Energy Report, June 2010


Solar electricity produced: 593 kW h (19.8 kW h per day)
Electricity consumed: 278 kW h (9.3 kW h per day)


For the month of June we produced 2.13 times as much electricity as we consumed, and we exported a net surplus of 306 kW h. Our energy consumption per day was just a little less than May but solar energy production was 10% lower. As in the previous month, some of this decrease is due to cloudy weather and some of it is due to increasing sun angle. Because our panels are oriented with a relatively steep 60-degree slope, energy production dips at the summer solstice. We expect next month's production to be back up as the sun angle is getting lower again and we typically get sunnier weather later in the summer.

The following graph shows our cumulative electricity produced (red) and consumed (blue) in watt-hours over the first 3 months of operation since the PV array was activated on April 1st.

The solar heat collectors continued to collect just a little more heat than we used for hot water, and the system's high limit controls kept the tank from going above 140 degrees F. It is actually warmer than we want it to be, because it is adding some unwanted heat to the house through the insulation around the tank. For the next month we'll turn down the maximum temperature to about 125 degrees F so the tank doesn't stay warmer than we need for domestic hot water.

The graph below shows the temperatures outside (red) and inside the house (blue), recorded each morning and evening. The interior remained comfortably cool all month despite some daytime highs around 90 degrees (the mid-day high temperatures were not recorded but were somewhat higher than the evening temps shown on the graph). Near the end of the month, we took advantage of some unseasonably cool nights to cool down the house with nighttime ventilation, in anticipation of warmer weather in the next few weeks. We also kept all the windows open during the daytime when the daytime temps stayed in the low 70s. Overall it was very comfortable inside, and on hot days coming inside felt like stepping into an air-conditioned home.


This page was updated on Wednesday January 11, 2017