How sparing of greenhouse gas production is going all-electric for new home construction? Surprisingly, the answer varies depending on how the energy is used. The complexities of picking a less-polluting future are not beyond the understanding of Los Altos residents. There is laziness in not looking into the details – and worse, choosing a course that is more polluting than our current status.

An estimated 50-60% of energy used in California is derived from burning fossil fuels (see below for supporting data). The good news is that growth of solar and wind power will gradually reduce fossil fuel share over the coming decades. Two important data sets to be aware of are the fuel efficiencies of producing electricity from a variety of sources and the fuel efficiency of gas versus electricity to heat air and water.

Gas, coal, nuclear and diesel produce electricity by heating water to turn a turbine. Much of the energy is lost as heat. An abbreviated list of the efficiency of converting fuel source to electricity:

• Gas: 32-44% more efficient, with some new plants hoped to push the number to 60%

• Coal: 32-34% (not currently used in California)

• Nuclear: 38%

• Diesel: 35-42%

Now let’s explore the efficiency of electric furnaces and water heaters compared to gas furnaces and water heaters. Older furnaces and water heaters were less efficient than newer ones.

• Home electric water heater: 90-95% more efficient

• Home gas water heater: 80-95%

• Home electric furnace: 95-98%

• Home gas furnace: 80-95%

The real math on efficiency for electric water heaters and furnaces starts at the power plant. In addition, there is an average loss of 9.2% of energy over transmission lines in California.

There is continued loss of energy within the walls of our homes that varies more widely (3-10%).

For 40-50% of California energy coming from renewables, electric water heaters and furnaces are 0-15% more efficient than their gas-powered counterparts.

For the 50-60% of California energy coming from fossil fuels, electric water heaters and furnaces are 54-58% less efficient.

It is surprising to see that for heating used in the home, gas is often still more efficient than electricity. Until solar and wind replace fossil fuel use in power plants, using electric furnaces and hot water heaters will require 2-2 1/2 times as much fuel as burning gas directly in the furnace or hot-water heater. In California, this is a very large amount of carbon dioxide and other pollutants.

On a local scale, increasing output of greenhouse gases at a distant power plant might appeal to some. However, on a global scale, it is short-sighted and reflects poorly on the residents of Los Altos.

Fortunately, solar and wind power generation are likely to continue to grow in California. As less power comes from burning fossil fuels, there will be a point where all-electric appliances will be more efficient. Ultimately we all need to use less.

California produces 71% of the energy it uses, with 21% coming from Southwest states and 8% coming from the Northwest.

Of the 29% of energy imported from outside California, 68-100% of that energy comes from coal or gas-powered plants. This is driven by surge demand on hot or cold days as well as work-week industrial/commercial demand.

Andy Staatz is a Los Altos resident. He collected his statistics from several sources, including the California Energy Commission, Inside Energy, PV Heating & Air, the U.S. Department of Energy and Reliable Water Services.