Solar House

This table shows the actual usage and cost for energy from 2000 through 2005, along with some summary statistics.

 Year Gas CCF Gas \$ Electric KWh Electric \$ Water CCF Water \$ 2000 840 475 6352 596 78 287 2001 829 484 6817 630 98 352 2002 957 669 7889 739 96 371 2003 896 698 7984 746 91 387 2004 577 543 7358 679 80 387 2005 517 683 7719 720 77 397

• These figures are for the total 3800 ft² of conditioned space in our house, which has three bedrooms, three baths, two adults and two small kids, all the usual appliances including a separate freezer, no outdoor sprinkler system. Gas is used for space and water heating, cooking, and clothes drying.
• A new kid was added in spring 2001.
• Central AC was added in spring 2002.
• Solar hot water and space heating was added in February 2004, resulting in a 38% reduction in natural gas use (average use in 2000-2003 was 881 CCF/yr, and in 2004-2005 was 547 CCF/yr).
• Gas rates have gone up from \$0.44 per CCF in 2000 to most recently \$1.31 per CCF

The bottom line:

• Budget energy costs from 2000-2005 have been: Gas - \$57/month, electric \$60/month, water \$33/month. Total for gas, electricity, and water is \$150/month
• Gas use for the same size house built to 1992 Energy Codes would be about 1650 CCF/year. We use at least 60% less than that.

What about carbon emissions? Based on our use of natural gas, electricity, and gasoline for driving, here are the results from an emissions calculator at safeclimate.net:

 Quantity Used per Year Energy Content (megajoules) Carbon Emissions (lbs) Natural Gas (therms) 550 58000 7171 Electricity (kwh) 7700 27700 12166 Gasoline (gal) 400 48500 7824

The total carbon emissions is about 27,160 lbs/yr, or about 600 lbs/person/month for our household, not surprisingly less than average. Note that electricity is the largest contributor (and it could be higher since I think the emissions calculators use emissions per generated kwh as opposed to emissions per delivered kwh) and natural gas and gasoline are about the same.

Regarding energy content, it seems like electricity is low, but this is just the energy content of the kwh we used, not the energy content of the fuel burned to produce those kwh.