Every air conditioner gets a score from 0 to 100% built from five factors, which maps onto the 5-point rating shown on the site (a 0% score would be 1.5 stars; a perfect score, 5). Each factor is scored against fixed reference points, not against the other products in the list, so adding a new model never moves another model’s rating. Window and portable units are ranked separately, each on its own scale.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per 1,000 BTU of certified cooling | 30% |
| Efficiency | certified CEER | 30% |
| Quiet | sound on the lowest fan speed | 15% |
| Inverter & app | variable-speed compressor and Wi-Fi app | 15% |
| Warranty | whole-unit warranty length | 10% |
Where the numbers come from
Every room air conditioner sold in the US must be tested to a Department of Energy procedure and certified. We take capacity and efficiency from the ENERGY STAR certified room air conditioner list and the DOE Compliance Certification Database, which also covers models that aren’t ENERGY STAR.
Window units are rated on cooling capacity in BTU per hour at standard conditions.
Portable units are rated on seasonally adjusted cooling capacity (SACC). It averages performance at 95 °F and 83 °F and counts the heat that leaks back in through the case and the warm air drawn into the room to replace what the exhaust hose blows out. It is usually 30 to 50% lower than the ASHRAE rating printed large on the box, which ignores those losses. The ASHRAE figure is shown on each product page for reference but never used.
CEER (combined energy efficiency ratio) is BTU of cooling per watt-hour of electricity, including standby power. Portables are tested in a way that counts their losses, so their CEERs are much lower than window units’ and the two are scored on separate scales.
Noise, features and warranty come from the maker’s spec sheet, manual or warranty document.
The factors
Value is the price divided by certified capacity: dollars per 1,000 BTU.
| Type | Scores 0 | Full marks |
|---|---|---|
| Window | $80 per 1,000 BTU | $25 per 1,000 BTU |
| Portable | $90 per 1,000 BTU (SACC) | $30 per 1,000 BTU (SACC) |
Efficiency is the certified CEER.
| Type | Scores 0 | Full marks |
|---|---|---|
| Window | CEER 11 | CEER 16.5 |
| Portable | CEER 6 | CEER 15 |
An 8,000 BTU window unit at CEER 15 running 8 hours a day for a 100-day summer uses about 430 kWh; at CEER 11, about 580.
Quiet is the maker’s indoor sound rating on the lowest fan speed, where an air conditioner spends most of a night: 58 dB(A) scores zero and 40 dB(A) full marks. Makers measure at different distances, so treat it as a guide; the high-speed figure is shown on each product page.
Inverter & app: an inverter (variable-speed) compressor scores 60% of the factor and a Wi-Fi app the other 40%. An inverter ramps down as the room cools instead of switching on and off, so it holds the temperature steadier, runs quieter and usually earns a higher CEER. An app lets you start cooling before you get home and set schedules.
Warranty is the whole-unit parts-and-labor warranty: 1 year scores zero and 5 years full marks. Many makers cover the compressor and sealed system for longer; that’s shown on the product page but not scored, since the parts most likely to fail early (fans, boards, sensors) fall under the whole-unit term.
What isn’t scored
Heat mode, dehumidifying, voice assistants, refrigerant type, weight and window fit are listed but not scored. Heat is a filter on its own page, air conditioners with heat. Independent tests are listed where they exist, but there are too few to score.
Missing data
If a figure isn’t published, that factor gets the neutral middle score (50) and the product page marks it as estimated.
Ties and discontinued models
Products are ranked by score within each type. Discontinued models stay listed but rank below every current model and can be hidden with the “Hide discontinued” filter.