Spring is in sight and we have just done the analysis of February’s performance with our solar PV (4kW) plus Wattstor battery (6kWh) system. The longer days and the sun being higher in the sky have started to make a significant difference despite much of February being gloomy and wet. Some of our evening cooking and lighting (once the sun has set) is now supported by Bert-the-battery rather than from the grid.
Chart 1 shows the daily Wh averages for each month since May 2016. Our daily consumption is staying relatively steady at just over 8kWh/day. (It does vary somewhat day to day depending on the significant effect of charging our Twizy which also has a 6kWh battery to fill. We try to charge the Twizy when the sun is contributing the most to avoid either taking from the grid or depleting Bert-the-battery in order to fill another battery. In the winter, that’s hard to manage.)
Chart 2 shows the percentage of our daily electricity consumption which comes from each source – the solar panels directly, the solar via the battery or directly from the grid. In February, 31% of our consumption was covered by the solar and battery combined – the best performance since October. The battery alone contributed 12.5% of our consumption. Because the lead acid batteries spend most of their time on absorption as opposed to bulk charging (to protect themselves), we aren’t capturing as much of the solar into the battery (for later use) as we would like. As Chart 1 shows, the actual solar generation was up to 50% of the overall consumption but the amount of the solar generated power which the battery could absorb in real time is restricted so roughly 25% of it was passed to the grid for others to use. We try to view this in a generous spirit!
We now look forward to the long sunny days of March (typical weather here in Wales of course..).