners running their tanks empty during outages because they didn't appreciate the rate at which generators use fuel.
Our propane supplier flat out told us that if we went with backup generator powered by propane, not to expect refills during a disruption, and we should plan to have enough propane to last for the duration. (You might also want to check with your homeowners' insurer about how much propane they are comfortable with having on site. It might be smaller than you think.)
All the best,
BG
Why? It runs like once a week for is maintenance mode. I am not even close to needing the oil changed yet. So, what am I not maintaining correctly?
Yep, it cycles like each two weeks. So yep, at some about of time, it needs the oil changed, but not close to it yet. Bill comes due? Never said free but to say 250 per year is nothing I am seeing
My tank is 500 gallons. Now, for me, when I use the generator, I do NOT keep it running 24/7.
