CEER (Combined Energy Efficiency Ratio) is the efficiency metric for window and portable air conditioners that accounts for both active cooling efficiency and standby power consumption. It replaced the standard EER for room ACs in 2014 because window units draw measurable electricity even when they're plugged in but not actively cooling. A good CEER for a typical 8,000-12,000 BTU window AC is 12.0 or higher, which meets ENERGY STAR certification.
If you're shopping for a window AC, CEER is the number on the EnergyGuide label. Higher CEER means lower electricity bills over the cooling season.
The CEER Formula
CEER = Cooling Capacity (BTU/h) / (Active Power (W) + Standby Power Adjustment (W))
The standby power adjustment accounts for electricity consumed when the unit is in off mode or standby mode (plugged in but compressor not running). The DOE formula weights active and standby power based on assumed annual hours in each mode.
In practice, CEER is slightly lower than EER for the same unit because standby power adds to the denominator. For a unit with 800W active power and 2W standby, the CEER might be 0.1-0.3 points lower than the EER.
Standby power is small but adds up. A window AC drawing 2 watts in standby for 6,000 hours per year (the hours it's not actively cooling) uses 12 kWh — about $2 per year. For larger units with digital controls and WiFi, standby draw can reach 5-10W, adding $5-$10 annually. CEER captures this cost that EER missed.
CEER Requirements by Capacity
Federal minimum CEER varies by the unit's cooling capacity. Smaller units must meet higher CEER minimums because their compressors are proportionally less efficient:
Window ACs with louvered sides have slightly different minimums because the louvered design allows more outdoor air to cool the condenser. Check the specific category for your unit type on the ENERGY STAR product finder.
What's a Good CEER for a Window AC?
CEER vs EER: What Changed
The difference between EER and CEER is small for most units (0.1-0.3 points) because standby power is typically only 1-10W compared to 500-1,500W of active cooling power. But across millions of installed window ACs, the standby draw adds up to significant national energy consumption.
Top Window ACs by CEER (2026)
Inverter window ACs dominate the high-CEER charts because they modulate compressor speed based on demand, similar to how variable-speed central ACs achieve high SEER2. The Midea U-Shaped inverter series consistently leads in both CEER and noise performance.
Calculating Window AC Operating Costs
Annual Cost = (BTU/h / CEER) x Annual Cooling Hours x ($/kWh / 1,000)
Example: An 8,000 BTU window AC with 12.1 CEER running 1,000 hours at $0.16/kWh.
Power draw = 8,000 / 12.1 = 661 watts
Annual kWh = 661 x 1,000 / 1,000 = 661 kWh
Annual cost = 661 x $0.16 = $106
The same unit at 10.0 CEER: 800W, 800 kWh, $128/year. The higher CEER saves $22/year.
Window AC vs Central AC Efficiency
It's tempting to compare window AC CEER to central AC SEER2, but they measure different things:
After accounting for duct losses, a 12 CEER window unit and a 16 SEER2 central system deliver similar actual efficiency to the rooms they serve. The central system's advantage is whole-home coverage and better comfort control.
Portable AC CEER Considerations
Portable air conditioners also carry CEER ratings, but their real-world efficiency is significantly lower than window units for two reasons:
Single-hose portable ACs create negative pressure that pulls warm outdoor air into the room through gaps around doors and windows. This "infiltration load" isn't captured by CEER testing. Dual-hose models partially solve this problem but are less common.
The exhaust hose itself radiates heat back into the room. A 4-5 inch exhaust hose running at 120-140 degrees F through a room adds a measurable heat load.
A portable AC rated at 10 CEER may deliver effective cooling equivalent to only 6-7 CEER once infiltration and hose losses are factored in.
If you have the option, choose a window AC over a portable AC. Window units are consistently 30-50% more efficient in real-world use due to the inherent design advantages of sealing against the window frame and rejecting heat directly outdoors.
Key Takeaways
- CEER = cooling BTU/h divided by (active watts + standby watts). It replaced EER for window/portable ACs in 2014.
- Good CEER for most window ACs: 12.0+ (ENERGY STAR level). Premium inverter models reach 14-15.
- CEER is typically 0.1-0.3 points lower than EER for the same unit due to standby power inclusion.
- Federal minimums range from 8.5 to 11.0 CEER depending on unit capacity (smaller units have higher minimums).
- Inverter window ACs (Midea U-Shaped, LG Dual Inverter) lead in CEER and noise performance.
- Don't compare CEER to SEER2 directly — they measure different things under different conditions.
- Portable ACs have misleadingly high CEER — real-world efficiency is 30-50% lower due to hose and infiltration losses.
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