It's possible, I think to do smaller installations, like this guys solar pool assembly.
He has three or four panels, a couple inverters and a two or three phase pump.
I'll probably build one like this next year at my house since I need to replace my pump soon.
Pools in particular can benefit from something like this since the ideal time to filter is when the sun is direct
I'm going to experiment this winter with a solar collector and one or two panels to see what kind of performance I get on moderate days. The idea is to build a small waterfall, with a pond pump pushing water through and letting it flow back into the pool. I don't expect it to recreate Niagara, but hopefully it'll be functional. If it is I might add a heat collector and run it to that via a splitter valve.
In my case I'm not looking for ultimate efficiency, but just a way to isolate and reduce the overall impact on my bills while maintaining the same standard of living. Will it pay for itself? The math says yes, but we'll see how empirical evidence plays out.
Amusingly, I've got a plug in hybrid, so my electric usage just shot up by 14kwh a night. THAT however, is easily paying for itself in reduced fuel cost.