SEER2 savings calculator

How the calculator works

ENERGY STAR defines SEER2 as the total heat removed during the cooling season, in BTU, divided by the electricity used over the same season, in watt-hours (ENERGY STAR heat pump key product criteria). Turned around, that gives the electricity a system uses:

• kWh per year = capacity in BTU/h x cooling hours ÷ (SEER2 x 1,000)
• Cost per year = kWh per year x your electricity rate
• Savings = cost at the lower rating minus cost at the higher rating
• Payback = extra price of the higher-rated system ÷ yearly savings

Capacity comes from tons x 12,000 BTU/h. Cooling hours means hours at full output, so a system that cycles on and off counts only the time it actually runs at capacity.

Worked example

A 3-ton system is 36,000 BTU/h. At 1,000 full-output hours a year, a 13.4 SEER2 unit uses 36,000 x 1,000 ÷ 13,400 = 2,687 kWh. A 15.2 SEER2 unit uses 36,000 x 1,000 ÷ 15,200 = 2,368 kWh. The difference is 318 kWh, which is about $54.08 a year at $0.17 per kWh.

Picking the numbers

• Ratings: the federal minimum for split central ACs under 45,000 BTU/h is 13.4 SEER2 in the North and 14.3 SEER2 in the Southeast and Southwest, and ENERGY STAR needs 15.2 SEER2. Our guide to what a good SEER rating is lists the minimums by region and equipment type.
• Compare like with like: SEER and SEER2 use different test procedures, so do not put an older unit's SEER number next to a new unit's SEER2 number without noting that.
• Hours: the 1,000-hour default is only a starting point. Raise it for long, hot summers and lower it for mild ones.
• Rate: the $0.17 default is a placeholder. Use the price per kWh on your own bill, including delivery charges.

Limits

Real use depends on the thermostat setting, duct leaks, installation quality and weather. The math compares ratings fairly, but your bill will not match it exactly. Heating costs for a heat pump depend on HSPF2 and are not included.