How We Calculated Estimates of Energy Use and Possible Savings
Last updated November 2024
Our estimates of typical energy usage and cost savings for our sample Bay Area house were calculated using SnuggPro, an energy-auditing software tool. We also consulted calculators available from the Efficient Windows Collaborative and the National Renewable Energy Laboratory.
Because every structure 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, you can do your own calculations using Snugg Pro or similar applications (we like Snugg Pro best for its straightforward user interface, up-to-date data on energy costs and weather, customization, and overall modeling accuracy).
The initial inputs we used for our hypothetical home included:
- Located in Oakland
- Two-story, single-family house built in 1980 with 2,200 square feet of living space, plus a vented crawlspace
- Occupants: Two adults and two children
- 80 AFUE gas furnace, plus four window AC units
- Thermostat set at 70 degrees for furnace and 73 degrees for AC
- Gas water heater, purchased in 2010
- Standard-efficiency appliances; two refrigerators
- R-12 attic insulation; poor wall insulation
- Ductwork is leaky, with no special sealing or insulation
- Window frames are made of vinyl 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.
