To figure out how much electricity/energy we use each month…

Like many/most people who have grid-tied PV solar panels…. to figure out how much electricity/energy we use each month I have to do some math.  That’s because the smart meter doesn’t know how much electricity we use directly from the panels.  Some electrons never even hits the electric co’s meter, which can only show numbers for 2 things: (1) the extra KWh flowing out and (2) the extra KWh we need that is coming in (at nights, clouds and cold cold weather)

That’s not enough.  I also have to read (3) the total produced by our PV solar panels.  And then do some math.  The pain in this is that since one’s electricity bill is usually not calendar month, and our smart meter isn’t being read automatically by any device, I have to remember to “read the meter” near the beginning/end of the month.  I can’t use numbers on my electricity bill.

Algebra:

The basic idea:  IN KWh = OUT KWh

(2) ELECTRIC CO METER IN (FROM GRID) +  (3) PV PRODUCED = (1) ELECTRIC CO METER OUT (TO GRID) + X (USED BY HOUSE)

Solve for X and I’ve got it.

Additionally I think it makes sense to divide by the number of occupants in your house before comparing with your friends.  And maybe adjust by things like HDD and CDD (heating degree days and cooling degree days) if they live in a different part of the Earth.

So that’s KWh used per person per month.   We have averaged under 800 KWh per month year round on average for 28 months.  And we have 4 people here.  With 8 living with us for 10(?) months in 2011.

So under 200 KWh per person per month.  For everything, including heating and AC, cooking, lawn mowing and 2 home offices.

It’s hard to compare to most people in the northeast because most people don’t know their grand total since almost no one heats their house with electricity (geothermal or air-source heat pumps) like we do.  So they’d need to add up their gas/propane/wood/oil BTUs used and convert to KWhs.

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