[bruce511]

I'm in the same camp as you. I'll add that my panels are returning 16% on capital spent, and it's going up as electricity prices go up.

So, yes, I could probably get a higher return if I invested that capital elsewhere, but, apart from the diversification, I get benefits beyond the raw financial return.

Firstly, earlier this year, we had a cable coming into the house fail. By the time the electrician and city had done all they needed to do to sort it out, almost 4 days had passed. We would have been without power for that time. As it happens we ran completely on solar for that period - freezers stayed frozen, could run the laundry, etc. Some stuff was limited (no oven, no hot water) but the impact was minimal compared to what it might have been.

Secondly, during the day at least, I'm not really fussed about electricity usage. If lights are on, or AC is on or whatever. So there's less "hey, that light is costing money" etc. So we end up using more electricity, but the marginal cost (during the day) is 0. My next car is electric (already on order) and that can charge at home as well (during the day, I work from home) and so that just increases the return (utilization of available power goes up.)

From a financial point of view, for me, it's a no-brainer. Obviously ymmv - everyone's numbers are different. For me the payback is in the 5-6 year range (probably under 5 once the car comes online.)

[jonhohle]

In an average year (not the past 4), 16% would be amazing. That it’s effectively guaranteed and will almost certainly increase every year is icing on the cake. I’d take that trade any day.

[throwaway2037]

    > my panels are returning 16% on capital spent

Can you share your calculations?

[mschuster91]

Not OP but I'll run what I plan on doing. In Germany you can get a plug-in ready kit with 2.2 kWh battery and 920W panels for less than 600€ [1]. The panels are about 1.8 m² each (=3.6 m² total), so with on average 1.200 kWh/m² solar radiation and 25% efficiency I'm looking at up to 1080 kWh in energy I'll get out of the system per year.

Electricity here in Germany is expensive at an average 30 ct/kWh, so the panels save 324€ worth of electricity - an ROI of > 50%. Choose some better quality for the inverter and battery and you'll still be north of 30% ROI.

The key thing making this high ROI possible is that it's small. Counterintuitive, yes - but explained by the fact that for larger installations than that, setup costs go up: you need to install the panels on your roof instead of hanging them off your balcony which can be thousands of € in labor, you need to run new power wires...

[1] https://www.idealo.de/preisvergleich/OffersOfProduct/2092828...

[2] https://www.swm.de/unternehmen/magazin/energie/pv-ertrag-im-...

[bruce511]

Your numbers are likely off by about half (in Germany your sunlight is less than 1200w/m2, panels are more like 22% effecient, you'll gave at least some cloudy days, your panels won't be tracking the sun.)

But a small system is still going to bring a return and is cheap to install. And it'll give you a real way to understand the concept and to experiment.

I started with a 660w small system, and it gave me lots of insight for planning my current system.

[cjrp]

Are these the kind you could DIY-install on a balcony for example?

[mschuster91]

Yes, precisely.

[bruce511]

The inverter keeps a log of electricity generated, used, battery used, imported and so on.

I put that in a spreadsheet which calculates money saved. (Which is reasonably complex because of pricing tiers although fortunately I don't have to deal with daily pricing changes.)

Then some math returns the return on investment per month and per year.

[throwaway2037]

Do you also subject the cost of upfront capital? Example: Imagine that you didn't have the upfront captial, and you needed to borrow it "from a bank" at X% for Y months.