What is the difference between SEER and EER?

SEER (Seasonal Energy Efficiency Ratio) is the total cooling output divided by the total electrical energy consumed over a typical cooling season, accounting for varying outdoor temperatures. EER (Energy Efficiency Ratio) is a snapshot: cooling capacity at exactly 95°F outdoor / 80°F indoor / 50% RH divided by power at that same condition. SEER is higher than EER for the same unit because seasonal conditions average out to milder temperatures than the EER test point.

What conversion factor does this tool use?

The tool uses EER = SEER × 0.875, which is the widely cited approximation from ASHRAE and ARI/AHRI. The exact factor ranges from about 0.85 (hot desert climates) to 0.90 (milder climates) because it depends on the local bin-temperature distribution. For most U.S. regions the 0.875 midpoint is a good engineering approximation.

What is a good SEER rating for a central air conditioner?

The current federal minimum is SEER 14 in most U.S. states (SEER 15 in the Southeast and Southwest as of 2023 standards). ENERGY STAR units start at SEER 15–16. High-efficiency variable-speed systems reach SEER 20–26. For most homeowners, SEER 16–18 offers a good balance of upfront cost and long-term savings.

What is a good EER rating for a window air conditioner?

Window and room air conditioners are rated in EER. The federal minimum is EER 9.7–12 depending on capacity. ENERGY STAR units are typically EER 12 or higher. A high-efficiency unit can reach EER 14–15. In very hot climates where the unit runs near peak load often, EER is more representative of real energy use than SEER.

Does a higher SEER always mean lower electricity bills?

Higher SEER lowers energy consumption per unit of cooling, but total bill depends on how many hours the system runs, the local electricity rate, and the size of your home. This tool estimates annual cost using average run-hours by climate zone — your actual usage may differ. Proper sizing and duct sealing often reduce bills more than a SEER upgrade alone.

SEER to EER Converter

Enter a SEER or EER rating to convert between the two efficiency metrics and see estimated annual cooling costs.

Efficiency Conversion

Convert from

SEER → EER EER → SEER

SEER Rating

Typical range: SEER 13–26 for central AC

Optional — Annual Cost Estimate

System Capacity (tons)

1 ton = 12,000 BTU/h. Leave blank to skip cost estimate.

Electricity Rate (¢/kWh)

U.S. average is about 16 ¢/kWh (2024).

Climate Zone

Results

Enter a rating and click Convert

Summary

SEER (Seasonal Energy Efficiency Ratio) measures average cooling efficiency over an entire season; EER (Energy Efficiency Ratio) measures efficiency at a single peak-load test condition (95°F outdoor, 80°F indoor, 50% RH). The industry-standard conversion formula is EER ≈ SEER × 0.875 in most climates, though the exact factor ranges from 0.85 to 0.90 depending on bin-temperature distribution. This tool converts in both directions and optionally estimates annual electricity cost based on system size and local electricity rate.

How it works

Choose whether you want to convert from SEER to EER or from EER to SEER.
Enter the efficiency rating printed on the equipment nameplate or in the spec sheet.
The tool applies the standard conversion factor (SEER × 0.875 = EER) to compute the result.
Optionally enter system size (tons or BTU/h) and your electricity rate to see estimated annual cost.
Review the result alongside the minimum federal efficiency standards for context.

Use cases

Compare an older EER-rated window unit against a new central system rated in SEER.
Estimate annual electricity cost before purchasing a new air conditioner.
Convert equipment specs when a manufacturer lists only one rating.
Verify whether a system meets the current federal minimum SEER or EER standard.
Calculate payback period when upgrading from a lower to a higher efficiency unit.
Help customers understand the difference between seasonal and peak efficiency.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu