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Tuesday, January 24, 2012

Thanks for buying electricity from me!

by Tom Ferrio

The display at the left tells me that you are are buying about 14 amps of electricity from me. Thanks! And National Grid will even collect the money from you for me so you don't have to write me a check.

This article continues my series on my solar electric installation.


Of course National Grid won't be sending me a check at the end of the month. Especially in the winter, it only generates power like that for a few hours on sunny days. I'll just be paying less. But the negative numbers in the display still look very good to me!

The details behind that reading above was that my solar panels were generating about 2600 watts while we were consuming about 1050 watts in the house. On the sunniest day so far I saw about 30 minutes where the solar panels were putting out their rated capacity of 4100 watts.

Here is a daily graph for the few days since the nice woman from National Grid stopped by to install the bi-directional meter. This includes some considerable time when the panels were covered by snow.


The turquoise negative bars are the daily energy production in kilowatt hours. The green bars show the total consumption in our house and the purple bars show the net purchase of energy from National Grid. (January 24 is a partial day as I'm writing this at 1:30 pm.)

UPDATE: the real-time graph on a partly cloudy day is interesting:

From January 25