High Electric Bill in Summer? Why Your AC Runs Too Much

Most common causes

1. Dirty filter or coils. Dirt on the filter, indoor coil, or outdoor coil cuts efficiency, so the system runs longer to remove the same heat.
2. Leaky ductwork. Ducts in a hot attic that leak or are poorly insulated lose cold air before it reaches the rooms, so the system runs more.
3. Thermostat settings. A very low setpoint, no schedule, or a fan set to On instead of Auto all add run time and energy use.
4. Refrigerant leak. A low charge lowers cooling capacity, so the AC runs longer. The leak must be found and repaired.
5. Aging system. Older systems lose efficiency over time, and older equipment was built to lower efficiency standards than new systems.
6. Heat gain in the house. Poor attic insulation, unshaded west facing windows, and air leaks let heat in faster, especially in Santa Clarita summers.
7. Something else using power. Pool pumps, extra refrigerators, and electric vehicle charging also add up in summer, so the AC is not always the only cause.

What you can safely check

• Replace the air filter.
• Set the thermostat fan to Auto, not On.
• Raise the setpoint a few degrees when you are away and use a schedule or a smart thermostat.
• Clear debris around the outdoor unit and rinse the fins gently with a hose from the outside in, with the power off at the disconnect.
• Close blinds on sunny windows in the afternoon.
• Make sure supply vents are open and return grilles are not blocked.
• Compare this bill to the same month last year to see if usage really jumped.

What affects the repair cost

A filter and thermostat changes cost very little. A maintenance visit with coil cleaning can restore lost efficiency. Duct sealing depends on how much duct is damaged. A refrigerant leak repair depends on location and refrigerant type. If the system is old, a technician can help compare the cost of repairs against a more efficient replacement.

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