We have lot’s of people inquiring about the performance of the house this winter.  The only month that we have reliable data for is December, because prior to December we still had a lot of work going on and people coming and going all day.

The modeled demands for the month of December were 959kWh for heat/pumps/ERV plus 397kWh for lights, appliances and all plug loads = 1356 kWh.

Our actual use in December was 1461kWh.    This puts us 105kWh over our expected consumption.

December had much less sun, but was warmer than typical.  The house needs sun to function anywhere near net zero.  Our PV array only produced 122 kWh for the month, less than 1/2 of what was modeled.

So, the net energy for the month was 1,339kWh, plus some wood burning.

The cost of that energy from Hydro Ottawa was $121.  The sale of our exported energy earned us $97.85.  So the net cost to live in the house for December was $23.15.

Interesting note on the house loving the sun.  In January we had a day where it averaged -19 C outside but was sunny  - like this photograph below.  The house started the day at 19 C inside, and climbed to 21 over the course of the day without ever demanding heat input from the radiant floors.  That day we added over 6 degrees to the solar storage tank, so that night when there was some heat demand, it all came from the solar storage tank.  More on this system in future posts, but it is really cool to see a 40 degree temperature difference between inside  and outside with completely passive systems.

The house loves sunshine