Why did my electric bill suddenly go up?

The most common HVAC causes: a clogged air filter forcing longer run-times, a refrigerant leak causing constant operation, dirty condenser coils reducing efficiency, or an aging system losing efficiency. Also check for rate increases or new high-draw appliances before attributing it to HVAC.

How much does a dirty air filter affect energy bills?

A severely clogged filter can increase HVAC energy use by 5-15% by forcing the system to work harder to move air. This is the easiest fix -- filter replacement typically costs $10-$30 and takes five minutes.

Can an old AC unit cause high electric bills?

Yes. A 15-year-old 8-9 SEER system can cost 40-60% more per season than a modern 16-18 SEER2 replacement. If your bills have been rising gradually over several years and the system is aging, efficiency degradation is a likely cause.

HVAC Guide

Why Is My Energy Bill So High?

Heating and cooling accounts for 40-50% of home energy use in most climates. When energy bills spike unexpectedly, HVAC is usually the place to start. Here are the most common causes and what each fix costs.

HVAC Causes of High Energy Bills

Dirty air filter: A clogged filter makes the system work harder to move air, increasing run-time and energy use. Check and replace your filter -- this is the most common and easiest fix.
Low refrigerant (leak): A system running low on refrigerant must run longer to achieve the same cooling, driving up electricity use. Signs: bills rising steadily over 2-3 seasons, system runs constantly, rooms do not reach setpoint.
Dirty coils: Both the evaporator coil (inside) and condenser coil (outside) need to be clean to transfer heat efficiently. A dirty condenser coil is a common cause of high summer bills.
Aging system running inefficiently: A 15-year-old system running at 8-9 SEER vs. a modern 16 SEER2 replacement can cost 40-60% more per cooling season. If bills have been creeping up for years with no obvious cause, system age is a likely factor.
Duct leaks: Leaky ductwork can waste 20-30% of conditioned air. Ducts in unconditioned spaces (attic, crawlspace) are the most common leak points.
Thermostat and controls: A malfunctioning thermostat that reads temperature incorrectly can cause the system to run far more than needed. A simple replacement ($100-$300) can resolve the issue.

Non-HVAC Causes to Rule Out

Before assuming HVAC is the culprit, check: new electric vehicles or EV chargers added to the home, new appliances with high energy draw, changes in occupancy or usage patterns, utility rate increases, and billing period changes. Compare bills month-over-month to the same month last year.

Frequently Asked Questions

Why did my electric bill suddenly go up?: The most common HVAC causes: a clogged air filter forcing longer run-times, a refrigerant leak causing constant operation, dirty condenser coils reducing efficiency, or an aging system losing efficiency. Also check for rate increases or new high-draw appliances before attributing it to HVAC.
How much does a dirty air filter affect energy bills?: A severely clogged filter can increase HVAC energy use by 5-15% by forcing the system to work harder to move air. This is the easiest fix -- filter replacement typically costs $10-$30 and takes five minutes.
Can an old AC unit cause high electric bills?: Yes. A 15-year-old 8-9 SEER system can cost 40-60% more per season than a modern 16-18 SEER2 replacement. If your bills have been rising gradually over several years and the system is aging, efficiency degradation is a likely cause.

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