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Is 1 PowerWall better than No PowerWall?

h2ofun

Active Member
Aug 11, 2020
2,430
415
auburn, ca
I am in a similar situation, would like PW, but just too hard to justify the costs. I thought about doing just a single, like you suggested, but decided at this point it was much easier to adjust my usage during peak hours. We have had maybe 6-8 power outages in over 10 years, most of those were resolved within a couple hours, so not much of a need for backup power. I have an older solar array that is just over 10 years old, so plan to revisit the PW in a few years. At that point It might be worth while to replace my old system and add the PWs.
If you are on PGE tou-c, the difference in price between peak and non peak is so small, I have never worried about changing my usage
 
Mar 15, 2021
171
64
California
I've been going back and forth on whether to get PW or not. I'm in SoCal, with SCE and plan to get 8.16 kW solar panel.

The prob is 2 PWs' ROI will take too long to recoup the cost. My goal of getting PW is to offset peak hour usage, not for blackout. From what I have read in last few months, SCE doesn't provide 1:1 NEM. During peak hours, i have to pay more and only get wholesale price for the over generating power.

Can I just go with one? Is 1 PW enough to offset the peak hour usage? How can I figure this out? My daily power usage is about 17.55 kwh.

Thanks.
I have SCE and one PW. SCE does provide 1:1 NEM for usage. Every kWh you use during peak is credited 1:1 for what you send back. And every kWh you use during off peak is also credited 1:1 for what you send back. But you if you produce more than you use overal they only compensate you whole sale regardless of when it’s produced. And if you consume more than you produce you pay the full retail price; this is where the PW can come in handy as you can run you whole house during peak from the PW and not use any grid power. You will not have to pay a single penny to SCE during the peak and end up making money (whole sale) for sending all solar to the grid during this time.

The other benefit of getting a PW is you can sign up for TOU Prime plan. You cannot get this plan with solar alone. This plan has the cheapest off peak rates.

I have a pool and even before summer started I’m already $150 net credit for the year with SCE. I’m expecting about $500 check from them at the end of my 12 months while only paying about $180 for the year with taxes and fees. So I should actually profit $220 from my production.
 
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h2ofun

Active Member
Aug 11, 2020
2,430
415
auburn, ca
I have SCE and one PW. SCE does provide 1:1 NEM for usage. Every kWh you use during peak is credited 1:1 for what you send back. And every kWh you use during off peak is also credited 1:1 for what you send back. But you if you produce more than you use overal they only compensate you whole sale regardless of when it’s produced. And if you consume more than you produce you pay the full retail price; this is where the PW can come in handy as you can run you whole house during peak from the PW and not use any grid power. You will not have to pay a single penny to SCE during the peak and end up making money (whole sale) for sending all solar to the grid during this time.

The other benefit of getting a PW is you can sign up for TOU Prime plan. You cannot get this plan with solar alone. This plan has the cheapest off peak rates.

I have a pool and even before summer started I’m already $150 net credit for the year with SCE. I’m expecting about $500 check from them at the end of my 12 months while only paying about $180 for the year with taxes and fees. So I should actually profit $220 from my production.
What assumptions are you making for his heating and air? Heat pump? Gas? No way from what I have seen with my heat pump use, and I expect with AC, would 1 PW last that long.
 
Mar 15, 2021
171
64
California
If you want to offset or back up 240V appliances then one Powerwall isn't sufficient. For example, if you have 240V A/C, one Powerwall wouldn't be able to handle it. It could offset usage of other 120V electronics.
Only during an outage. One PW can power the whole house as long as the grid is up. I’ve run both my pool pump (240v) and AC (240v) along with anything else being used in the house during peak time from the PW even though those to beakers are not on the PW sub-panel (those are the only 240 appliances I have)
 
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h2ofun

Active Member
Aug 11, 2020
2,430
415
auburn, ca
Only during an outage. One PW can power the whole house as long as the grid is up. I’ve run both my pool pump (240v) and AC (240v) along with anything else being used in the house during peak time from the PW even though those to beakers are not on the PW sub-panel (those are the only 240 appliances I have)
And you are using zero grid power during that times, only 100% from 1 battery? For how long?
 
Mar 15, 2021
171
64
California
What assumptions are you making for his heating and air? Heat pump? Gas? No way from what I have seen with my heat pump use, and I expect with AC, would 1 PW last that long.
He’s in SoCal. I can almost assure you he has gas for everything. Pretty much everyone here does.
 
