SEER2 Savings Calculator: Old AC vs a More Efficient System

A higher SEER2 rating means a central air conditioner or heat pump uses less electricity for the same cooling. But a more efficient unit also costs more. This SEER2 savings calculator shows what the efficiency gain is worth in your climate and at your electricity price.

How the calculation works

SEER2 is cooling delivered (in BTU) per watt-hour of electricity over a season. So the electricity a system uses is the cooling it delivers divided by its SEER2.

Capacity (BTU/h)     = tons × 12,000
Seasonal cooling     = capacity × full-load hours
kWh used             = seasonal cooling ÷ (SEER2 × 1,000)
Cooling cost         = kWh used × electricity price
Yearly savings       = cost with old SEER2 − cost with new SEER2
Payback (years)      = extra cost of efficient model ÷ yearly savings

One ton of cooling is 12,000 BTU per hour. Dividing by 1,000 turns watt-hours into kWh.

The default price is $0.18 per kWh, from the July 2026 US average residential price of 18.31 cents (EIA, Table 5.6.A). The default 1,200 full-load hours is a mid-range assumption, not a measured value for your area.

The calculator assumes both systems deliver the same cooling over the same hours, and that each one performs at its rated SEER2. Real performance depends on installation, ducts and refrigerant charge.

Worked example

The default inputs: a 3-ton system, 1,200 full-load cooling hours, an old system at 10 SEER2, a new one at 16 SEER2, and $0.18 per kWh.

1. Seasonal cooling: 3 × 12,000 × 1,200 = 43.2 million BTU.
2. Old system: 43,200,000 ÷ (10 × 1,000) = 4,320 kWh, costing about $778 a year.
3. New system: 43,200,000 ÷ (16 × 1,000) = 2,700 kWh, costing about $486 a year.
4. Savings: about $292 a year and 1,620 kWh.

The default extra cost is $0, so the payback line reads “No extra cost entered”. Add the price difference between the two models to see a real payback.

A second example

A household in a hot climate has a 2.5-ton system rated 13 SEER2 and runs it about 2,000 full-load hours a year. They pay $0.155 per kWh. A 17 SEER2 replacement costs $1,500 more than a minimum-efficiency model. The calculator shows cooling costs falling from about $715 to $547 a year, a saving of about $168 and 1,086 kWh, and a payback on the extra cost of about 8.9 years.

What your result means

Yearly savings is what the efficiency gap is worth each cooling season at today’s price. Payback compares that with the extra price of the efficient model, not the whole system.

If you must replace a broken system anyway, compare models you could actually buy. The question is not “should I replace?” but “is the more efficient choice worth the extra cost?” A payback well inside the system’s expected life is a good sign. A payback longer than the life of the system usually is not, unless comfort features such as variable speed or better humidity control matter to you.

If your current system works, a big SEER2 jump alone rarely justifies replacing it early. Run the full project cost through the energy upgrade payback calculator to check.

How climate and SEER2 change the savings

Using the calculator’s defaults (3 tons, old system 10 SEER2, $0.18 per kWh):

Notice that each step up in SEER2 saves a bit less than the step before. Going from 10 to 14.3 saves far more than going from 18 to 20. Hours of use matter as much as the rating.

Standards, incentives and local factors

Federal minimums. Since January 1, 2023, DOE requires split-system central air conditioners under 45,000 BTU per hour to reach 13.4 SEER2 in the North and 14.3 SEER2 in the Southeast and Southwest; split-system heat pumps must reach 14.3 SEER2 everywhere (DOE FAQ). DOE’s regional enforcement guidance says units that do not meet the regional standard cannot be installed in the Southeast or Southwest.

Tax credits. The federal 25C credit does not apply to property placed in service after December 31, 2025 (IRS). There is no federal tax credit for a new AC or heat pump installed in 2026. See our 2026 energy tax credit guide.

Rebates. State Home Energy Rebate programs run only in some states, and since DOE Program Notice 26-2 (effective May 29, 2026) heat pump rebates are limited to homes that already heat with electricity or new construction. Utility rebates vary. Check our rebates by state guide and DSIRE.

Electricity prices. In July 2026, average residential prices ranged from about 12.72 cents per kWh in Louisiana to 48.00 cents in Hawaii (EIA). The same efficiency upgrade is worth almost four times as much at the high end.

Common mistakes

• Mixing SEER and SEER2. An old unit’s SEER label and a new unit’s SEER2 label are not the same scale. Convert the old one down slightly.
• Using total run hours instead of full-load hours. Systems often run at part load, so full-load hours are lower than the hours the fan is on.
• Counting the whole system price as “extra cost.” If you must replace the unit anyway, only the price difference between models belongs in the payback.
• Ignoring installation quality. Leaky ducts, wrong refrigerant charge or poor airflow can erase the rated efficiency.
• Oversizing. A system that is too big short-cycles. Ask for a Manual J load calculation, and see our heat pump cost and savings guide.

Limits of this calculator

The calculator uses rated SEER2 values and one average electricity price. It does not model part-load behavior, duct losses, humidity removal, time-of-use rates, aging equipment or future price changes. It covers cooling only, not heating.

It gives an educational estimate, not a quote or advice. Get at least three written quotes that list each model’s SEER2 rating and AHRI certificate number.