Monday, 22 April 2013

Snow in April

It snowed in the night and the there was a couple of centimetres left on the roof on the morning of April 11th. I had to go to work and didn't have time to clear it, so there's an opportunity to see how much less electricity we generated and the value of clearing snow. 

Here's a comparison between the generation on the snow-covered day with the day before, which was otherwise similarly sunny.
In these graphs, the pink is the electricity consumption, highest in the wee hours when the eco cute is making us hot water. The blue is the generation, peaking with the rising sun. Notice the difference bewteen 6 and 9am.

It looks like the snow was still there until around 9 o'clock, stopping the rays of the sun reaching the panels, and stopping any chance of the heat melting it from beneath.

time Generation / kWh
11th 10th Loss
8:00 0.4 3.1 2.7
9:00 4.0 4.9 0.9
10:00 5.9 6.0 -
total loss 4.1

The total loss was 4.1 kilowatt hours and we're getting 48 yen per kWh, so that's a couple of hundred yen. Is it worth spending five minutes clearing snow off the bottom of the roof for that?