Monitoring solar panels

Our new house has 21 solar panels. Because I've never had solar panels before, I wondered how this would impact our electricity bill -- would it be enough to significantly lower our bill? Would it make sense to add more? How much would it help if we didn't use the A/C that much and hung our laundry?

Today I got some hard numbers.

To monitor how much the panels generate, there's a plug that goes into a wall socket and feeds data via ethernet cable to our internet router. From looking at the past couple days' data, it looks like we're generating about 35 kilowatt-hours (kwh's) a day.

Now, this is just one week in April, but from the previous owners' data in years past (still available online) it looks like our system produces a daily average of about 27 kwh's per day across the whole year.

Our usage is hard to guess at, since power is drawn from the solar panels before our system pulls from the grid. However, that number is a bit irrelevant because Hawaiian Electric Company (HECO) uses a "net metering" system.

Basically, "net metering" accepts kwh's fed back into the grid as equivalent to kwh's drawn. So, during the day we put kwh's into the grid. At night we draw kwh's from it. There's no difference in value between a kwh generated and a kwh received.

In the end, the important number is the net draw from the grid, which is shown on the meter. When we moved in, the meter read 5453. Now it's 5235 -- a drop of about 217 kwh's. That's good -- in essence, we've fed 217 more kwh's into the grid than we've drawn from it.

As I understand it, HECO will credit me those kwh's, but not pay me. Not the sweetest deal, but fair enough.

I'm content to have a zero dollar electricity bill in the state with the highest electricity prices in the nation.