Monday, March 14, 2011

One Month of Solar

Usually our electric meter gets read on the 14th, which would be today. Since last month, I've been keeping track of daily electric use by reading our meter on the side of the house. It's interesting how aware you become of electric use when you do that.....an extra load of laundry, dishes, etc.... it all adds up. What I'm trying to see is if the effects of the solar hot water system can be seen in the bill... I think they can, and it's more than I expected. Of course there are other factors like weather that play in..but averages speak volumes. I have plotted in excel, every electric bill for this house over the last 10 years (January 2000). For the 28 days spanning 14 February to 14 March the bill has averaged 1537kWh with a low of 1247kWh last year and the runner up of 1290kWh in 2000 when we 1st moved in. This month, the bill was only 1035kWh! The lowest bill EVER for the period since we moved in. That is roughly 17% down from the low and 32.6% down from average.

The days are still pretty short and the sun pretty low in the sky...the system is not supplying all our hot water under these conditions and will only get better throughout the spring and summer. I'm looking forward to seeing if the trend continues.

As for calibration, the control unit is clearly under calculating the kWh generated...by how much I'm not sure. I believe this is because I have the incorrect flow rate programmed into it. As I take more data I'll see if I can predict and back into the correct calibraction factor...for now, it is good enough to tell a good day from a bad day and act as a diagnostic.

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