End of Year Energy Accounting

This year we implemented several changes to reduce our consumption.  I posted how we analyzed out energy use and targeted those heavy users for change. That was in Revenge of the Negawatt .  We had our greatest reductions from putting a timer on our water feature pump and adding two three hundred gallon cisterns to help with irrigation.  Moving water is energy intense as is removing it from the air to reduce humidity. We also upgraded our solar water heater system that was  old with the idea of reducing our Propane consumption. We use it for cooking and back up for our solar water heating which fuels our radiant floor system as well as our domestic hot water.

The chart below shows our electric consumption for 2011 and 2012 as well as our electric production from a rooftop 3.78 Kw photovoltaic (PV) system.  Production was amazingly close year to year and our energy savings were 810 Kwh for 2012 compared to 2011. The energy analysis and measures clearly worked.

We used approximately 120 gallons of propane for the year, which produces 12.43 pounds of CO2 per gallon which is 1491.6 pounds or .75 tons of greenhouse gas. ( https://www.epa.gov/climatechange/ghgemissions/ind-assumptions.html )

The surplus production from our Photovoltaic system theoretically saved 1037 Kwh or .80 tons of greenhouse gas from a coal fired power plant. Figured at .078 tons of CO2 per 100 Kwh ( From https://www.epa.gov/cleanenergy/energy-resources/calculator.html )

I did not count the ½ cord of firewood we burn for the year as it has consistently come from downed trees on our property or trees that we had to take down for our building projects.  When trees grow they absorb as much CO2 as they give off when they burn so as long as they are sustainably harvested or come from dead trees they should be a wash in terms of greenhouse gas emissions. They do emit other pollutants though and should be considered carefully in more densely developed areas.

In terms of greenhouse gas we should be pretty close to net zero. In the next year we plan to replace our 12-year-old refrigerator to save more Kwh and to add more production of solar electricity. Ideally we would end up with enough extra to run one of our cars for most of our trips.

If I were starting this house now I would make it more efficient and smaller and use all electric mechanical systems with a net-metered Solar system, which would eliminate the use of Propane.  The radiant floor is nice now and then but we seldom use it and I would go with a mini split or ductless heat pump for the little supplement we need for the passive solar and firewood heat.  Instead of the solar water heater I would go with a heat pump water heater and an extra kilowatt of PV.

Happy New Year! May your energy savings be abundant.