How We Calculated Estimates of Energy Use and Possible Savings
Last updated December 2020
Our estimates of typical energy usage and cost savings for our sample Chicago area house were calculated using the U.S. Department of Energy’s (DOE) excellent Home Energy Saver pro tool. We also consulted calculators available from the Efficient Windows Collaborative and the National Renewable Energy Laboratory.
Because every building is unique, and even small differences in features of various residences can sharply change how much energy each uses—and potential savings—our estimates won’t apply exactly to your home. For more personalized info, do your own calculations using the Home Energy Saver pro tool.
The initial inputs we used for our hypothetical home included:
- Two-story, single-family house built in 1980 with 2,200 square feet of living space, plus finished basement
- Occupants: Two adults and two children
- Gas furnace, central A/C, both installed in 2010
- Thermostat set at 70 degrees for furnace and 73 degrees for A/C
- Gas water heater, purchased in 2015
- R-11 attic insulation; wall insulation amounts unknown
- Ducts run through conditioned spaces with no special sealing
- Window frames are made of aluminum and have two panes but are leaky; doors do not have weatherstripping
We introduced various energy-saving improvements to determine how each affected consumption and costs. We made these changes one at a time, in isolation from one another. Note that, especially for heating costs, if you make one change (say, improve your attic’s insulation), it will reduce overall energy usage and the benefit of making one or more additional improvements (install a more efficient furnace, run ceiling fans, etc.) will be diminished.