Buying guide
Window AC Buying Guide (2026)
How to buy a window air conditioner: BTU sizing math, CEER efficiency, noise ratings, and installation requirements.
Step 1: Size by BTU using the 20-per-square-foot rule
Multiply your room's square footage by 20 for a baseline: a 250 sq ft room needs ~5,000-6,000 BTU, 350 sq ft needs 8,000, 550 sq ft needs 12,000, and 800 sq ft needs 14,000. Then adjust: add 10% for high ceilings or heavy western sun, add for kitchens (heat from appliances), subtract slightly for heavily shaded, well-insulated rooms. The cardinal rule: oversizing is worse than undersizing. An oversized unit cools the air in minutes and shuts off before dehumidifying, leaving the room cold and clammy. An undersized unit runs constantly but at least dehumidifies.
Step 2: Read CEER like a price tag on future summers
CEER (Combined Energy Efficiency Ratio) tells you cooling per watt. The spread in this guide runs from 11.0 (GE) to 15.0 (Midea U). Every point of CEER is roughly 8-9% less electricity for the same cooling. Multiply that by your hours of use and summers of ownership: a daily-use bedroom unit repays an efficiency premium in 2-4 seasons. Check Energy Star certification as a verified floor; uncertified units cluster at the bottom of the efficiency range.
Step 3: Treat decibels as a sleep decision
Window AC noise is dominated by compressor type. Conventional rotary compressors (Frigidaire, GE) cycle on and off audibly in the mid-50s dB. Inverter compressors (LG, Midea) hum continuously at lower levels, 42-44 dB in sleep modes, with no restart thump. The decibel scale is logarithmic: 42 vs 55 dB is perceived as roughly half the loudness. For bedrooms, this single spec outweighs most feature differences; for rarely used guest rooms, it barely matters.
Buy this type if / avoid if: the decision framework
Buy an inverter unit (LG, Midea U) if: the AC runs daily through summer, the room is a bedroom or office where noise matters, or you will own it 5+ years (efficiency payback). Buy a conventional Energy Star unit (Frigidaire) if: the room is a standard bedroom, budget is real, and normal AC hum is acceptable. Buy the budget unit (GE) if: the room is genuinely under 250 sq ft and every dollar counts. Avoid oversizing if: your room is small; a 14,000 BTU unit in a 300 sq ft bedroom short-cycles into clamminess. Avoid the Midea U if: your window is not a compatible double-hung type. Avoid extension cords always: plug every window AC directly into the wall.
Questions, answered
Do I need a support bracket?
For units over 80 pounds or installations above the ground floor, yes. The bracket transfers weight to the wall instead of the window sash. The Midea U includes its saddle bracket; the LG 14,000 BTU needs a separate support bracket, which is not optional at its weight.
Can I install a window AC myself?
Units up to 12,000 BTU are DIY-able for one careful person; the GE 6,000 is the easiest. The LG 14,000 BTU needs two people. The Midea U needs one person comfortable with bracket assembly. If your window is above ground level, get help regardless of unit size.
Should I remove the AC in winter?
Ideally yes, or at minimum cover it. An installed unit leaks heated air around its edges all winter and exposes the seals to freeze-thaw. An insulated cover is the minimum; removal and storage is the best practice.
Why is my AC icing up?
Three usual causes in order: a dirty filter restricting airflow (clean it), low refrigerant from a leak (needs service), or running the unit when outdoor temperatures drop below about 60°F. Icing on a new unit with a clean filter in normal weather means a defect; contact the manufacturer.