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My take on the solar argument for household use. I say this as a software engineer who's used to dissecting all major decisions, and as an investor who budgets heavily and invests to retire when my wife and I are in our 50's.

1) Very good for some climates and horrible for others. It's good for me cuz I live in Alabama where we average 5 hours per day of sunshine suitable for good solar absorption, more than that during the summer, and most of my power cost is from running the A/C during summer, not running the heater during the winter (even if I had electric heat). If I lived in the northeast, say in New York, I probably wouldn't give it a 2nd thought because most of my electric consumption would be for heat during the winter, when there's less sunlight in an area that already doesn't have as many hours per day of sunlight suitable for solar power.

2) It depends on if your power company does net metering, which is a fancy term for them paying you a suitable amount per kwh for extra power you put onto the grid for solar power you generate but don't use. (For example, if I had enough solar on my house to be self-sufficient for the summer I'd probably put a fair amount of power onto the grid during the spring and fall when the sunlight is good but the A/C use is down ("down" compared to Alabama summer days). The two main power companies in Alabama have different net metering rates. The one done by the TVA is good, but Alabama Power's net metering is practically non-existent (along with a monthly fee Alabama Power charges just to have your solar power on their grid). So research that. Your choice for solar may come down to your net metering rates/fees. If you have good net metering, you can convert to solar incrementally (i.e. a few solar panels and one inverter, with no battery storage) by staying tied to the grid to get power beyond what you're generating at the time. This allows you to kick the tires so to speak to see if it's affordable for you. If you have poor net metering (meaning you'd pay more for the privilege to stay on the grid than they pay you for the power you sell them), then going solar is an all or none decision where you either go all in and generate enough solar power and have enough battery backup and backup generator (think a week of rainy days in the winter) or don't spend a penny at all for solar.

3) Assume an 80% efficiency on the inverters converting DC power (coming from the solar panels) to AC power (to be used by the house and/or stored in a battery or two for nighttime and rainy days).

4) Now for Return on Investment (ROI). I make about 11.5% average return on my investments, so I'm hesitant to throw a lot of money up front for solar if that money can make me better money elsewhere. It'd take about 7 to 9 years for me to get back my up front costs if I went full solar (with some battery backup and a small diesel generator). However, that assumes power rates remain constant. If power rates go up by about 4% per year like they usually do, now it takes only 6 to 8 years to get my money back. Plus, I'd have the peace of mind in knowing that my future energy costs aren't dependent on the whims of someone else increasing the rates. Think of it as a small 4% annuity to have some stability in an investment portfolio that's otherwise mostly high growth. I had an electrical engineer review my research and confirm my numbers are pretty accurate.

All that being, when I retire and move to the last place my wife and I plan to live the rest of our lives, expect me to go all in on solar if I'm somewhere in the south. If we wound up staying in our 2-floor house that was big enough to raise 4 kids (all of whom are now grown and moved out, therefore we're liable sell and downsize in retirement, the only reason I haven't already invested in solar) it'd cost $30K to buy and install 35 400W solar panels (I have a large portion of my roof facing south), 1 inverter, 5 batteries (enough storage for a full day's worth of power use), and a diesel generator to be used maybe 5% of the time (automatically switched on by the inverter when it detects low battery storage). This is after the 30% tax credit. All of those parts have either a 10 year or 25 year warranty, but for realistic purposes the warranties are more like 8 years or 20 years, because the warranties allow for the parts to degrade some and still not be replaced if they're operating a little less efficient each year (especially the batteries). So halfway into the 10 year warranty of my 35 solar panels I can expect them to operate as though they're only 30 or so panels.

So if my wife and I decide to stay in our large family house for life, I'll take 30K out of our investments, go all in on solar, and put the $380 per month I usually spend on power and natural gas (but won't if we're 100% solar powered plus a little diesel fuel) back into investments. (In practical terms, that's $380 less per month I'd withdraw from investments to live on.) If we retire to a smaller house it'll have even less upfront costs.