How Many Watts Does an Air Conditioner Use?

A typical central AC draws roughly 3,000–3,500 watts running for a 3-ton system. Smaller 1.5-ton units can draw around 1,400–1,700 watts, while large 5-ton systems may pull 4,700–5,800 watts. Actual draw depends on the system's SEER2 rating, age, refrigerant charge, outdoor temperature, and how hard the system is working to cool the home.

A commonly cited rule of thumb is roughly 1,000–1,200 watts per ton of cooling capacity for a central AC system running at full load. A 3-ton system would therefore draw approximately 3,000–3,600 watts running. More efficient systems (higher SEER2) draw fewer watts per ton at steady state, while older or less efficient systems may draw more.

A 2-ton central AC (24,000 BTU/hr) typically draws about 1,900–2,300 watts while running. That follows the same rule of thumb used throughout this page — roughly 1,000–1,200 watts per ton of cooling capacity at full load, so 2 tons works out to roughly 2,000–2,400 W. A newer, higher-SEER2 system tends toward the lower end of that range, while an older or less efficient unit draws toward the higher end. Starting (surge) wattage can briefly reach 2–3× the running figure when the compressor first kicks on, which matters for generator sizing. For your exact draw, check the rated amperage on the outdoor unit's nameplate and multiply by your supply voltage (typically 240 V).

A 3.5-ton central AC (42,000 BTU/hr) typically draws about 3,300–4,000 watts while running. The table above reflects typical 14–16 SEER2 systems; the simpler 1,000–1,200 watts-per-ton rule of thumb used across this page gives 3,500–4,200 W, which is where older or less efficient 3.5-ton units tend to land. Where your system falls in that range depends mainly on its SEER2 efficiency rating, age, refrigerant charge, and outdoor temperature. A higher-SEER2 system draws fewer watts per ton; an older unit may draw more. Remember that starting (surge) wattage can briefly run 2–3× higher than the running figure during compressor startup — important if you are sizing a generator. For the most accurate number, read the rated amperage off your unit's nameplate and multiply by its voltage (usually 240 V).

A 5-ton central AC (60,000 BTU/hr) — one of the largest common residential sizes — typically draws about 4,700–5,800 watts while running. That follows the same rule of thumb used across this page: roughly 1,000–1,200 watts per ton of cooling capacity at full load, so 5 tons works out to roughly 5,000–6,000 W. A high-SEER2 system sits toward the lower end; an older or less efficient unit toward the higher end. Five-ton systems are usually reserved for larger homes and carry a correspondingly larger electrical load, so they need a properly sized dedicated 240-volt circuit. Starting (surge) wattage can briefly reach 2–3× the running figure. Always confirm the exact draw from your unit's nameplate amperage rather than relying on estimates.

Running watts are what the AC draws once it is in steady operation. Starting watts — sometimes called locked-rotor amperage (LRA) — are the surge of power the compressor and fan motors draw in the first few seconds of startup. For central AC, starting watts can be roughly 2–3 times the running watts. This surge is important when sizing a portable generator: a generator that can handle running wattage may not handle the startup surge, so always size a generator for the starting wattage of your AC.

A rough estimate: a 3-ton central AC drawing about 3,500 watts running at around $0.15 per kWh (around recent Tampa Bay area rates — confirm yours with your utility) costs roughly $0.53 per hour of runtime. If the system runs an average of 10–12 hours per day during Florida's long cooling season, that works out to approximately $5–$6 per day, or $150–$185 per month, for that one system. Actual costs vary significantly based on your system's efficiency, home insulation, thermostat settings, and current utility rates.

Generator sizing for AC is more complex than just matching running watts. You need to account for the much higher starting (LRA) surge the compressor draws at startup — which can be 2–3 times the running wattage. A 3-ton AC with ~3,500 running watts may require a generator rated for 7,000–10,000+ watts to handle startup. Soft starters can reduce the surge. Generator sizing also depends on what else runs simultaneously. Hales AC recommends consulting a licensed electrician or HVAC professional for proper generator sizing rather than estimating from wattage tables alone.

The most reliable steps are: schedule annual maintenance so the system runs at its designed efficiency (a dirty coil, low refrigerant, or restricted airflow all force the system to work harder and draw more power); upgrade to a higher-SEER2 system when replacement is due; use a programmable or smart thermostat to avoid cooling an empty home; keep the thermostat set as high as comfort allows; seal duct leaks; and ensure attic insulation is adequate. Comfort Club maintenance members get professional tune-ups that help the system perform closer to its rated efficiency.

Mini-splits can be highly efficient, and many single-zone units are rated at very high SEER2 values. However, total electricity use depends on the number of zones, the size of the space being cooled, and whether the home also has a central system for other areas. A properly sized and installed ductless mini-split in a single zone can use significantly less electricity than running a central system to condition the same zone.

Look for the nameplate or data label on the outdoor condenser unit or indoor air handler. It will list rated voltage, amperage (amps), and sometimes watts or kilowatts. You can estimate watts by multiplying amps by volts (for a 240-volt system: amps × 240 = approximate watts). The nameplate amperage is usually the running amperage at rated conditions; locked-rotor amperage (LRA) for startup surge may be listed separately.