Home Energy Audit Calculator
A home energy audit estimates how much energy your home uses for heating, cooling, and appliances, and what it costs annually. This calculator applies the U.S. Department of Energy's standard load methodology: combining your home's floor area, the local heating and cooling degree days for your climate zone, an estimated building envelope efficiency (U-value), and your HVAC equipment efficiency ratings. Enter your home details below to get an annual energy cost breakdown. Use these results to prioritize energy upgrades such as insulation improvements, HVAC replacement, or air sealing.
Home energy audit formulas
Heating Energy (therms) = (HDD x Floor Area x 0.0012) / (AFUE / 100)
Cooling Energy (kWh) = (CDD x Floor Area x 0.25) / SEER
Heating Cost = Heating Energy x Gas Rate
Cooling Cost = Cooling Energy x Electricity Rate
The load factor 0.0012 BTU/(sq ft * degree day) and 0.25 BTU/(sq ft * degree day) for cooling are derived from DOE Building Energy Data Book residential sector averages. One therm equals 100,000 BTU. Adjust these inputs for your actual insulation level: better-insulated homes use lower effective load factors.
How to interpret your results
- If heating costs dominate, prioritize insulation upgrades (attic, walls) and air sealing to reduce heat loss.
- If cooling costs are high, consider a higher SEER air conditioner, ceiling fans, and window shading to reduce cooling loads.
- The EPA Energy Star program estimates that properly air-sealing and insulating a home can save an average of 15% on total energy costs.
- Upgrading from an 80% AFUE to a 95% AFUE furnace saves roughly 18% on heating fuel costs alone.
- For a certified energy audit with blower door testing and thermal imaging, contact a BPI or RESNET-certified energy auditor.
Home energy audit calculator: frequently asked questions
What is a home energy audit calculator?
A home energy audit calculator estimates your annual home energy consumption and cost by combining your home's square footage, heating and cooling equipment efficiency, local climate data, and utility rates. It helps identify where energy is being wasted.
How accurate is this estimate?
This calculator uses DOE standard load factors and average efficiency assumptions. Actual energy use varies by occupant behavior, local climate, equipment age, and insulation quality. For a certified audit, contact a BPI or RESNET-certified auditor.
What is the DOE formula for heating energy use?
The DOE uses: Heating Energy (MMBtu) = (Heating Degree Days x Floor Area x U-value) / Furnace Efficiency. The U-value represents the overall thermal conductance of the building envelope, and Heating Degree Days come from NOAA climate data for your location.
What insulation level should I target?
The DOE recommends R-38 to R-60 attic insulation in most US climate zones, R-13 to R-21 for walls, and R-25 to R-30 for floors over unconditioned spaces. Higher R-values are recommended for colder climates (zones 5-8).
How do I reduce my home energy costs?
The EPA Energy Star program recommends: sealing air leaks (saves up to 20% on heating and cooling), adding insulation, upgrading to high-efficiency HVAC (SEER 18+ for AC, AFUE 95+ for furnaces), installing a programmable thermostat, and using Energy Star appliances.
Official sources
- U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy: Home Energy Audits.
- U.S. Energy Information Administration: Use of Energy in Homes.
- EPA Energy Star: Seal and Insulate with Energy Star.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.