Do you mean 15kw? 1.5 is only like 4 panels, it wouldn’t make $400 per month and wouldn’t cost anywhere near $25k.
But, I was also considering having a 10kW battery to store that energy and to have a backup power, like Tesla Powerwall - $10k. And then there was work to install, permits, my time. Overall my estimate was, realistically it'd be ~$25k. Maybe I was wrong.
On my house I have two sections of roof that are flat/horizontal. Roof is pretty thin there and although there is insulation, on hot days ceiling was getting worm in the 2 rooms under these sections. I also was hoping that an extra layer of solar would insulate my roof a bit more. So I wouldn't have to run AC that much. So the hope was to stop wasting annoying $400 on AC in the hottest months. But the cost of installing solar felt prohibitive. So I've made a quick calculation and spent $100 on the reflective roof paint instead...
5kWh battery thing for $1,500: https://signaturesolar.com/eg4-lifepower4-lithium-battery-48...
Growatt 3kW Stackable Off-Grid Inverter for $700: https://signaturesolar.com/growatt-48v-3kw-150vdc-stackable-...
Solar panels are $2-$3 per watt depending where you live. 4x300watt panels is just the ticket, depending where you are and whether you can get a 30% tax credit that's about $2000.
Whole thing all together would be about $5000. It would generate about $1 of electricity a day. Would eventually pay for itself over its lifetime if you don't mind faffing about with it to get started.
> On my house I have two sections of roof that are flat/horizontal. Roof is pretty thin there and although there is insulation, on hot days ceiling was getting worm in the 2 rooms under these sections. I also was hoping that an extra layer of solar would insulate my roof a bit more.
It will be slightly cooler underneath it.
After those 14 years, you “make” an annual non-compounded 7% ROI (again in 2022 dollars).
Spending some of that money on insulation and sticking the rest in a savings account somewhere is a much wiser bet.
Every time I do the calculations, it’s money loss.
If you want to install them for environmental reasons, great. But don’t kid yourself that’s is a great investment. It’s not. Putting the money into an S&P 500 index fund for 14 years is a better investment. It will double about twice in that time.
As for why do it, well, a right sized system allows you to be independent from the utility company so if monthly financing for it falls to the same ball park you're paying for electricity already you've simply locked in a rate and hedged against further price hikes.
If I was paying on average $99/mo to PG&E or whomever I'd eyeball a $12,000 system financed over 10 years. That would get you about 20kWh storage and enough panels to keep it full which may or may not be enough for your house.
That crossover point obviously varies from house to house and what's available to you locally. I think it makes a lot of sense for new houses, that way they might avoid a potentially very costly hookup to the grid which in some locations is tens of thousands of dollars in itself.
Remember to take 23% off for the federal tax credit.
> But, I was also considering having a 10kW battery to store that energy and to have a backup power, like Tesla Powerwall - $10k.
That's a not-so-small detail, accounting for $18.5k of the bid! A battery is also pretty unhelpful for reducing the A/C portion of your electric bill, especially since most traditional A/Cs require more than the 20A that the Enphase 10kWh battery can output and will pretty quickly drain any home backup battery that could support that current demand.
> So I've made a quick calculation and spent $100 on the reflective roof paint instead...
$100 in reflective roof paint, while a great measure to take, isn't going to reduce A/C electricity usage more than PV, which has the added benefit of offsetting your other electricity usage when you are not in the cooling season.
It can definitely run our 60+ amp HVAC system, but not overnight. (We didn't buy it for that, but it's nice that we don't even notice our frequent, short outages until enphase and pg&e email us...)
I read the national average recently spiked up to $3.10, thanks to the Biden administration's mishandling of Trump's China Tariffs.
We have about 2.5 watt hours of battery per watt of solar panel, which seems about right around here. (The battery is fully charged by the end of day about 95% of the time.)
Your quote has 6.6 Wh/W, and the PV bit is small, so fixed costs are also biting you.
Edit: we have electric heat, and you probably don't. Our worst case days are cold and cloudy, so perhaps the battery sizing makes sense, though if you want AC at night, you'll want enough solar panels to charge the battery and run the AC.
However, it was not trouble free:
The time of day scheduling feature is useless. Once or twice a month it gets stuck in "lower temp" mode. The app reports kWh used and displays alerts, which is nice. Otherwise, there's no reason to give it WiFi access.
Pay for the leak detector option. It's relatively cheap, but not included for some reason.
You're likely to have condensation issues unless you use a good installer, or do it yourself and follow directions.
The power lead on ours wore through due to vibration too, so pick someone that's experienced/conscientious enough to route wires carefully.
My dad gets about 6 kWh daily during the summer from an 1140 Wp PV array. 45° latitude, 1250 W/m² yearly insolation.