Thursday, January 1, 2015

Energy Consumption for 2013 and 2014

Happy New Year everyone!  We've been living in Our Connecticut Passive House for a little more than two years now.  I began detailed electricity monitoring in January 2013.  Now we have complete information for all of 2013 and 2014.  In these two years, our 10.78kW solar panel system produced 24,113 kWh of electricity while we used 23,384 kWh.  So, we produced 729 kWh more than we used.  Yippee! The house is completely electric.  No oil, gas, wood or any other fuel is used. 

One of the great things about living in a net-zero house, i.e. one that produces all the energy it uses, is that our total energy bill consists of the CL&P (our electric utility company) fixed charge of $16 per month for being connected to the grid.  This is a pretty impressive result given that we have a decent size house (2800 sf of finished floor space) and live in a cold climate.  We're looking forward to reaping the benefits of our investment in energy efficiency and solar power for entire lifespan of the house.

The charts below show electricity production and usage for calendar years 2013 and 2014 respectively.  You can see that in 2013 we produced more than we used (by 1266kWh), while in 2014 we used more than we produced (by 537 kWh).

Our usage in 2013 was 11,136 kWh.  Usage increased by 1112 kWh to 12,248 kWh in 2014.  This entire increase can be explained by the increased heat pump and HRV consumption in the very cold months of January and February 2014.  The average temperature during Jan and Feb 2013 was 27 F while in 2014 it dropped 4 degrees to 23 F.  Another factor influencing the additional consumption was turning up the indoor thermostat from 68 F to 70 F during 2014.  There also may have been a decrease in sunshine heating the house indicated  by the less impressive performance of the solar hot water heater in Jan 2014 compared with 2013.  Solar PV performance was also weaker in 2014 during Jan, but it's difficult to say how much of the performance difference is due to snow covering the panels on the roof.  The solar hot water panel is on the ground, so it's easy to clear the snow off it.

Electricity production was down 692 kWh in 2014 compared to 2013.  In 2013 we produced 12,403 kWh and in 2014 we produced 11,711 kWh.  Most of this difference is probably due to a snow covered roof in January and February 2014.

So, two years into the journey, it looks like a Passive House's energy efficiency combined with solar energy generation can produce a house with a zero net carbon footprint that costs almost nothing to operate.  It's not just hype.

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