Home Energy Calculators
Estimate HVAC size, heating loads, appliance and water heating costs, solar systems and EV charging using your own rates and assumptions — every assumption is shown.
Most used
- Appliance Energy Cost CalculatorkWh and cost per day, month and year for any appliance.
- EV Charging Cost & Time CalculatorCost and time to charge an electric vehicle at home.
- Heat Pump vs Gas Furnace Cost CalculatorCompare annual heating cost of a heat pump and a gas furnace from your rates and efficiencies.
- AC BTU Calculator (Room Cooling)Room air conditioner or mini-split size in BTU/h using the ENERGY STAR room sizing method.
- Solar Panel & System Size CalculatorSolar system size (kW), number of panels, roof area and estimated yearly production.
HVAC
- BTU to kW & Tons ConverterConvert heating and cooling capacity between BTU/h, watts, kW and tons.
- CFM & Air Changes per Hour CalculatorConvert between room airflow (CFM) and air changes per hour (ACH).
- Duct Size Calculator (Velocity Method)Round duct diameter and rectangular duct size for an airflow and target velocity.
- Heating Load & Furnace Size EstimateDesign heating load from walls, windows, ceiling and air leakage; furnace input size from AFUE.
- AC BTU Calculator (Room Cooling)Room air conditioner or mini-split size in BTU/h using the ENERGY STAR room sizing method.
Heat pumps
Energy bills
Solar
- Solar Battery Size CalculatorBattery capacity (kWh) for backup days, depth of discharge and efficiency.
- Solar Payback & Savings CalculatorNet cost, payback year and lifetime savings for a solar system with your own rates and incentives.
- Solar Panel & System Size CalculatorSolar system size (kW), number of panels, roof area and estimated yearly production.
EV charging
Guides
Questions
Why do results depend so much on my utility rate?
Energy cost is energy times price. Use the all-in rate from your bill (total charges ÷ kWh or therms) for realistic results.
Can I size a whole-house HVAC system here?
You can get a preliminary estimate. Final equipment sizing should use an ACCA Manual J load calculation.