Small Solar Array. Large Energy Demand

[Blup85]

Background:
I've got a vacation home that is used very heavily in the summer, with huge loads averaging 60-80Kwhrs a day sometimes for about 3 to 4 months.
I installed my own 7kw solar array, but due to the shading and direction of the house it has the power output of about a 3kw array. I'm ok with it because I did it myself, and it was relatively cheap all things considered.
Due to the political climate in northern Ca and PGE for fires, I'm fully expecting PGE to shut power due to "wind danger" or if a bear passes wind in the forest, so I placed a powerwall 2 order a week ago. ( Two units)
My concerns for people in the know.
1. Due to my small solar but large demands, wont my powerwall be always empty, thus never hedging peak demand?
2. Is there a program where I can charge at night and not take the SPIG credit? My summer Bill's are ridiculous, so hedging peak rates might actually make sense.
3. What price am I going to see for a 2 powerwall system?
My install can't be any easier, they would be placed 5 ft from my main 200 amp panel. I don't like being taken advantage of ( thus doing my own solar)
4. This isn't that complicated. how do I do this myself?
5. What's my other options?
Thanks!

 

[miimura]

If it's a vacation home that has grid tied solar and net metering, why does it matter how much your bills are during the Summer? I would imagine that the vacant time would accumulate credits for you quite nicely. I would think that the annual true-up could be quite low.

Also, for a vacation home, I would not spend the money on Powerwalls. If you have a natural gas hookup or a particularly large propane tank, I would just get a backup generator. 16-20kW generator would be about half the cost of 2 Powerwalls after tax credit. It only needs to be enabled when you're there.

 

[dotbombjoe]

That's a lot of power. What is going on to pull that much power -- AC? I'd say the safest bet would be spending money to reduce your consumption...more efficient appliances and the like.

I agree with miimura, I suspect a gas generator would likely be more cost effective if that is an option. My understanding is you will not get any tax credits or qualify for SGIP rebates if you aren't charging primarily (exclusively?) from solar and your array won't be produce anywhere near enough to charge the batteries much on a daily basis.

Other recent posts suggest you are looking at $18-25k for two powerwalls installed.

 

[Blup85]

That's a lot of power. What is going on to pull that much power -- AC? I'd say the safest bet would be spending money to reduce your consumption...more efficient appliances and the like.

I agree with miimura, I suspect a gas generator would likely be more cost effective if that is an option. My understanding is you will not get any tax credits or qualify for SGIP rebates if you aren't charging primarily (exclusively?) from solar and your array won't be produce anywhere near enough to charge the batteries much on a daily basis.

Other recent posts suggest you are looking at $18-25k for two powerwalls installed.

I should add we use the house a lot even in winter.
My big loads are a spa, 3 convection wall heaters ( winter) and 3 refrigerators, two water heaters. Until last fall I had 3 water heaters. 60gal and 100 gallon for main house and 40 gallon for guest house.
I've gone to a hybrid setup for the main house keeping the 60 gallon on a time of day plan ( cheap electric) and running instantaneos gas during peak hours.
I'm on an EV rate, so my usage is pretty high but mostly part peak and off peak.

I recieved a quote from Swell energy for about 25k for two powerwalls and with rebates it comes out to ~11k net. Ouch..I just dont see the level of effort matching the cost of install. Install looks easier than a solar install, but we just cant buy the parts so they have us by the shorthairs.


Ill try some local energy companies around here, but I'm in a pretty rural area so our contractors are typically not on the leading edge of technology.

 

[dotbombjoe]

I'm not sure whether they'll configure powerwalls to charge from the grid -- they certainly do in other countries, just not entirely sure they do it here. If they do, you definitely won't qualify for the SGIP rebate, which means you're looking at more like a $17+k investment. Hard to see how those numbers make much sense.

If your concern is providing backup, then perhaps it is worth the investment but that's a mighty expensive backup plan and you'd really have to ration your usage during outages. It could easily keep the fridges and water heaters but the spa and space heaters will chew through it pretty fast...and since you don't generate much, any extended outage and you'd be struggling to keep things going.

I'd assume the spa and heaters are the big draws. Fridge's shouldn't take much unless they are old., in which case you should replace them with new appliances. How about those water heaters...are they as efficient as you can find? Replacing them with tankless designs could reduce their demand by 20-30% depending on usage.

Is gas (propane) not an option?

It looks like most of your usage could be converted to gas: spa, convection heaters, water heaters...all great candidates for gas appliances. And it can also feed a generator to power your house during outages.

Might make sense to have someone look at your solar as well. Maybe there is a way to improve the performance...trim trees, relocate some panels? Shading can devastate performance depending upon your equipment/setup so if shading is an issue, you may want to do more research to make sure your setup is optimized to deal with your shading challenges.

Reducing consumption is always the best option you have in my opinion.

 

[cwied]

I'm not sure whether they'll configure powerwalls to charge from the grid -- they certainly do in other countries, just not entirely sure they do it here. If they do, you definitely won't qualify for the SGIP rebate, which means you're looking at more like a $17+k investment. Hard to see how those numbers make much sense.

Actually Powerwalls that charge from the grid are still eligible for SGIP. You can get SGIP without solar. It's the federal Investment Tax Credit that doesn't allow grid charging. Your main point is still valid, though.

 

[dotbombjoe]

Actually Powerwalls that charge from the grid are still eligible for SGIP. You can get SGIP without solar. It's the federal Investment Tax Credit that doesn't allow grid charging. Your main point is still valid, though.

Thanks for the correction!

Also, if I recall there is some threshold involved I think too, right? As in, you have to charge at least x% from solar to qualify. Ok, yeah, I just looked it up again, must charge at least 75% from solar. I don't know if that matters though as I'm not sure it is possible to configure the powerwall to optimize for that scenario. If it could be optimized, I'd think that could help the OP a lot in their particular circumstance.

SCRATCH THAT...apparently the ITC is reduced based on the %age your system is charged by PV. So, if your system is only charged 80% by PV, then you only get 80% of the credit.

 

[miimura]

Thanks for the correction!

Also, if I recall there is some threshold involved I think too, right? As in, you have to charge at least x% from solar to qualify. Ok, yeah, I just looked it up again, must charge at least 75% from solar. I don't know if that matters though as I'm not sure it is possible to configure the powerwall to optimize for that scenario. If it could be optimized, I'd think that could help the OP a lot in their particular circumstance.

SCRATCH THAT...apparently the ITC is reduced based on the %age your system is charged by PV. So, if your system is only charged 80% by PV, then you only get 80% of the credit.

That is for commercial. If you are residential it is 100% charged by renewable or no ITC for you.