HVAC accounts for about half your electric bill
The U.S. Department of Energy puts it at 43–47% of the average household’s energy consumption. In South Carolina, where summers are long and hot, that number often trends higher — particularly in July and August when the system runs nearly continuously on 95°F days.
The challenge is that your power bill doesn’t break down costs by appliance. You get a total kWh figure and a dollar amount. To understand where HVAC sits in that number, you need to do a bit of math.
How to estimate your HVAC cost
Find your system’s rated wattage. For a central air conditioner, it’s usually on the data label on the outdoor unit (compressor amps × voltage = watts). A typical 3-ton central AC draws about 3,500 watts. At South Carolina’s average retail rate (~$0.12–$0.14/kWh), that’s roughly $0.49–$0.56 per hour of operation.
If your system runs 8 hours a day in July (a reasonable average for a well-sized, well-maintained system), that’s about $4/day or $120/month just for cooling. If your bill is $280 and HVAC is $120, the remaining $160 covers everything else.
Signs your HVAC cost is higher than it should be
- Bill spikes year-over-year without obvious cause (weather was similar)
- System runs longer to reach setpoint than it used to
- Recent spike after a service call or refrigerant recharge that didn’t fully fix the problem
- Dirty coils (reduces efficiency 15–40% when significantly fouled)
- Duct leaks (10–30% of conditioned air lost in unconditioned attics is common in older homes)
The fastest ways to lower the number
- Clean or replace the air filter — a clogged filter makes the system work harder
- Have the coils cleaned — outdoor condenser coils clogged with debris drop efficiency significantly
- Program the thermostat — 1°F increase in cooling setpoint ≈ 3% reduction in cooling energy
- Shade the outdoor unit — a unit in direct afternoon sun works harder; shade trees or a pergola can help
- Seal duct leaks — in homes with accessible ductwork, mastic or foil tape on leaky joints is a one-time fix with lasting savings
If your bills have trended up over several years on a system that’s seen regular maintenance, it may be efficiency degradation in aging equipment. A system’s rated SEER is its efficiency when new; after 10–15 years, real-world efficiency can drop 10–25%. At some point the energy savings from a new high-efficiency system start offsetting the capital cost.
