The graph above shows our progress so far. It contains the annual carbon emissions measured in metric tons CO2 for each of three categories of suburban living: electricity, natural gas (space and hot water heating, cooking) and two cars, from 2002 to 2009, 7 years. Before going into details, a few words about how the graph was generated. Since we are obviously not yet at the end of 2009, the figure for 2009 is an estimate based on usage so far. Likewise, the figures for 2002 and 2003 are estimates. We bought the house in fall 2003, and the estimates of gas and electricity usage are based on 9 months of data for 2002 and 2003 given to me by the previous owners, and the last month in 2003 from our own usage, before we introduced any energy saving measures. Other than that, the gas and electricty figures from 2004 through 2009 are as accurate as PG&E can get it to me.
Likewise, the figure for the car in 2002 and 2003 is based on our cars and not that of the previous owners, so the numbers for those years are a composite. They are what we would have used had we lived in the house with our cars. The car figures are based on the approximate measured miles per gallon of the cars we owned, a milage of around 10,000 miles per year on the higher mpg car and 8,000 miles per year on the lower mpg car. Again, this is an estimate but one I've found to be fairly accurate for our family.
As the figure shows, we've managed to reduce our carbon footprint from over 12 metric tons to just under 6 metric tons in 7 years! That amounts to a 55% reduction. The graph below shows our year by year percent reduction.
Our experience shows why talk of postponing radical carbon reductions until after 2030 is such nonsense. The Waxman-Markey bill proposes a mere 17% reduction in 10 years, by 2020. Even people involved in green remodeling have proposed a 25% reduction in 20 years for residential buildings, and that based on buildings from the 1950's where the building codes for insulation were nowhere near what they were even in the 1970's when our house was built. These are timid, half hearted proposals that are not going to solve the climate problem. We need massive reductions, and we need them soon.
A few high level observations about our experience (but details to come in future posts):
- Renewable energy and alternate energy cars are a vital and important part of the mix. They get reductions on the order of 20, 30, up to 100%. The massive reduction in our electric emissions between 2003 and 2004 was due to installing a solar PV system, and we are currently undergoing a similar but smaller reduction in gas usage due to a solar hot water system installed this year.
- But changes in lifestyle and operation are also quite important too. For example, we originally sized our PV system to replace 2/3 of our electric bill. Then in 2004 we took out a pool and put in an energy efficient electrically heated hot tub. The pool had two large electric pumps which went on minimum once a week. We keep the hot tub at 80 degrees until just before we use it, it's on 220V so it heats up in about an hour. The solar PV system subsequently covered around 115% of our electric use, so we now have some spare capacity. Likewise, setting the thermostat to 68 degrees in the winter and turning off the furnace pilot light in summer reduced the gas bill by about half between 2003 and 2004.
- Electrical efficiency improvements like Energy Star appliances, CFLs, etc. seem to help but heating efficiency improvements like double pane windows don't. We had double pane windows installed in 2004 and saw no difference in our gas bill, though the house is less drafty and quieter. On the other hand, the electrical efficiency improvements we installed in 2004 resulted in a modest additional drop in our electrical usage, which added to our PV surplus.
- Natural gas emissions seem to be more difficult to reduce than others. Auto emissions can be reduced by simply not driving as much. And PV is a really simple way to reduce emissions from electricity. But there doesn't seem to be a renewable energy technology for the uses to which natural gas is put that is as easy to install in an existing home and as cost effective as PV.
We are clearly on the way to 80% and maybe even to net zero!