The electric utility bills have been received for two billing cycles of operation (April and May) and prove the viability of the installation.
We designed our PV system output to match our historical usage. During the implementation, we made efficiency improvements, dropping our usage below what we expected to generate.
April billing period we generated 123.3% of our consumption. May was 131.4% of consumption. Connecticut is a net-metering state, which means that you push electric into the grid, and you pull electric from the grid - paying on the net consumed. This net calculation is done during the three segments of rates from the utility: periods of peek, off-peak and shoulder. Thus, it's not a true "spin the meter backwards" concept over a billing period.
Our shop opens at 5:30AM and starts consuming electricity, but there is no solar generation at that hour, so we do cause a "demand" of electricity off the grid for which we are billed, the kwh consumed though is zero from the utility - we actually generate an excess of kwhs.
Our utility (United Illuminating) allows the credit to accumulate on your account, and it can be drawn down on - say if the inverter is out of service, or the winter months when daylight is shorter and snowpack on the roof may limit generation. If there is a credit on the account as of April each year, the balance is swept to zero and we are paid for that electricity generated. The price is based on the average spot market for the New England regional electric pool. It gets complicated, but in laymans terms: we get paid a wholesale rate of apx. 6cents per kwh for the excess.
The value in a PV (or other clean energy generating device) is to avoid purchasing electricity at apx. 22cents per kwh. The size of the system design should be close to your consumption to yield the best return on investment.
