After recent monthly electricity bills of $0.68 and $3.61 (or whatever the exact numbers) this month the electricity bill went WAY up. $26.21!!! We still had quite good numbers on the PV production side, and didn’t use much, but since there is no net-metering (our electricity supplier is a municipal and so is exempt from the MA law requiring that electricity companies allow net-metering for grid-tied PV and wind systems. I’m not really complaining, just explaining.
So anyway, our billing is “time of use” so any time the sun isn’t shining and we use electricity, we pay for it full price whereas when we have extra on sunny days that we put back into the grid, we are paid back for this on $0.44550/KWh (roughly 3 or 4 times less than what we pay).
So that’s basically how we end up with a $26.21 electricity bill even though we put 571 KWh back into the grid and only used 381 from the grid.
If there was net metering I suppose our bill would be something like:
571-381=190KWh extra made, so…
Min charge from the electric company is: $21.63
– 0.15 x 190 (the rough amount paid per KWh is 15 cents)
= 21.63 – 28.50 = -$6.87 (credit)
I guess one could calculate the amount this will likely add up to over one year. Rough assumptions:
1. Exactly net-zero for the year
Our PVs make exactly the amount expected from the “avg year” from the “PV Watts v1″ calculator on the web (I believe it is ~9000KWh for our 6.9KW PV system)
2. Worst case scenario: we use exactly 0 KWh of our electricity we make during the day — everyone is away and somehow the house magically uses nothing in phantom loads (impossible since the smoke detectors have to run at the very least!) — and therefore we have to buy 100% of our electricity (at night).
If net-metering, our bill for the year would be exactly $0.00. Simple.
With our current arrangement it will be (worst case) per month: $21.63 + 0.15 * (9000/12 – 200) (Note: -200 since 200KWh are included in the $21.63 monthly base charge and we will likely always use at least this much in eves)
That’s per year = 12 * 134.13 = $1609.56
In reality it will be much less than this because we DO use a lot of our electricity during the day. So let’s say 1/2 that… $800.
$66 per month.
And that’s for everything, heating/cooling (heat pump), all appliances, cooking, hot water (also heat pump), mowing, well pump, etc, etc.
Anyway, I’ll report back in a year with the actual numbers.