We're now just past midsummer, and I still haven't updated the blog. I guess I must have been saving time.
I'm most of the way through reading "Sustainable Energy-without the hot air".
This book is really good, and best of all, it's available free online at http://www.withouthotair.com if you want to be really light on your resource consumption.
2008-2009 Heating season
For my records, the heating season started last year around September 29, and ended April 20, 2009. I'm defining the heating season as a week where we used on average more the 50kWh per day of gas, our primary heat source. We installed a new 90% efficient condensing boiler in February 2008, and unbelievably it actually did use 20% less fuel than our previous boiler that was installed when the house was built in 1985.
I also installed a weather station just over a year, ago, and using software from http://www.wieser-software.com/metstats calculate that the number of degree days during the same period was 2134 calculated against a base temperature of 19.5°C. That's an average of 10.51 degree days per day for the 203 day period.
During the period, we averaged 16.3 kWh of electricity between 7AM and 12:30 AM and 7.2 kWh during the off peak hours. We also averaged 71.9 kWh of gas per day. So, our total energy usage was 95.4 kWh per day, or 9.08 kWh per degree day.
I've also been keeping track of a neighbours house, but they keep their thermostat at 19.5°C, which comes out to an average of 12.51 (by adding 2 to our degree day figure, due to the temperature difference). Their usage was 106.7 kWh per day, or normalized for degree days 8.5 kWh per degree day.
Their house is a different shape from ours, and has recently been practically rebuilt with to new building code standards. It looks like our house is 6.8% less efficient than theirs, however due to our house being heated to two degrees less, we managed to consume only 93% of the energy they did, so it's proof it is worth turning your thermostat down, if you want to save money.
Next year's challenge: See if we can cut next season's kWh per degree day.
This calculation isn't strictly correct yet. To do this completely accurately, the base line load for each house when zero degree days are seen should be subtracted before the calculations, to only include the extra cost of heating.
Looking at the figures from the beginning of June, both houses used an average of 26 kWh per day during the non heating season, bringing their house to 6.45 kWh per degree day, vs our house at 6.6 kWh per degree day, making our house only 2.3% less efficient than theirs.