I live in Northern CA, and in 2017 I decided to go solar. I bought a 4.1kW system (twelve 345W panels) for $16.5K (actual cost about $11K after tax breaks). Any power I don't use is fed to the grid, and at the end of the year the amount of grid power I've used vs. the amount I've sent to the grid is calculated to determine whether I have to pay or whether I get paid something (it's best to put into the grid exactly as much power as you use, since the amount PG&E pays for any overproduction is paltry). Regardless, there is a $10 per month service charge just to remain connected to the grid.
Although the system works fine, there is no way to know how much power you're producing vs. using until the end of the year. Also, if the grid power ever suffers an outage during the day, the solar system ceases to function (apparently it needs SOME grid power to access the solar production...which is strange and annoying).
So I looked into getting a battery system. The Tesla Powerwall 2 had recently come onto the market, and although it's expensive (around $12K fully installed), here in CA it came with a huge tax break and a rebate, reducing the cost to less than $5K. I was one of the first few hundred people in CA to order a Powerwall.
The battery holds a 13.5 kWh charge. To put that into perspective, that's enough energy to power my home for around 30 hours of normal use.
So the way this works is you set the Tesla phone app to the percentage you always want to remain in reserve for power outages. I've set mine to 25%, since outages are extremely rare and never for more than a few hours (FYI, in case of an outage, the switch to battery power is almost instantaneous and without any interruption). The remaining 75% is more flexible, and is used to power my home whenever there is insufficient or no solar power generation.
During the shortest day of the year, the battery uses a maximum of about 60% of its charge to get me through the darkest hours. It only gets better than that every other day of the year, weather permitting. As long as the sky isn't covered with dark clouds during the day (thin cloud cover is okay), there's enough solar power generated to refill the battery. That keeps me 99% free of grid power, although I'm still connected to the grid (for $10/month) for the times when it's too cloudy for too long or if I need to put more of a drain on the system than the battery can handle (that includes, unfortunately, most air conditioning systems if they need to run when there's insufficient solar power generation). I also need a grid connection to feed excess power to the grid (which should pay for that monthly fee, although we'll see once air conditioning season hits).
So for about $16K, I have a solar and battery system that should pay for itself within a decade or so (although it's hard to say for sure yet, since I don't have a full year on the system to properly calculate the costs). Your costs may vary, but it may be worth looking into such a system.
Attached are some pictures of the Tesla app (which is unexpectedly addicting, since you can see which appliances are using the most electricity by watching the usage in almost real time). The first pic shows the percentage of power available in the Powerwall, as well as whether it's charging, discharging or standing by. The second pic shows the power flowing from the solar to the house and the battery. The third pic shows the power flowing from the solar to the house, with excess power feeding to the grid (because the battery is full). The fourth pic shows the battery discharging to power the house at night. And the fifth pic shows how you can monitor the daily power dynamics for solar, house, battery and grid.
FYI, a TV, receiver, DVR, fridge and a few lights use about 0.3 kW (it varies somewhat). A microwave or a treadmill can add around 1 kW. Oddly enough, a computer with a couple monitors, a space heater or a hair dryer add almost nothing. I don't think I've ever used more than about 2.5 kW at a time, and I average about 10 kWh per day (that'll go up during A/C season).
I hope you find this info useful.
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