What is the point of a home solar or wind power system that has no self contained redundancy? It is little more than a "toy" or a conversation piece at time because it still relies on grid to feed it at times.
The point is that often it can drastically reduce your energy costs. Particularly during the high-demand summer days. It all depends on how much you pay per kWh, how much the grid will pay you for your surplus, how much you can generate and how much the installation costs.
I have known people who have installed solar electric systems where the breakeven point is less than 3 years.
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So why doesn't everybody do it?
1) Even with tax breaks and other incentives, you still need to invest serious $$$ in the system.
2) Some people's homes aren't good sites for it. Besides the need for a good view of the sky where the sun is, you need a good roof area, a place for the inverter, etc.
3) Some are waiting for the price to come down. Remember when VCRs were $1000?
4) In some areas electricity is so cheap the payback is a long way off. (How much do YOU pay per kWh?
5) In some situations there are better investments. For example, if you have an old inefficient central AC system, replacing it with a new high-efficiency system may be a better investment. Same for an old inefficient refrigerator or freezer, upgrading windows and doors, insulation, etc.
6) Some people would rather not bother, don't understand the situation, etc.
73 de Jim, N2EY