How Much Does It Cost to Run a Central Air Conditioner (3 Ton)?

Roughly 3,000 to 4,500 W while running, depending on efficiency. A quick estimate is the BTU rating divided by the SEER: 36,000 divided by 14 gives about 2,600 W for the compressor, plus 400 to 800 W for the indoor blower and outdoor fan.

At 3,500 W, 8 hours a day and a 50 percent duty cycle, about 420 kWh a month. That is around $73 at the national average rate, $55 in a 13 cent state and over $135 in California. Hot climates with longer run times can double those figures.

Usually not without a soft starter. The compressor's locked-rotor start can exceed 10,000 W, which trips the overload on most generators under 10 kW. With a soft starter installed, a 7,500 to 9,000 W generator can often handle it. See the generator sizer.

Yes. A standard blower uses 400 to 600 W, so running it continuously adds 10 to 14 kWh a day, more than a third of the compressor's own energy in the default example. Use 'auto' unless you need the circulation for filtration or comfort.

About 61 cents for each hour the compressor runs, since a 3 ton system at 3,500 W uses 3.5 kWh and 3.5 x $0.173 = $0.61. Averaged over an hour at a 50 percent duty cycle, it is about 30 cents an hour.

About $2.42 a day on the default of 8 hours at a 50 percent duty cycle: 3.5 kW x 8 x 0.5 = 14 kWh, and 14 x $0.173 = $2.42. Running all 24 hours at the same duty cycle uses 42 kWh, about $7.27 a day.

Yes, it is usually the largest electrical load in a home during summer. A 3 ton system draws about 3,500 W while running on a 240 V circuit, and the EIA estimates that space cooling accounts for roughly 19 percent of annual electricity use in US homes.

It depends on how many rooms you cool. On this site's defaults, one 8,000 BTU window unit uses about 3.6 kWh a day and a 3 ton central system about 14 kWh, so cooling one or two rooms with window units costs less. Cooling the whole house with four or more window units uses about as much as the central system, and an efficient central system will usually win.

Only with enough capacity and a soft starter. At 3,500 W, a 13.5 kWh battery carries about 3.9 hours of compressor run time (13.5 divided by 3.5), and the default 14 kWh a day would empty it in about a day. The battery's inverter also has to handle a start-up surge that can reach 10,000 W, which is why most installers add a soft starter.

Raise the thermostat while you are away or asleep and keep the system clean. The DOE estimates you can save up to 10 percent a year on heating and cooling by setting the thermostat back 7 to 10 degrees for 8 hours a day. Changing the filter on schedule, keeping the outdoor coil clear and sealing leaky attic ducts all reduce run time too.