Friday, September 25, 2009

Solar Power - Monitoring Consumption

We finally got Solarcity to install the consumption monitor, and we are now figuring out what the various bumps in the graph correlate to in terms of appliances. The first graph shows consumption on a hot day, with a portable room A/C unit left on all day. There is a characteristic bump in the morning that seems to correlate to re-heating hot water after showers, and random bumps during the day that are probably the hot tub cycling on to filter and maintain water temperature.

Another day where we didn't leave the A/C unit on shows much lower consumption. One of the common psychological effects of measuring something is a compulsion to optimize it, so we are now challenging ourselves to try and reduce consumption...

Since we are now on a time-of-use meter, the cost of electricity at nights and weekends is very low, and the cost in the afternoons during the week is high, but that is when we are generating more than we are using, so in $ terms, the meter is running backwards at high speed, and forwards slowly. This also makes it very hard to calculate the cost savings.

Total generation for the month is looking good. We turned on the system right at the start of the month, so the lifetime total includes a week or so before the output monitoring started to log data, and you can see the last few days of consumption data. We have had typical (for us) weather, sunny from the start of the day most days. We drive down into the clouds each morning. The drop off a few weeks ago was a cloudy spell that included about 0.25in of rain, enough to make sure the solar panels are nice and clean. There is a slow downward trend in the daily output, since the days are getting shorter and the Sun is lower in the sky every day. It's around the equinox at the moment. Over-all, I'm happy with how much energy we are getting, I expected to get longer effective days than most people, and it looks as if we will be generating about 600 KWh this month, our typical consumption has been around 1000 KWh.

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