Enter the cooling capacity in BTU per hour, the annual full-load operating hours for your climate, the SEER ratings of the old and new systems and your electricity rate per kilowatt-hour. Use equivalent full-load cooling hours derived from the building’s cooling load and equipment capacity; clock hours with the fan running are not equivalent full-load hours. SEER, the seasonal energy efficiency ratio, is the cooling delivered per watt-hour of electricity.
Find the old rating on the nameplate, and note that newer ratings use SEER2, a more realistic test standard.
Use efficiency ratings on the same test basis. SEER and SEER2 are different procedures and the calculator does not supply a universal conversion between them. Equivalent full-load hours are an assumption, not raw thermostat-on hours.
Actual loads, ducts, controls and installation affect costs. This model excludes installed price, heating energy and any current incentive eligibility.
Estimated annual savings from cooling capacity
| Cooling capacity | 36,000 |
|---|---|
| Annual full-load hours | 1,000 |
| Old system SEER | 10 |
| New system SEER | 16 |
| Electricity rate | $0.15 |
| Estimated annual savings | $203 |
| New system annual operating cost | $338 |
Common error: Counting on the full saving from a rating alone. Duct leaks, poor installation and an incorrectly sized unit can waste much of the gain.
SEER Upgrade Savings: formula
ASHRAE Handbook; Fundamentals · DOE: Central AC and heat-pump test procedure
SEER Upgrade Savings: changing Electricity rate
| Electricity rate | Estimated annual savings | New system annual operating cost |
|---|---|---|
| $0.12 | $162 | $270 |
| $0.14 | $189 | $315 |
| $0.15 (example) | $203 | $338 |
| $0.17 | $230 | $383 |
| $0.18 | $243 | $405 |
SEER Upgrade Savings: compare input ranges
| Input | Tested from | To | Estimated annual savings: low input | Estimated annual savings: high input | Swing |
|---|---|---|---|---|---|
| Old system SEER | 9 | 11 | $263 | $153 | $109 (54%) |
| New system SEER | 14 | 18 | $154 | $240 | $86 (42%) |
| Cooling capacity | 32,400 | 39,600 | $182 | $223 | $41 (20%) |
| Annual full-load hours | 900 | 1,100 | $182 | $223 | $41 (20%) |
| Electricity rate | $0.14 | $0.17 | $189 | $230 | $41 (20%) |
SEER Upgrade Savings: individual input comparisons
| Input | Value | Estimated annual savings | New system annual operating cost |
|---|---|---|---|
| Cooling capacity | 28,800 | $162 | $270 |
| 32,400 | $182 | $304 | |
| 36,000 | $203 | $338 | |
| 39,600 | $223 | $371 | |
| 43,200 | $243 | $405 | |
| Annual full-load hours | 800 | $162 | $270 |
| 900 | $182 | $304 | |
| 1,000 | $203 | $338 | |
| 1,100 | $223 | $371 | |
| 1,200 | $243 | $405 | |
| Old system SEER | 8 | $338 | $338 |
| 9 | $263 | $338 | |
| 10 | $203 | $338 | |
| 11 | $153 | $338 | |
| 12 | $113 | $338 | |
| New system SEER | 13 | $125 | $415 |
| 14 | $154 | $386 | |
| 16 | $203 | $338 | |
| 18 | $240 | $300 | |
| 19 | $256 | $284 | |
| Electricity rate | $0.12 | $162 | $270 |
| $0.14 | $189 | $315 | |
| $0.15 | $203 | $338 | |
| $0.17 | $230 | $383 | |
| $0.18 | $243 | $405 |
Estimated annual savings: Electricity rate against Cooling capacity
| Electricity rate / Cooling capacity | 28,800 | 36,000 | 43,200 |
|---|---|---|---|
| $0.12 | $130 | $162 | $194 |
| $0.14 | $151 | $189 | $227 |
| $0.15 | $162 | $203 | $243 |
| $0.17 | $184 | $230 | $275 |
| $0.18 | $194 | $243 | $292 |
SEER Upgrade Savings: values and definitions
| Quantity and definition | Value used |
|---|---|
| Cooling capacity — Rated cooling capacity, in BTU per hour. | 36,000 |
| Annual full-load hours — Estimated equivalent full-load cooling hours per year. | 1,000 |
| Old system SEER — SEER rating of the existing system. | 10 |
| New system SEER — SEER rating of the replacement system. | 16 |
| Electricity rate — Cost per kilowatt-hour of electricity. | $0.15 |
| Estimated annual savings | $203 |
| New system annual operating cost | $338 |
The SEER rating measures cooling output per unit of electricity, so a higher rating uses less power for the same cooling. A 3-ton system running 1,000 full-load hours a year uses about 3,600 kilowatt-hours at SEER 10 and about 2,250 at SEER 16. At 15 cents a unit, that is a saving of about $203 a year, with the new system costing about $338 a year to run.
The saving rises with hotter climates, longer cooling seasons and higher electricity prices.
Use your own full-load hours and your electricity rate, and compare the yearly saving with the installed cost. The payback is often longer than the saving suggests.
Size the system on the HVAC tonnage calculator, check ducts on the duct sizing and static pressure pages and see local climate on the degree days calculator. The energy and power converters change units, and the loan calculators compare financing costs.
What produces $202.50 annual savings?
At 36,000 Btu/h and 1,000 equivalent full-load hours, SEER 10 uses 3,600 kWh and SEER 16 uses 2,250 kWh. At $0.15/kWh, the difference is $202.50.
Can an old SEER number be compared directly with a SEER2 number?
They use different testing procedures. Obtain ratings on a comparable basis or an appropriate model-specific comparison before treating the ratio as energy savings.
Does the result establish an economical replacement?
No. The calculation excludes installed cost, maintenance, remaining service life, financing and the actual future electricity tariff.