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We have an enphase system with a solar array that's a bit under 10x that size. We paid about $60k (ignoring tax credit) in the bay area, and I think we overpaid.

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.

You get about 6 hours of direct sunlight on the panels so his sizing is probably about right?

My dad gets about 6 kWh daily during the summer from an 1140 Wp PV array. 45° latitude, 1250 W/m² yearly insolation.

I didn’t get the battery but paid 28.5K (without rebates) for a 12.8kW array. I think that’s very reasonable. Heating, cooling and car charging are covered with around 6mWH capacity left a year. Thinking of converting my water heater now.

I like our Ruud/Rheem hybrid heat pump water heater. (The two brands are the same company. The only difference is whether you pay someone to install it.)

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.

Sounds wrong, check this out: https://www.youtube.com/watch?v=QWJpafOHoD0

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.

That’s insanely cost prohibitive, tbh. No wonder more people aren’t jumping at the opportunity. You would need 14 years just to pay back the cost of installation, and that’s assuming zero maintenance simultaneous with magically sustained like-new performance.

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.

The batteries are often rated for 20 years, after which you're down to 80% capacity, they don't simply stop working. Solar panels are rated for 30 years. So yeah, pretty hands off.

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.

I’ve never understood the calculations people make to justify that solar roof panels save them money.

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.

If everyone does that, all your stock won’t be worse much when the world will be either at war or starving. People have kinda forgot to think long term clearly. Also, you must live in a country where the politics are very anti climate. In my country it’s a good investment to install solar power.

It shouldn’t cost you more than $2/Watt. Obviously if you only do 5 panels, you still have all of the interconnect cost and it’s not nearly as efficient.

$2/watt has been way below average for a long time in CA, especially with a battery.

I read the national average recently spiked up to $3.10, thanks to the Biden administration's mishandling of Trump's China Tariffs.

> The quote for the solar kit that could produce ~1.5kW (2170W Solar Kit: 7xURE NSP 310W - Mono 60 Cell - All Black Panels + 7xEnphase IQ7 60-Cell Microinverters w/QCables + 1x Enphase IQ Combiner 3 + Wireless Monitoring) was $6.5k.

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.

The enphase batteries are stackable to get more amperage. However, we were definitely amperage limited when we sized ours. We have a few high amp / low duty cycle devices.

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...)