What Specs to Look for When Buying an Air Conditioner? Energy Efficiency Rating, APF, and Refrigerant Type Are the Three Key Factors

Air conditioners are among the most frequently used, highest electricity-consuming home appliances. Choose wrong and you'll pay hundreds of extra kilowatt-hours per year; choose right and the electricity savings over ten years can buy you a new unit. This article helps you build a parameter framework for selecting an air conditioner.

APF: The Single Critical Number for Measuring Energy Efficiency

APF (Annual Performance Factor): The sum of total annual cooling and heating output divided by annual electricity consumption. A higher APF means less electricity consumed for the same amount of cooling/heating.

New national standards (GB 21455-2022) use APF as the sole criterion for energy efficiency rating:

Energy Rating	APF (1.5 HP model example)	Notes
Grade 1	≥ 5.0	Most energy-efficient, first choice
Grade 2	≥ 4.5	Second best choice
Grade 3	≥ 4.0	Passing threshold
Grade 4	≥ 3.5	Below average
Grade 5	≥ 3.3	Nearly obsolete in the market

Savings calculation:

For a 1.5 HP model running 1,000 hours per year
Grade 1 (APF=5.0) vs Grade 3 (APF=4.0): Annual electricity difference approximately 75 kWh; at ¥0.6/kWh, saves about ¥45 per year
¥450 savings over 10 years; the price difference between Grade 1 and Grade 3 is typically within ¥300–500, making Grade 1 a better long-term investment

Recommendation: Prioritize Grade 1 energy efficiency (APF ≥ 5.0); only choose Grade 2 if budget is extremely limited.

Inverter vs Fixed-Speed: No Longer Really a Choice

Mainstream home air conditioners are now almost entirely inverter models. Inverter air conditioners regulate compressor speed to precisely control cooling/heating output, rather than operating in just "full on" and "off" states like fixed-speed models.

Core advantages of inverter:

Maintains low power operation once the set temperature is reached; no frequent start-stop cycles; more energy-efficient for extended use
Small temperature fluctuations, better comfort (constant temperature control)
Stronger heating capability (in low-temperature environments)

Full DC inverter (more advanced): Not only the compressor uses variable frequency, but also the indoor and outdoor fans — achieving higher efficiency and quieter operation. Current Grade 1 energy efficiency models are basically all full DC inverter.

Refrigerant Type: R32 Is Now Mainstream, R410a Is Being Phased Out

Refrigerant is the "blood" of air conditioning operations; different refrigerants have different environmental impacts and performance characteristics.

Refrigerant	Global Warming Potential (GWP)	Notes
R22	1810	Banned, found in older units
R410a	2088	High GWP, being phased out
R32	675	Mainstream recommendation, low GWP, high efficiency
R290 (propane)	3	Most eco-friendly, but flammable; mainly in commercial units

Advantages of R32:

Compared to R410a, GWP reduced by approximately 68%
Better thermal conductivity, higher system efficiency, less refrigerant required for the same cooling capacity
After 2025, the vast majority of new domestic home air conditioners in China use R32

Purchasing recommendation: Prioritize models labeled with R32 refrigerant; if you see R410a, it's not necessarily unusable, but it's typically older stock with potentially outdated energy efficiency standards.

Expansion Device: Capillary Tube vs Electronic Expansion Valve

This is an internal structural difference that most consumers don't know about but matters significantly.

Capillary tube (Cap Tube): A thin copper tube with a fixed diameter; simple structure, low cost. Refrigerant flow is fixed and cannot be dynamically adjusted based on load, resulting in relatively lower efficiency.

Electronic Expansion Valve (EEV): A precision valve controlled by a stepper motor; can dynamically adjust refrigerant flow in real-time based on load. Combined with an inverter compressor, it achieves optimal system-wide efficiency.

Conclusion: High energy efficiency (Grade 1) inverter air conditioners are basically all equipped with electronic expansion valves; low-end fixed-speed models use capillary tubes. Choosing Grade 1 efficiency essentially means also choosing a better expansion device.

Capacity Selection: Bigger Is Not Better

Capacity (horsepower/BTU) selection baseline:

Bedroom (10–15 m²): 1 HP
Living room (20–30 m²): 1.5–2 HP
Living room (30–40 m²): 2–3 HP

Adjustment factors:

Top floor/west-facing rooms: Add 15–20% to cooling capacity requirement
Open loft spaces: Calculate based on actual volume, not just floor area
Older buildings without good insulation: Increase accordingly

Problems with oversized capacity: The compressor runs briefly and reaches the set temperature, then shuts off. This leads to persistently high indoor humidity (particularly troublesome in humid southern climates), a stuffy feeling, and increased start-stop energy costs.

Noise: Indoor Unit ≤ 40 dB Is the Comfortable Sleep Baseline

Air conditioner noise is typically labeled as the indoor unit's sound pressure level (dB) at low fan speed.

≤ 35 dB: Nearly imperceptible; sleep unaffected
36–40 dB: Normal-to-quiet; acceptable for most people
> 40 dB: Has some impact on sleep quality

For bedroom air conditioners, focus on the low fan speed noise value. Some models advertise "sleep mode" noise — also check the regular low fan speed value.

Heating Capacity: Low-Temperature Performance Matters

For those using air conditioning for winter heating, the minimum ambient temperature parameter is critical:

Standard condition heating: Heating output at outdoor temperature 7°C
Low-temperature heating: Heating output at outdoor -7°C or even -15°C

Some models show significantly reduced heating capacity below 0°C (only 60–70% of rated capacity). If your region sees temperatures below 0°C in winter, specifically check the low-temperature heating parameters, or choose models labeled with "low-temperature strong heating" capability.

Parameters in this article are sourced from GB 21455-2022 national mandatory standards and industry technical parameter documentation.