The following spreadsheets explore the energy use of the cabin. Through various conversions and calculations, I determined that the cabin uses an average of:
55 kWh per sq meter per year.
This compares very favorably with the Passive House goals of:
120 kWh per sq meter per year.
Note that the cabin is NOT a certified Passive House! Merely that I embrace the goals of low energy use. It’s important to note that most of the 15,000 to 20,000 Passive House projects claimed for Europe, are not actually certified either, but are designed towards P.H. goals.
Here’s the proof, the January 2013 (the coldest month) PG&E electric bill is $24.53!
And the January PG&E Gas bill is $25.79!
The following is a graph for one 24 hour period, April 18, 2013. Electric usage is plotted over average outdoor temperature. You can see, in April, the outdoor temperature doesn’t have anything to do the electric usage. It makes sense that there’s a baseline, then usage kicks up when I get home from work at 6:00, and probably peaks when all the lights are on and I’m taking a shower (the bath exhaust fan and the combustion air fan for the 95% efficient water heater are running – but still the whole house is only consuming 300 watts). The mysterious thing for me was the two-hour spikes in the base line; I figured it out – it’s the refrigerator! But since it only draws 1,400 watts when it’s running, and it only runs 10% – 12% of the time, the energy savings won’t pay for a new refrigerator in twenty years.