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h2ofun

Active Member
Aug 11, 2020
2,430
415
auburn, ca
Yes. From 4-9 all battery. I use anywhere from 20% - 40% of the battery during this time (depending if I’m using AC)
How big is your house? I sure use a lot more than that since I have a big, multi story house, with the west sun killing my house in the evening, and reflecting off the lake
 
Mar 15, 2021
171
64
California
So, how long can he run AC in the dead of summer, during peak, when those folks are real hot?
During the entire peak. AC doesn’t run continuously for 5 hours. Plus he can always adjust the prime to start closer to 6:00 during the summer since there’s still plenty of sun from 4:00-6:00 taking a couple of hours off battery usage, using solar and still sending net solar to the grid.
 
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KHYE

Member
Jan 7, 2021
13
2
Los Angeles, CA
I have SCE and one PW. SCE does provide 1:1 NEM for usage. Every kWh you use during peak is credited 1:1 for what you send back. And every kWh you use during off peak is also credited 1:1 for what you send back. But you if you produce more than you use overal they only compensate you whole sale regardless of when it’s produced. And if you consume more than you produce you pay the full retail price; this is where the PW can come in handy as you can run you whole house during peak from the PW and not use any grid power. You will not have to pay a single penny to SCE during the peak and end up making money (whole sale) for sending all solar to the grid during this time.

The other benefit of getting a PW is you can sign up for TOU Prime plan. You cannot get this plan with solar alone. This plan has the cheapest off peak rates.

I have a pool and even before summer started I’m already $150 net credit for the year with SCE. I’m expecting about $500 check from them at the end of my 12 months while only paying about $180 for the year with taxes and fees. So I should actually profit $220 from my production.
Thank you for sharing your real experience, I thought TOU Prime is only available if u have an EV which I don't. Do you have 1 or 2 PW?
 
Mar 15, 2021
171
64
California
If you are on PGE tou-c, the difference in price between peak and non peak is so small, I have never worried about changing my usage
They only have d plans now. With a PW he can get the Prime plan which is $0.16/kWh off peak and $0.41/kWh peak. That’s 2.5 times more between peak and off peak.

Without a PW he has to get either the 4-9 or 5-8 D plan. The 4-9 is $0.27 off peak and $0.49 peak in summer. The 5-8 is $0.27 off peak and $0.54 peak in summer.
 
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Mar 15, 2021
171
64
California
Thank you for sharing your real experience, I thought TOU Prime is only available if u have an EV which I don't. Do you have 1 or 2 PW?
I have only one.

No, you need either an EV, PW, or water or heat pump to get the Prime. I only have a single PW and am on Prime. They default you to the 4-9 D plan. I just emailed them after PTO to request prime. The next month I was switched to Prime.
 
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Mar 15, 2021
171
64
California
You are absolutely correct. I have gas stove, gas water heater, gas dryer.
It was a good assumption. Natural gas lines cover the whole area and is so much less expansive than electricity. Just about every house here has natural gas.

ETA: We also have more natural gas than we know what to do with. We have an entire area in downtown LA where there is tar, oil, and natural gas bubbling out of the ground. They even put a museum there collecting ice age animal bones from these tar pits.
 
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Mar 15, 2021
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tomuo

Member
Mar 15, 2021
19
7
Los Angeles, CA
Anecdote, my situation, 1PW is plenty.
I'm in Los Angeles, SCE as well.
I had 4.8KWh solar installed in 2018, I added 1PW and 1.8KWh of extra solar (West facing) last year.
I'm on the 4pm-9pm TOU plan which in the summer is 3x the off-peak cost.
Solar production is about 40KWh per day now.
Daily home usage is about 30KWh, so 1PW is not quite enough to make me fully self sufficient.
But with the advanced time-of-use scheduling, on a clear day the PW is fully charged by around noon, I'm feeding excess into the grid until 4pm, then both feeding back to the grid from 4pm to around 7pm, and running the house from the PW until 10pm or later

So I'm getting full benefit of the TOU rate arbitrage, and I have the peace of mind of the backup for the odd grid disconnections.
And any time that SCE raises the peak rates, it benefits me.

I expect this to be much better month-to-month that previously with no PowerWall.

Winter months are going to be a bit lean, but that needs more solar, not more PW.
 

Southpasfan

Member
Jun 2, 2019
417
525
Pasadena
As soon as someone says "SCE" I don't know if there is any point in trying all the advance math.

Unless you somehow use what seems to me to be a ridiculously small amount of electricity from 4 to 9, that's going to be five hours at an absolute minimum of 2kwh per hour or 10.

My house runs more than that but bear with me.

Subtracting, I don't know, 65 winter days to make the math easier, and its 3,000 kwh per year at 27 cents or about 60 bucks a month. One powerwall could easily handle 10 kwh day provided the solar system can recharge them. One PW is not more than $60 per month as although the warranty is 10 years they will last longer than that at some level of max.

So you can pay SCE or pay PGE or not pay them and have a cool PW.

Other utilities with true net metering are different. I am in LADWP territory so I could save more without PWs but as I say first, they are cool, and second, no worrys about loss of power.
 

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