What Size Window Air Conditioner Unit Can I Run on Regular House Wiring

Window AC Units

• Window air conditioner units cool incoming air using a refrigerant material that absorbs existing heat and transfers it to a condenser unit. The condenser unit expels the heat to the outdoors and cools the refrigerant. A blower device then blows air across the cooling coil to produce cool air. Air conditioner sizes differ in terms of their cooling capacities, so a unit with a 5,000 BTU (or British Thermal Unit) capacity has less cooling power than one with a 15,000 BTU capacity. BTU capacity has to do with how much heat a unit can remove from the air per hour in a specific amount of space.

Regular House Wiring

• A home’s electrical wiring operates off of alternating current, meaning electrical currents alternate between certain ranges or voltages. Regular house wiring operates on a 220-volt circuit board made up of two separate 110-volt circuits. Most electrical devices in a home only require one 110-volt breaker. This means electrical currents alternate between 0 and 110, though most circuits allow for ranges up to 125 volts. As circuit boards normally include two 110-volt circuits, most homes can accommodate any size window air-conditioning unit.

110-Volt Circuits

• Air conditioners also carry different voltage requirements in addition to BTU capacities. An air conditioner’s voltage requirement usually calls for either a 115-, 125- or 220 volt circuit. Air-conditioning units with less than 9,000 BTU capacities can also operate off of a 110-volt circuit, which means the air conditioner will use a standard three-pronged outlet.

220-Volt Circuits

• Air conditioner units with BTU capacities of 15,000 or more have a 220-volt requirement. For older model homes, most wall outlets only provide 110-volts, so an outlet may require rewiring before you plug in one of these large units. In effect, rewiring involves drawing electrical current from both sides of the circuit board, since each side houses 110-volt circuits. A 220-volt plug outlet may also have different hole configurations compared to the standard three-pronged outlet. A wall outlet for a 220-volt air conditioner will normally appear as three rectangular holes that form a triangle, though some air-conditioners may require a four-pronged outlet.