Justifying powerwall cost

[Merrill]

Maybe someone out there can help me with cost justification on installing 2 Powerwalls. The quotes I’m getting are between $23,000 and $25,000 before FTC and SGIP. I’m retired so the tax credit is not that useful and step 4 on the SGIP is around $7,000, so a net of just over $18,000. Since I’m not sure how many times and for how long the power will be out it seems like a lot of money just for backup. If I could save some money on my PG&E bill it might make sense, I have solar and I’m with our local CCA. What works for me right now is my peak kW is from 1 to 7 and the credits I get back from high solar generation at that time make my system work. Not sure if I could save money with the addition of Powerwalls.

 

[cwied]

I don't think it's enough to make the difference, but with Powerwalls you could export all your solar production during peak if you get enough sun before 1pm to charge them up enough for that. The effect would be that you would net the difference between your 1pm-7pm rates and your sunrise-1pm rates for the amount that you use between 1pm-7pm (minus 10-20% for battery losses).

I think for a pure backup solution, a generator is generally more cost effective.

On the FTC: I believe you can carry over the unused portion of the FTC, so if you ever pay taxes, you can use it. You can also use the credit by converting regular IRA's to Roth if you have any of those.

 

[woferry]

Honestly, I don't get the impression a Powerwall ever pays for itself in terms of cost of energy, at least for most common rate schedules, perhaps unless you get a big SGIP benefit. Sure, you can play tricks to bank energy that was worth less and draw from the PW when the energy costs more, but there's efficiency losses with storing and drawing that energy that take away from some (if not most or all) of those gains. Personally I find more value in the PW as a whole-house backup, in the event of grid outages, etc., which seem like they're only going to get worse in our area. And perhaps the value increases in the future as rates continue to change (TOU peak hours shift later, etc), though of course they don't last as long as the panels should either, so it's tougher to consider the PW a long-term play. So sure, you might save some money on your PG&E bill, but I sincerely doubt it would ever come close to the cost of the PW.

 

[SoundDaTrumpet]

With $18k net that’s $1800 per year over the warranty. Overwhelming majority cannot cost justify. You’d have to have a unicorn installation price from times past, have a undersized solar with a sizable annual true-up, and 100% ready to go electrical panel to go with it. Even so with stars aligned, ROI is 5-6 years here (Step 2, Tesla install, $600 annual true-up, and friendly MLO panel). This is very rare. For the 97% majority adding more solar panels is more cost effective if one’s solar is undersized than adding a Powerwall. Ever wonder why Step 1 vanished in a snap and SGIP uptake is slowed so much? People have done their numbers.

 

[Merrill]

With $18k net that’s $1800 per year over the warranty. Overwhelming majority cannot cost justify. You’d have to have a unicorn installation price from times past, have a undersized solar with a sizable annual true-up, and 100% ready to go electrical panel to go with it. Even so with stars aligned, ROI is 5 years here (Step 2, Tesla install, $600 annual true-up, and friendly MLO panel). This is very rare. For the 97% majority adding more solar panels is more cost effective if one’s solar is undersized than adding a Powerwall.

Wish I could add more panels but I’m maxed out, no more room on the roof and no where to do a ground mount system.

 

[Kant.Ing]

If you already have solar, the dollar benefit from adding Powerwall would be less, than without solar, since you can only charge Powerwalls from solar. Still, the overall benefit all depends on your usage, specs, and goals.

Assuming a TOU rate, and your solar can fully charge your 2 Powerwalls during partial-peak hours (morning) and your household consume 25kWh during on-peak hours (afternoon to evening), the benefit is 25*(on - part). In summer, it is 25*(.49-.27)=$5.50/day, and in winter this saves about $3.25/day. Assuming same amount days of winter and summer in a year, and let's forget about weekend schedule, the annual saving is about $1,600. Just a ballpark and YMMV.

IMHO, having a power backup system that is able to silently replenish itself on a daily basis gives us the most sense of security and peace of mind.

 

[SoundDaTrumpet]

Wish I could add more panels but I’m maxed out, no more room on the roof and no where to do a ground mount system.

Hmm... I have to assume your panels output decent power. I have found out that vent pipes can be relocated and the firemen vent setbacks tend to be too conservative. For example at a hip only one side needs the 3ft clearance. It would be good idea to contact your solar installer. I was surprised to learn this from Tesla when I asked if they can add panels for me. Short answer is no must be six (6) panels minimum.

 

[Merrill]

Hmm... I have to assume your panels output decent power. I have found out that vent pipes can be relocated and the firemen vent setbacks tend to be too conservative. For example at a hip only one side needs the 3ft clearance. It would be good idea to contact your solar installer. I was surprised to learn this from Tesla when I asked if they can add panels for me. Short answer is no must be six (6) panels minimum.

Yes, 18 panels are older installed in 2010 the problem in replacing those panels for current more efficient panels is that the inverter would have to be replaced as well. Venting is not the problem just no room.

 

[Dan123]

Your PW installation seems a bit more expensive than it should be. Are there any unique electrical issues? The PWs themselves are $6700 and the gateway is $1100. $10000 for installation seems like a lot.

If you start comparing the cost of 2 PWs with the cost of a full-house generator, the PWs are competitive. When they are $15000 (and $10,000 after tax credit). That assumes that you want to have a full-house backup in the first place.

