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Justifying powerwall cost
- Thread starter Merrill
- Start date
My kindergarten graph explains how I'm justifying it... moving blue power I make with solar to green expensive power I'm buying from PGE is hammering me with.. My solar is pointed the wrong way and completely shaded other than very early in the day (part peak) I make ~20kwhrs a day, and if I take a conservative stab at savings, I'd be saving about $6-7 a day in peak demand shaving, or about $150-200 a month during the summer. So payback in 5-8 years but I also get battery backup.. So that has value as well.
(below is my average power in a day from my enphase inverter reporting)
(below is my average power in a day from my enphase inverter reporting)
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Hmm, so they only charge $300 additional for extra PW. Should I go 2 PWs so I can run AC off it? My grid is pretty reliable though.
roblab
Active Member
Hey, Merrill.
I'm in Angwin, just had 3 powerwalls installed, extensive reworking of main panel, Gateway, etc. etc., cost a little bit more than what you paid. I have 11 kW of solar, old and newer. Sounds like your situation
I don't expect it to pay back for a while, but I can sell peak solar to PG&E. The biggest plus to me is that I can ignore power outages, which are common up here, three already this year, one more than a day long.
I had ordered these nearly two years ago, and the price quoted was $5000 per PW, which they honored.
Hope your PWs and panels help. I've hardly had an electric bill for a dozen years, get a return on true-up most years, and hope it increases. Still need the grid for charging my two cars it seems.
Where do I find information on rebates and tax credits??? Inquiring minds want to know.
Thanks roblab, really need power when PG&E shuts down for wildfire criteria we are on a well so no power no water. Tesla is doing a work up for 2 Powerwalls, we will see what their quote is. So far the non Tesla quotes have a much higher install costs.
There is a different approach to looking at the cost for powerwall. I'm in California USA with net metering. PGE acts a 100% efficient battery so pw for backup is the only straight forward use. However, using powerwall can allow one to displace grid usage with solar power if that is a user preference. 'Cost justifying' in this case just means displacing (substitution) cost. For example, I might buy a Ford instead of a Chevy for the same price. I did not save any money, but exercised a preference for how it was spent.
For me, I purchased a 14 panel system with 2 pw. My analysis shows: using E-TOU-B and being able to fully charge pw off-peak and use pw for all usage on peak (40% of total usage on peak) 1510 kWh/month, if 12% of off peak usage cost can also be offset, over 10 years I break even on cost versus no pw; 12 years with no off-peak offset. PW cost + solar panels cost after incentives is $22,964.09. I use Samsung DVM eco system for HVAC and electric induction range, so heavy on the kWhs, light on gas.
If, instead, usage is 900 kWh/month, it would take 17 years to break even with no off peak offset.
In any case, my point is "cost justify" can include merely not losing money as an expression of user preference with a bonus of backup power. Saving money is not the only issue. Each situation is different and requires its own analysis, but powerwall should not be dismissed just because it might not save money.
For me, I purchased a 14 panel system with 2 pw. My analysis shows: using E-TOU-B and being able to fully charge pw off-peak and use pw for all usage on peak (40% of total usage on peak) 1510 kWh/month, if 12% of off peak usage cost can also be offset, over 10 years I break even on cost versus no pw; 12 years with no off-peak offset. PW cost + solar panels cost after incentives is $22,964.09. I use Samsung DVM eco system for HVAC and electric induction range, so heavy on the kWhs, light on gas.
If, instead, usage is 900 kWh/month, it would take 17 years to break even with no off peak offset.
In any case, my point is "cost justify" can include merely not losing money as an expression of user preference with a bonus of backup power. Saving money is not the only issue. Each situation is different and requires its own analysis, but powerwall should not be dismissed just because it might not save money.
Chancellor32
Member
Here in AZ one of the utilities is giving a $3600 rebate on a Powerwall. Take that with 30% tax credit makes it a no brainer to get it. Practically free.
BlueOvalFan
Member
I’ve never heard this before. Can you explain how this works, and the calculations for the rebate...?
SGIP Step 1 is long gone. Most are Step 3, 4 now and Tesla doesn't have any quota anymore
The SGIP (Self Generation Incentive Program) has 5 steps. This is the rebate amount per step for Small Residential Storage:
Step 1: $0.50/Wh
Step 2: $0.40/Wh
Step 3: $0.35/Wh
Step 4: $0.30/Wh
Step 5: $0.25/Wh
There is more to the calculation than that, but I don't remember the details. You can find all the information about the program here:
SGIP |
Not sure if this is a valid statement of practical free, but the $3600 does help a lot with the $21k cost of installation of 2 powerwalls. As for the tax credit we shall see if I can reach the new write off threshold this year to take advantage of that credit.
The ROI is still much longer than I would like, however, that is just one of the factors of why I'm installing batteries.
hodad66
Member
Here in central Florida I can't say that we have many outages BUTT!!! We had
two hurricanes in two years both with multiple days without electricity. To come home
(from evacuation) and find the food still cold and to be able to run the ceiling fans will
be priceless. That said, I would love to go another decade without a direct hurricane hit.....
Chancellor32
Member
Agreed the ROI on my solar was extended by about 5 years because of the battery. Tesla doesn’t install demand managers so the battery was a must have. I must say if I wasn’t getting the $3600 rebate it would be hard to justify the cost though.
I'm in Seattle and since my utility does net metering (no need to configure the battery for night use), we do not have time of day pricing (no need to do use shifting), and the WA state production incentive applies whether you have a battery or not the scenario for me was 100% for backup power.
