How big is your pile of coal?

How big is your pile of coal?
July 17, 2012 Anne Maertens

The first half of 2012 has been the hottest on record in the U.S., and in many regions, people are blasting their air conditioner 24 hours a day to keep their homes comfortable and safe. Not only is the electricity used to power these air conditioners expensive, but in many regions of the country, it is generated by burning coal.

Unfortunately, converting coal to electricity is an inefficient process with 70% of the coal’s potential energy lost during the conversion to electricity at the power plant and another 9% lost over the power grid. Since only 28% of coal’s potential energy is delivered to the home, using that energy efficiently can have a major impact in reducing the amount of coal that each home uses.

Our Math

To cool the average home in the Southeast, a central air conditioner consumes 4,050 kilowatt-hours (kWh) annually. For electricity generated from coal, the process of delivering those kWh’s looks like this:

  1. Start with 4,870 pounds of coal, which contains the equivalent of 14,830 kWh of potential energy.
  2. Convert that coal to electricity at a typical power plant and you lose 70% of the potential energy, which brings you to 4,449 kWh.
  3. Of the remaining potential energy, 9% is lost as the electricity travels along the grid, resulting in 4,050 kWh delivered to the home.

Given the inefficiency of generating and delivering electricity from coal, it’s important for people to be smart about how they use the kWh’s that reach their homes. By making cost-effective improvements to their homes’ energy efficiency, homeowners can reduce the amount of coal it takes to cool their homes this summer.

By upgrading the central A/C for an average home in the Southeast from a SEER 10 to an ENERGY STAR rated central A/C with a SEER of 14.5, a homeowner could reduce the home’s cooling consumption by a third to 3,300 pounds of coal.

Combining this A/C upgrade with duct sealing and duct insulation as well as sealing the leaks in the home’s exterior could reduce the amount of coal burned to cool the home to just 2,000 pounds–less than half of what the average home in the Southeast consumes.

Reducing the original coal pile to 2,000 pounds prevents nearly 6,300 pounds of carbon dioxide, 36 pounds of sulfur dioxide and 16 pounds of nitrogen oxide from being emitted into the atmosphere annually (Environmental Protection Agency). It could also save the home around $300 on their electricity bills each year.

To find out how you can reduce your coal pile this summer, complete this easy online home energy survey to find out what upgrades make the most sense in your home. If you decide to upgrade your air conditioner, don’t miss out on rebates from utilities and governmental agencies in your area.

If you happen to live in an area of the country that doesn’t use a lot of coal to generate your electricity, you’re not off the hook. Similar calculations can be made for any fuel source for electricity: we encourage everyone to use energy in their home wisely.

Assumptions: This is a simplified calculation based on average home conditions and use, as well as average climate data; therefore, actual annual consumption may vary from these estimates depending on home location and size, the SEER rating and size of the current AC unit and the current year’s weather conditions. Assumed characteristics of the average home in the Southeast:

Assumed characteristics for upgraded home:

  • 1,700 square feet built in 1982
  • Central air conditioner, 3 tons, SEER 14.5 (current ENERGY STAR standard)
  • Programmable thermostat
  • Two-story home
  • Duct leakage decrease to 5% (from 15%); increase in duct insulation to R-8 (current ENERGY STAR standard)
  • Reducing overall home exterior air leakage decreases cooling usage by 20%.

Conversion factors using weighted average of energy content from the four major coal types found in the U.S.:

  • 3,412 BTU/kWh
  • 10,392.5 BTU/lb of coal
  • 0.3283lb/kWh