Enter your home's insulated area, current and target R-values, heating degree days, and fuel type to estimate your annual and 10-year insulation energy savings. The calculator also shows estimated greenhouse gas reduction, giving you a clear picture of both the financial and environmental impact of upgrading your insulation.
Estimated Annual Savings
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10-Year Savings
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Heat Loss Reduction
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CO₂ Reduction (lbs/year)
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BTUs Saved Per Year
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R-value measures resistance to heat flow — the higher the R-value, the better the insulation. Savings are proportional to the reduction in heat loss, which follows the formula: heat loss ∝ 1/R. So upgrading from R-11 to R-38 dramatically cuts heat loss and therefore the fuel needed to maintain a comfortable temperature.
Heating Degree Days (HDD) measure how cold a location is over a year by summing the degrees each day's average temperature falls below 65°F. A higher HDD means more heating demand. You can find your local HDD value from NOAA's Climate Data Online or your utility company's website.
Not all fuel burned by your furnace converts into usable heat — some is lost through exhaust and inefficiencies. If your furnace is 80% efficient, only 80% of the fuel energy actually heats your home. A more efficient system means you need less fuel per BTU of heat delivered, so the fuel savings from better insulation are also slightly lower in dollar terms.
The calculator may slightly overestimate savings because it doesn't account for internal heat gains from people, appliances, and solar window gains. In colder climates with high HDD, this error is small. In milder climates (below ~3,000 HDD), actual savings could be noticeably less than the estimate.
Fuel costs vary significantly by region and over time. For natural gas enter cost per therm, for electricity per kWh, and for fuel oil or propane per gallon. Contact your local utility or fuel provider for current rates, or check the U.S. Energy Information Administration (EIA) website for average regional prices.
The U.S. Department of Energy recommends R-38 to R-60 for attics in most climate zones, and R-13 to R-21 for walls depending on your region. In colder climates (higher HDD), higher R-values have a better return on investment. The EnergyStar Insulation Map is a helpful reference.
The CO₂ estimate is based on the BTUs of fuel saved per year and the emissions factor for each fuel type. Natural gas produces about 117 lbs of CO₂ per million BTU, electricity varies by grid mix (~1.2 lbs/kWh average), fuel oil ~161 lbs/MMBtu, and propane ~139 lbs/MMBtu.
Payback period depends on the cost of insulation installation and your annual savings. Many homeowners see a full payback in 3 to 7 years for attic insulation upgrades, after which the savings are essentially pure profit. Adding this calculator's 10-year savings to your estimate gives a good sense of the long-term value.