I compared and contrasted a home standby generator and solar + a Powerwall. My test was to have a <10 year payback on the solar and price competitiveness with a home standby generator after credits and incentives. We don't have a ton of outages here however we do get yearly wind and ice storms which cause outages and of course there is the always present earthquake risk in the pacific northwest. Powerwall was the winner and I'm quite happy we went through with it (and likely will be SUPER happy during the next outage).
Cost - Powerwall: The quotes I got for the installation and delivery of a generator were higher than the Powerwall even before the federal tax credit. Natural gas is cheap but running your whole house on it is expensive, the Powerwall is essentially utility power prices. Generator maintenance is an ongoing cost, Powerwall costs zero. Both add value to the resale value of a home but I did not dig too deep in to how much they actually return on a sale.
Maintenance - Powerwall: After a home standby generator is installed it needs regular exercise, service, and maintenance (oil, battery, spark plugs). The Powerwall is virtually maintenance free. My time is valuable.
Capacity - Generator: For our home one Powerwall would not support the AC, oven, or dryer. Two Powerwalls could but with those high amp loads they would not last long and adding more changes the cost analysis to the generator. A generator could support all of those without issue. Our home consumes about 25kwh/day if we go about our normal business so a 14kwh Powerwall would last us about half a day with no sun and of course with sufficient solar production from our 8.5kw system it would last "forever". (note too that we consume almost nothing at night so on sunny days the Powerwall will charge for night time and the solar would power the home)
Convenience - Powerwall: If utility power is lost the only way you know with the Powerwall is that the lights blip for a quarter second. A generator takes time to spin up, get to speed, and switch over. Generators are loud, noisy, and produce exhaust. You can't even tell the Powerwall is there when it's in use. This is a big piece of mind for me that we don't have to mess with it in an outage.
Practicality - Tie: Our most common grid outages in this region (Seattle) are weather related. In a snow, ice, or wind storm you can be pretty much guaranteed that solar production will be near zero for at least during the storm which really limits the utility of the Powerwall. During an outage like this we could reduce our consumption to the minimum and extend the Powerwall out to about two days or so. Clearly with it's whole house capacity the generator is the winner. However in the event of an earthquake however a standby generator will likely be unusable if the natural gas supply is disrupted. Since earthquakes don't care about weather there is a good chance that if one happened it would be during a time that we get at least some sun. Though heaven help us if the big one hits during a 2 foot snowpocolypse...
X-Factors - Powerwall: The Powerwall is a sexy piece of house candy. Paired with solar it means that we can be almost 100% grid independent for electricity. That's a really good feeling that is hard to quantify. The app is really nice for monitoring the entire system (way better than my solar gateway) and if we ever get a Tesla car there is good potential for V2G or other home integration goodness.
I compared and contrasted a home standby generator and solar + a Powerwall. My test was to have a <10 year payback on the solar and price competitiveness with a home standby generator after credits and incentives. We don't have a ton of outages here however we do get yearly wind and ice storms which cause outages and of course there is the always present earthquake risk in the pacific northwest. Powerwall was the winner and I'm quite happy we went through with it (and likely will be SUPER happy during the next outage).
Cost - Powerwall: The quotes I got for the installation and delivery of a generator were higher than the Powerwall even before the federal tax credit. Natural gas is cheap but running your whole house on it is expensive, the Powerwall is essentially utility power prices. Generator maintenance is an ongoing cost, Powerwall costs zero. Both add value to the resale value of a home but I did not dig too deep in to how much they actually return on a sale.
Maintenance - Powerwall: After a home standby generator is installed it needs regular exercise, service, and maintenance (oil, battery, spark plugs). The Powerwall is virtually maintenance free. My time is valuable.
Capacity - Generator: For our home one Powerwall would not support the AC, oven, or dryer. Two Powerwalls could but with those high amp loads they would not last long and adding more changes the cost analysis to the generator. A generator could support all of those without issue. Our home consumes about 25kwh/day if we go about our normal business so a 14kwh Powerwall would last us about half a day with no sun and of course with sufficient solar production from our 8.5kw system it would last "forever". (note too that we consume almost nothing at night so on sunny days the Powerwall will charge for night time and the solar would power the home)
Convenience - Powerwall: If utility power is lost the only way you know with the Powerwall is that the lights blip for a quarter second. A generator takes time to spin up, get to speed, and switch over. Generators are loud, noisy, and produce exhaust. You can't even tell the Powerwall is there when it's in use. This is a big piece of mind for me that we don't have to mess with it in an outage.
Practicality - Tie: Our most common grid outages in this region (Seattle) are weather related. In a snow, ice, or wind storm you can be pretty much guaranteed that solar production will be near zero for at least during the storm which really limits the utility of the Powerwall. During an outage like this we could reduce our consumption to the minimum and extend the Powerwall out to about two days or so. Clearly with it's whole house capacity the generator is the winner. However in the event of an earthquake however a standby generator will likely be unusable if the natural gas supply is disrupted. Since earthquakes don't care about weather there is a good chance that if one happened it would be during a time that we get at least some sun. Though heaven help us if the big one hits during a 2 foot snowpocolypse...
X-Factors - Powerwall: The Powerwall is a sexy piece of house candy. Paired with solar it means that we can be almost 100% grid independent for electricity. That's a really good feeling that is hard to quantify. The app is really nice for monitoring the entire system (way better than my solar gateway) and if we ever get a Tesla car there is good potential for V2G or other home integration goodness.
