Thursday, 9 January 2014

PV chart

We downloaded today’s data from the inverters this evening, and we can see the electricity we generated, from sunrise (8:06 GMT) to sunset (16:06 GMT), with data points every 5 minutes.

vertical scale: kW; green line: total energy generated; blue line: energy generated from top row of 15 panels; brown line: energy generated from bottom row of 12 panels

The top row of panels didn’t start generating until later, as they need a bigger voltage to kick their inverter into life.  It was cloudy and gloomy in the morning, but around midday, the low winter sun came out, and generation leapt to 4kW.  The afternoon stayed sunny, and the curve is essentially tracking the setting sun, with occasional cloud.

The brown line is somewhat less than 12/15 = 80% of the blue one, partly from shading from the scaffolding poles (due to be removed tomorrow), and partly from being lower on the roof.

That’s a total of 9.5 kWh generated on a winter’s day, when the sun was above the horizon for a total of 8 hours, and it was cloudy until noon.  So that’s about £1.30 due from the feed-in tariff.  Not bad.  Now we have to replan our electricity usage patterns to coincide with when the sun shines.


  1. > "Now we have to replan our electricity usage patterns to coincide with when the sun shines."
    I've seen arguments saying that PV panels should be installed on the west sides of buildings, rather than south, because that gives more energy into the evening, coinciding with when people use more energy.

    1. Yes. Our roof, although very nearly directly due south, is just a little bit tilted due east, which makes it slightly less than optimal. And at the moment, of course, there is no sunlight at all in the evenings!