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Question:

How to hook up a portable generator to the grid to supplement my solar system?

I want to run the generator just enough to feedback enough kilowatts to make my annual bill zero usage.

Answer:

The solar system has the electronics to make sure that power sent to the grid is exactly in phase with the grid. Your generator is not set up to do that. The electronics involved must control the speed of the generator so that the two phases can be synchronized before you can feed back to the grid. If you do not then you will probably destroy the generator, and just might melt the wiring between the generator and the grid.
Guide okorder
Power and gas companies also charge you a monthly fee for the meter on your house.
I'm not sure what you have in mind is a good idea. If you mean hook up a gas-powered generator, that will almost certainly be more expensive than grid electricity, and worse for the environment. Where I live in California, it is impossible to pay zero to the electric company while connected to the grid, that's just the way the program works. We are billed a minimum usage of 1 kWh a day, whether we use it or not. Also, having a gas generator ultimately tying back to the grid would classify me as a small generator, and require an agreement with the power company similar to the one I have for solar alone. I don't know what the rules are where you're located, but maybe they follow a similar philosophy? EDIT: okay, I see now. At least for my system, the entire system must be approved as a whole. If I want to alter the system, even by adding a couple panels, I'm supposed to notify the power company. Also, where I live, solar is treated differently from other forms of generation. Solar qualifies for net metering. If I wanted to be a small generator from (say) hydro, my output would be bought at a paltry rate, not even exchange at the same price that I buy at. Your hybrid system, with the generator rectified into DC then passed through your grid-tied inverter, might fall under the same classification, depending on where you live. Also check your inverter warranty to see if it might be voided by connecting to a diesel generator.
Definitely not a good idea to do. Also illegal in most areas. Code dictates that generators be connected to a home electrical system with an isolation switch to prevent feeding electricity to the grid. That way if power is out, the lines will be dead . If power were out and generator not isolated the lineman could be electrocuted. Next is cost. I have a standby generator that runs on natural gas. HAd an extended power outage last fall. Cost about $2.00 an hour to run it.

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