 

[Vines]

Powerwalls don't generally make financial sense if looking for pure payback. Its often as long as the warranty or nearly. Only Tesla has the magic $6700 price, other installers buy them at the same price so mark them up a bit to keep the lights on.

However more efficient solar panels and the new rooftop setback rules can likely increase the PV system size.

Not many people realize that the fire rules were relaxed middle of last year, so this provides some opportunity for more panels perhaps. Also today's 370 watt and larger panels have a great watt density. There is no longer any requirement to setback at hips and valleys. The 36" ridge clearance is reduced to 18" on either side of the ridge for houses with under 33% of total roof area populated with solar.

 

[Merrill]

Your PW installation seems a bit more expensive than it should be. Are there any unique electrical issues? The PWs themselves are $6700 and the gateway is $1100. $10000 for installation seems like a lot.

If you start comparing the cost of 2 PWs with the cost of a full-house generator, the PWs are competitive. When they are $15000 (and $10,000 after tax credit). That assumes that you want to have a full-house backup in the first place.

Yes, it does seem expensive but the 2 quotes were very similar no special issues in fact the powerwall would be 4 feet from the main panel. I’m waiting on a quote from Tesla doubt it will be any cheaper.

 

[SoundDaTrumpet]

Not many people realize that the fire rules were relaxed middle of last year, so this provides some opportunity for more panels perhaps. Also today's 370 watt and larger panels have a great watt density. There is no longer any requirement to setback at hips and valleys. The 36" ridge clearance is reduced to 18" on either side of the ridge for houses with under 33% of total roof area populated with solar.

Great info!

 

[Vines]

Here's the relevant text regarding pathways. Its a lot better when designing on difficult roofs.

 

[SoundDaTrumpet]

Yes, it does seem expensive but the 2 quotes were very similar no special issues in fact the powerwall would be 4 feet from the main panel. I’m waiting on a quote from Tesla doubt it will be any cheaper.

Tesla was very transparent with the main panel upgrade. They sent me the bid from the 3rd party to substantiate the uptick in prices.

 

[miimura]

Here's how my 2 Powerwall system penciled out.
Total system cost: $20,318
SGIP Step 1 Rebate: $11,600
ITC Tax Credit: $2,615
Net Cost: $6,103

I had pre-plumbed and pre-wired for a natural gas backup generator when I had the house built 6 years ago, but never permitted and installed the generator. I had budgeted $3,500 to complete it. So, any payback on the Powerwall system would be based on roughly $2,600 not counting savings from operation and maintenance or fuel for the generator.

Since my solar is small relative to my total usage, I can actually use the Powerwalls to reduce my payments to PG&E. Before Powerwalls, I was paying about $1,000 per year at true-up. By shifting an average of 10kWh/day out of Peak rates during the Summer season and about 5kWh/day during the Winter season and charging the Powerwalls from Part-Peak solar generation, I estimate that I might save $625 per year. That is a 4.2 year payback. In reality, it might be closer to $500/year, so that would be 5.2 years payback.

I don't think I could get this short payback installing the system today. If I was making the decision today, I would probably wait to see what the next round of the SGIP program looks like.

 

[Shygar]

Yes, 18 panels are older installed in 2010 the problem in replacing those panels for current more efficient panels is that the inverter would have to be replaced as well. Venting is not the problem just no room.

I thought inverters last about 10 years anyways right?

 

[Merrill]

Here's how my 2 Powerwall system penciled out.
Total system cost: $20,318
SGIP Step 1 Rebate: $11,600
ITC Tax Credit: $2,615
Net Cost: $6,103

I had pre-plumbed and pre-wired for a natural gas backup generator when I had the house built 6 years ago, but never permitted and installed the generator. I had budgeted $3,500 to complete it. So, any payback on the Powerwall system would be based on roughly $2,600 not counting savings from operation and maintenance or fuel for the generator.

Since my solar is small relative to my total usage, I can actually use the Powerwalls to reduce my payments to PG&E. Before Powerwalls, I was paying about $1,000 per year at true-up. By shifting an average of 10kWh/day out of Peak rates during the Summer season and about 5kWh/day during the Winter season and charging the Powerwalls from Part-Peak solar generation, I estimate that I might save $625 per year. That is a 4.2 year payback. In reality, it might be closer to $500/year, so that would be 5.2 years payback.

I don't think I could get this short payback installing the system today. If I was making the decision today, I would probably wait to see what the next round of the SGIP program looks like.

I thought that the legislature approved another 800,000,000 in SGIP last August.

 

[miimura]

I thought that the legislature approved another 800,000,000 in SGIP last August.

Funding has been approved. However, I think the existing program has to run its course first. I assume they will hold workshops and revise the program before they start allocating the new funds.

 

[Merrill]

Funding has been approved. However, I think the existing program has to run its course first. I assume they will hold workshops and revise the program before they start allocating the new funds.

I wonder when this will happen.

 

[Late2theGame]

Yes, it does seem expensive but the 2 quotes were very similar no special issues in fact the powerwall would be 4 feet from the main panel. I’m waiting on a quote from Tesla doubt it will be any cheaper.

I used TESLA to install additional solar panels and 2 Powerwalls in my garage within ~5 feet of old main panel and old solar inverter.
The Powerwall part was about $18,000 prior to any rebates. This was beginning of this year.