MtnDon
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# Posted: 15 Dec 2010 15:21 - Edited by: MtnDon
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If you already have a connection to the power grid and do not want to invest in batteries I don't believe there is any cost advantage to installing PV modules and trying to use the DC power from them for small DC appliances. I believe you would need at least one battery in there for the charge controller to sense how to configure the output, at least with an Outback FM60 charge controller you would need a battery, as the FM60 reads the voltage from the batteries to set itself to the correct output mode.
Perhaps if the power company offers net metering you could consider a grid tie installation? When you have excess generation the power company buys your power. When your uses exceeds your generation ability you buy from the power company. No batteries required, but the modules must be large enough to feed the power grid through a grid tie inverter. Some but not all, power companies will actually send a check if your system produces a monthly excess. This varies widely so best to check. Mine does and we have an annual agreement that sets the payback rate.
While it is nice to have a net annual power bill that approaches zero, it is actually not a greatof a return on the investment in equipment. Although it may be better than some stock market investments these days.
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