Energy Cost Calculator
Estimate energy cost from watts or kWh, or estimate HVAC operating cost from BTU/h using SEER/EER (cooling) and COP/HSPF/AFUE (heating). Supports electric, natural gas, propane, and heating oil.
Updated for 2026 SEER2 standards and current energy rates.
On this page: Calculator · Common costs · Tips · FAQ
Need to size equipment first? Use the advanced BTU calculator or AC size calculator, then come back here to estimate costs. To compare SEER upgrades, use the SEER savings calculator.
Fast way to estimate cost
If you know the device watts, enter watts + hours/day + your rate. If you're comparing HVAC systems, enter BTU/h plus efficiency and runtime. US average electricity rate is about $0.16/kWh — find your local rate.
For sizing equipment first, run the advanced BTU calculator and then compare costs here. For a code-compliant load calculation, get an HVAC quote with a Manual J.
Typical HVAC operating costs
Rough monthly estimates for common equipment running 8 hours/day at $0.16/kWh electricity. Your actual costs depend on runtime, efficiency, and local rates.
| Equipment | Typical watts | Est. monthly cost | Sizing tool |
|---|---|---|---|
| Window AC (5,000 BTU) | ~450 W | $17–$22 | Window AC calc |
| Window AC (10,000 BTU) | ~900 W | $35–$45 | Window AC calc |
| Portable AC (12,000 BTU) | ~1,100 W | $42–$55 | Portable AC calc |
| Central AC (3 ton, 14 SEER) | ~2,600 W | $100–$130 | AC size calc |
| Mini split (12,000 BTU) | ~600 W | $23–$30 | Mini split calc |
| Space heater (1,500 W) | 1,500 W | $58–$65 | Space heater calc |
| Heat pump (3 ton, COP 3.0) | ~3,500 W | $135–$170 | Heat pump calc |
| Ceiling fan (52″) | ~60 W | $2–$3 | Ceiling fan calc |
Track actual usage with a Kill A Watt energy monitor ($20–30). Find your local rate at ElectricityLocal.
Tips for a more realistic estimate
Runtime matters most — reducing hours per day has a bigger impact than upgrading efficiency by a point or two. A smart thermostat ($25–250) reduces runtime 10–15% automatically with scheduling and geofencing.
Efficiency varies with conditions — real-world SEER is lower than rated SEER on extremely hot days. Dirty filters, leaky ducts, and poor insulation all reduce effective efficiency. Check your air filter size and replace on schedule (shop filters).
Compare upgrades — the SEER savings calculator shows exactly how much a higher-efficiency unit saves per year. The heat pump calculator and furnace size calculator help compare heating options.
Helpful tools: energy monitor ($20–30) · local rate lookup · weatherstripping ($5–15) · window insulation ($10–30).
Reduce costs before you calculate them
A smart thermostat ($25–250) cuts HVAC costs 10–15% automatically. Combined with weatherstripping ($5–15) and clean air filters ($15–30), you can reduce monthly costs by 15–25% before upgrading equipment.
Check federal tax credits for high-efficiency upgrades — up to $2,000 for qualifying heat pump systems.
Frequently asked questions
How do I calculate electricity cost from watts?
Choose “Electric device,” enter watts, hours/day, and your electricity rate. The formula: kWh = (watts × hours) ÷ 1,000. Cost = kWh × $/kWh. A 1,500 W space heater running 8 hours at $0.16/kWh costs about $1.92/day or $58/month. For precise measurement, use a plug-in energy monitor.
What's the difference between SEER and EER?
SEER is a seasonal rating averaged over a full cooling season, while EER is measured at a single test condition (95°F outdoor). SEER is more common on product labels and better reflects typical annual performance. Use whichever rating you know — the calculator supports both. For comparing SEER upgrades specifically, the SEER savings calculator gives more detail.
Can I estimate heating cost for gas or propane?
Yes. Select HVAC mode, choose heating, pick your fuel (natural gas, propane, or heating oil), enter your rate, and set the system efficiency (AFUE). Standard energy content: 1 therm = 100,000 BTU, 1 gallon propane = 91,500 BTU, 1 gallon oil = 138,500 BTU. For furnace sizing, use the furnace size calculator.
What is COP vs HSPF for heat pumps?
COP (Coefficient of Performance) is the ratio of heat output to electricity input at a single condition — COP 3.0 means 3 units of heat per 1 unit of electricity. HSPF (Heating Seasonal Performance Factor) is the seasonal average in BTU per watt-hour. HSPF 9.0 ≈ COP 2.6. For heat pump sizing, use the heat pump calculator.
How do I find my electricity rate?
Check your utility bill for the per-kWh rate (often “supply” + “delivery” combined). The US average is about $0.16/kWh but ranges from $0.10 to $0.40+ by region. Look up your local rate at ElectricityLocal.