Solar panels generate DC voltage. (at low current low voltage levels.) It is great for some applications. NOT powerful applications.
If solar panels are used to generate AC it must be done through an inverter of some type. Many are 50% efficient, and all of them produce Square Wave (not Sine Wave) AC. Sine wave AC is very noisy and generates some heating in the transformers.
I bought my first solar panels in the 1980’s. They were surplus out of Los Alamos.
Need to brush up on the current state of solar panels and especially inverters if what you posted was from the 1980’s.
Square wave inverters produce noise, making them unsuitable for motor and many electronic applications. Pure Sine Wave inverters are not noisy and efficiency is much greater now.
There are plenty of great sine wave inverters and the efficiency are over 90%. Take a look at the Tesla Power Wall for an example of state of the art available today.
Pretty much what I said. Not good for large applications.
Heat water? sure. Run an entire house completely? Nope.