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Solar is currently only viable if excess energy is stored as heat.

One of the few installations I have seen which actually paid for themselves were down in PR where my SIL has a 2nd home and they have a solar hot water heater.

Even with guests and the occasional cloudy day, there is ample hot water reserve.

Storing the excess as electricity is another matter though and so far a nice toy.

Solar is currently only viable if excess energy is stored as heat.

One of the few installations I have seen which actually paid for themselves were down in PR where my SIL has a 2nd home and they have a solar hot water heater.

Even with guests and the occasional cloudy day, there is ample hot water reserve.

I also created my own solar hot water system using glassed in boxes with copper tubing. I got the copper years ago, when it wasn't as pricey as it is now. I used a 2500 gallon septic tank(unused) which I insulated with spray on insulation as a heat reservoir. I think the whole system cost me about 2 - 3k. I get year round hot water and heat from it. I live in NH, in the white mountains, so saying I get all my heat from it, is saying something significant. My house has radiant hot water heating. The water pump is powered by a couple of solar panels and some Marine deep cycle batteries, from Walmart. I'd estimate it saves me nearly 1500 per year, but as costs continue to climb, and my only costs are batteries every few years and a pump every 10. It has been in continuous operation for 18 years. The septic tank reservoir maintains a nearly consistent 135 degree temperature, though I could crank it higher by adding panels, it has proven to be just about right. My hot water temperature is around 130 degrees and my radiant floor closed loop is around 105 degrees.

The heating cycle is turned on when the sun is shining, and only pumps water to the panels if the water can gain something. I have temperature sensors at the beginning and end of the loop, and if the water is equal or gaining temperature, I continue the circulation, if not, it shuts off. It has a timer to shut it down at night, which I occasionally have to adjust for seasons. When it snows, I run the warm water through the system to melt the snow off, using a manual override on the pumping system.