My electric bill came yesterday... $460. I nearly wet my pants.
The thing that's really hurting everyone is that energy costs are so much higher. I actually used slightly less electricity this August than last, but my bill is over $100 higher.
Powering a tank with solar power individually is not practical for the reasons mentioned... cloudy days... no tank power. However, most solar packages do not work this way. They come with something called a "grid tie inverter." These are power inverters that work by accepting power from the solar panel and putting the power onto the electrical system of your home, simultaneously with the regular utility power.
This means that you do not need a system big enough to support your entire tank. The solar power produced contributes to the power supplied by the utility... so if your solar system can produce 2000w total, if your home's total electricity consumption is say... 3400w, then you are only pulling 1400w from the utility. If the sun goes behind a cloud, the solar output might be only 400w, and the utility provides the other 3000. It's all seamless. Really big systems can actually be arranged to sell power back to the utility... so if your solar system is 10,000w, and your home is drawing 3400, your electric meter starts to run backwards and you are actually selling 6600w back to the utility.
I've been running the numbers myself and even with the government paying for 50% of the systems, you are still looking at a 10+ year ROI, not including maintenance costs and what have you over the life of the system. IMO it's not terribly practical yet.