When we think about building newer, greener households, there is a tendency to focus on the house going all electric. After all, if a house does not burn any fossil fuels, it follows that the carbon footprint of the household should be zero, right?
This kind of carbon accounting, however, fails to include any greenhouse gas emissions that occurred prior to the point of consumption. When you use electricity to watch TV or heat your home, the energy was generated from an “upstream” fuel source. This generation and subsequent transmission to your house means that every time you turn on a light, there could be associated greenhouse gas emissions.
Let’s look at the U.S. electricity mix. In 2011, more than 42 percent of all electric energy was generated from coal, the most carbon-intensive fossil fuel used for electric generation. Natural gas, which has a lighter greenhouse gas footprint, represents 20 percent of the electric energy generated last year. The remaining generation came from nuclear (19 percent), hydroelectric (8 percent), and renewables like solar and wind (less than 5 percent). But what does this mean for greenhouse gas emissions related to home energy use?
In a recent report, Squeezing Every BTU, we tried to calculate exactly what the greenhouse gas impact of a typical new home might be. The Policy Analysis team here at AGA modeled an “average” household by calculating what energy would be required to heat the home, for water heating, for cooking and for clothes drying. We assumed an average sized home in a moderate climate, and the appliances all met the minimum standards for efficiency. For the electric home, we assumed the house used an electric heat pump for its winter heating needs.
The next step was to calculate the amount of fuel required to meet these energy requirements. We considered natural gas, electricity, fuel oil and propane. The final step calculated the greenhouse gas impact from this fuel usage. We made sure to include all “upstream” emissions from the production of the primary fuel to its transportation (truck, rail, pipeline), as well as any emissions associated with electric generation, and eventually emissions related to the final delivery to the consumer.
By combining all the upstream source emissions with the end-use fuel consumption, we were able to evaluate the full-fuel-cycle impact of a typical household’s energy requirements on greenhouse gas emissions. This is what we found.
On average, a typical household using natural gas performs the best. The natural gas household modeled had four percent fewer greenhouse gas emissions compared with an all-electric household. Compared to fuel oil and propane respectively, the natural gas household emitted 27 percent and 16 percent fewer greenhouse gases, . The figure above captures the total amount of greenhouse gases associated with using the specified energy source for space heating, water heating, cooking, and clothes drying, as measured in metric tons of carbon dioxide equivalent per household per year
The bottom line is that the direct use of natural gas is and should be seen as a carbon mitigation tool. Replacing less efficient and more carbon intensive equipment with high efficiency natural gas can lead to substantial decreases in greenhouse gases. With natural gas prices dropping, consumers can save money and reduce their carbon footprint by using natural gas directly in the home.
For more on this and other market and policy issues related to the direct use of natural gas, see AGA’s recent report Squeezing Every BTU: Natural Gas Direct Use Opportunities and Challenges.