WattThe?!
Back to
tools

HVAC Energy Cost Calculator: Heating & Cooling Cost Per Hour, Day, Month

Heating and cooling is typically the single largest item on a home electricity bill — often 40–50% of annual usage. The two knobs that matter most are efficiency (SEER rating) and runtime. A 15-SEER central AC draws about 40% less power than a 10-SEER unit of the same size, and every hour you can trim from daily runtime is an hour you don't pay for. Enter your system specs and local rate below to see exactly what your HVAC costs to run.

System type
System size(tons)
SEER / efficiency rating
Runtime 8hours/day
State (auto-fills rate)
Electricity rate($/kWh)
Power draw
2.40kW

36.0 kBTU/hr ÷ SEER 15

Cost per hour
$0.41

2.40 kW × $0.170/kWh

Cost per day
$3.26

8 hrs × 2.40 kW

Cost per month
$97.92

30 days at 8 hrs/day

Cost per season
$391.68

120 days at 8 hrs/day

Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.

How we calculate this →

How HVAC electricity cost is calculated

The core formula converts system capacity (tons) and efficiency (SEER) into power draw in kilowatts. One ton of cooling = 12,000 BTU per hour. Dividing by SEER gives watts of electricity needed to deliver that cooling — for example, a 3-ton / 15-SEER central AC draws (3 × 12,000) ÷ (15 × 1,000) = 2.4 kW. Multiply by runtime to get daily kWh, then by your rate.

SEER (Seasonal Energy Efficiency Ratio) is the key efficiency lever. A 10-SEER system draws 3.6 kW for the same 3-ton output — 50% more power than a 15-SEER unit. Over a 120-day cooling season at 8 hours/day and $0.17/kWh, that gap costs roughly $200. Modern high-efficiency units rated 20+ SEER can cut that further.

Runtime is the other dial you can actually control. Raising the thermostat set point a few degrees, using programmable or smart thermostats to reduce runtime during unoccupied hours, and improving envelope insulation (sealing air leaks, adding attic insulation) all reduce daily runtime — typically by more than swapping equipment.

Frequently asked questions

A typical 3-ton central AC with a 15 SEER rating running 8 hours a day at the US average rate of $0.17/kWh costs roughly $98 per month. At $0.13/kWh it drops to about $75; at $0.25/kWh it rises to around $148. The biggest variables are local electricity rates, how many hours per day the system actually runs (which depends on outdoor temperature, thermostat set points, and insulation quality), and system efficiency.

Yes — proportionally. A 20-SEER system draws exactly 33% less electricity than a 15-SEER system of the same size, because SEER is a direct efficiency ratio: higher SEER means fewer watts to deliver the same BTU/hr of cooling. Upgrading from a 10-SEER to a 20-SEER system cuts cooling electricity use in half. The payback period depends on how many hours per year you run the system; in hot climates with long cooling seasons, higher-SEER equipment pays back quickly. The federal minimum for new central AC in most of the US is now 14 or 15 SEER depending on region.

A heat pump in heating mode is significantly cheaper to run than an electric resistance furnace because it moves heat rather than generating it. A heat pump with a COP (Coefficient of Performance) of 2.5 uses 2.5x less electricity than an electric furnace delivering the same heat output. In mild climates (above ~35°F), a modern heat pump typically runs at COP 2.5–3.5 in heating mode, cutting heating costs by 60–70% versus electric resistance. Gas furnaces compare differently — cost depends entirely on the local gas-to-electricity price ratio, but heat pumps are increasingly cost-competitive even against gas as efficiency improves.

Related calculators

Air Conditioner Electricity Cost CalculatorSpace Heater Electricity Cost CalculatorAppliance Electricity Usage Calculator