Having just gotten our PV panel installed on our roof this year, this is fresh in my mind. Of course everyone is doing it -- electricity in Hawaii is insanely e

Having just gotten our PV panel installed on our roof this year, this is fresh in my mind. Of course everyone is doing it -- electricity in Hawaii is insanely expensive. Before we turned on the system, we paid $200/month for power! And this is in a house with no heat and no AC. Do they have to buy the power? Yes, but not without limits. The system is built on "net metering". Every kWh we deliver to the grid can only go to offset one that we already have or will use. If your system is so large so as to make you a net producer of energy when averaged over a whole year, you will be giving that away to the utility for free. The rules also limit installation of PV systems to a level that will not exceed the minimum daytime load on the local circuit, exactly because there is nowhere to store the power. So every kWh they get from us is one they would otherwise have to generate to supply to one of my neighbors. It's clear that the utility companies aren't happy with this. But studies have shown that these "extra costs" the utilities talk about being saddled with are offset by savings to them as well. Solar power typically produces power during times of high power demand, so the net effect of solar is actually to even out the daily load variance. This is good for the utility because they need to make sure they have capacity to handle peak load, even if it's only for a small fraction of the time. These "peak power" plants are expensive, because you almost never get to operate them. When PV reduces peak load, they don't need these plants and this is a net win for them.