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Common problems
High summer electric bills
Your electric bill jumps every summer, or it’s higher than neighbors with similar homes. Before replacing the air conditioner, find out where the cooling goes: much of it can be lost in the attic before it reaches a room.
What it usually means
- Cooling is usually the biggest summer load, so a high bill means the AC is working hard, working inefficiently, or both. Compare a summer bill with a spring or fall bill, when you used little heat or AC: the difference is roughly what cooling costs you.
- The usual culprits are heat getting in (through the attic, unshaded west and south windows and air leaks) and cooling getting lost (leaky or uninsulated ducts in a hot attic, garage or crawlspace).
- ENERGY STAR estimates that in a typical house, 20 to 30 percent of the air moving through the duct system is lost to leaks, holes and poorly connected ducts.
Where it’s most common
Our climate research lists this as a common problem in these metro areas. Each guide covers what homes there need, local audit programs and rebates.
- Hot and humid Dallas–Fort Worth · Greater Houston · Miami · Tampa · Orlando · San Antonio · Austin
- Hot and dry Phoenix · Riverside
- Mixed New York City · Atlanta · Washington, DC · Philadelphia · Charlotte · Baltimore · St. Louis
Somewhere else? Find your metro guide.
Likely causes, by climate
The same symptom has different causes in Miami, Phoenix and Minneapolis. Find your climate below; the tag marks the climates where this problem is most common.
Hot and humid Florida, Texas and the Gulf Coast Common here
Cooling runs most of the year, and the AC also has to pull moisture out of the air. Ducts and the air handler often sit in a vented attic that gets far hotter than the outdoor air, so every leak loses cooled, dried air and pulls in hot, humid air. Oversized and older single-speed systems waste energy on short runs.
Hot and dry the desert Southwest and inland Southern California Common here
Months of extreme heat make the AC the biggest bill. The attic climbs well above the outdoor temperature, so attic ducts, thin attic insulation and west-facing windows add the most load. On the hottest afternoons, the rating that matters most is EER2, the efficiency at 95°F outdoors, not just SEER2.
Mixed the Mid-Atlantic, St. Louis and the Southeast Piedmont Common here
Summers are hot and muggy, so the same attic, duct and window problems apply, plus damp basements and crawlspaces that add moisture the AC has to remove. If you have both a gas and an electric bill, the electric bill’s summer peak is the one to study.
Cold the Northeast, Great Lakes, Upper Midwest and Colorado Front Range
Summers are shorter, so a high summer bill often points to something besides central AC: window units cooling hot upstairs rooms, a basement dehumidifier running nonstop, an old second refrigerator or freezer, or a pool pump. A bill analysis separates these from cooling.
Marine and mild coastal the Pacific Northwest and coastal California
Most homes need little cooling, so a summer spike usually comes from heat waves in homes built without AC, portable or window units running in upstairs rooms, or high electricity prices, especially in coastal California. Shading and a well-sealed, insulated attic keep upstairs rooms cooler for less.
Not sure which climate you’re in? Your metro guide says, and the climate zone entry explains the map builders use.
How an audit confirms it
Guessing is how people end up with new equipment that doesn’t fix the problem. These tests measure the cause. Ask for them by name when you book; each guide explains what the results mean and what to do next.
- Energy bill analysis Separates cooling from the rest of your use by comparing summer bills with spring and fall, so you know how much is really the AC.
- Duct leakage test Measures how much cooled air the ducts lose. Ask for leakage to outside, the part that wastes energy.
- Attic inspection Checks attic insulation against ENERGY STAR’s level for your climate zone, and whether attic ducts are sealed and insulated.
- Blower door test Measures how leaky the house is, which is how hot, humid outdoor air gets in.
- Infrared (thermal) scan With the AC running on a hot afternoon, shows warm patches where insulation is missing and air leaks in.
- Manual J load calculation A Manual J load calculation works out the cooling load too, so you know the right size before you replace the AC.
Try first (cheap or free)
- Change or clean the AC filter, and keep plants and debris away from the outdoor unit.
- Close blinds or shades on sunny east, west and south windows, and add exterior shading where you can.
- Set the thermostat a few degrees higher when you’re away or asleep, and use ceiling fans in rooms you’re in. Fans cool people, not rooms, so switch them off when you leave.
- Read your bills: if summer use is far above spring and fall, it’s cooling. If every month is high, look at year-round loads like pool pumps, old refrigerators and water heating.
- If your utility has time-of-use rates, run laundry, the dishwasher and other big loads outside the peak hours.
The fix ladder
From the cheapest step to the biggest. Work up only as far as you need to, and test again after.
- Shades, a thermostat schedule and fresh filters
- Seal and insulate ducts in the attic, garage or crawlspace
- Air seal the attic floor, then add insulation; in hot climates, add a radiant barrier under the roof deck
- Solar control at the windows: exterior shade screens, awnings, or low-SHGC glass when windows are replaced
- Replace an old or oversized system with a right-sized, high-efficiency AC or heat pump, sized by Manual J
When to call a pro
- The AC runs but the air from the vents isn’t cool, or there’s ice on the refrigerant lines or indoor coil. Switch to fan only so it thaws, and call an HVAC technician.
- Bills jumped with no change in weather or habits. A refrigerant leak or a failing part can do that.
- You’re about to replace the system. Ask for a Manual J load calculation in writing, not a size based on square footage or the old unit.
Common mistakes
- Replacing the AC before checking the ducts: a new unit on leaky attic ducts still loses its cooling to the attic.
- Buying on SEER2 alone in a very hot, dry climate: compare EER2 too, because that’s the efficiency on the hottest afternoons.
Paying for the fixes
Utility programs often pay toward audits, duct sealing, insulation and heat pumps, and some require an audit first. Your metro guide lists the programs near you, and your state’s page covers state and federal rebates.
Words worth knowing
- SEER / SEER2
- An air conditioner's or heat pump's cooling efficiency averaged over a whole cooling season; higher is better.
- EER / EER2
- Cooling efficiency measured at one hot test condition rather than averaged over a season; useful for judging performance on the hottest days.
- Cooling degree days (CDD)
- A measure of how hot a place is: each day adds how far its average temperature rises above 65°F. More degree days means more air conditioning.
- Duct leakage test
- A test that pressurizes your heating and cooling ducts with a calibrated fan to measure how much air escapes through leaks.
- Duct leakage to outside
- The part of duct leakage that escapes outside the heated and cooled space, into attics, crawlspaces, garages or outdoors.
- Radiant barrier
- A shiny foil layer, usually in attics, that reflects the sun's radiant heat; it helps most in hot, sunny climates.
- Solar heat gain coefficient (SHGC)
- The share of the sun's heat a window lets into the house, from 0 to 1; lower keeps homes cooler, higher adds free winter heat.
- Baseload
- The energy a home uses no matter the season — fridge, lights, electronics, water heating and standby power — apart from heating and cooling.
- Time-of-use (TOU) pricing
- Electricity prices that change with the time of day, usually cheapest overnight and highest when demand peaks.
- Manual J (ACCA load calculation)
- The US industry standard for calculating how much heating and cooling a house needs, room by room, so equipment can be sized correctly.
The glossary explains every term on the site.
Common questions
Will a new, higher-SEER2 air conditioner fix high summer bills?
Sometimes, but check the ducts and attic first. A new unit connected to leaky ducts in a hot attic still loses cooled air, and a unit bigger than the house needs runs short cycles that waste energy and remove less humidity. Seal and insulate the ducts, improve the attic, then size any replacement with a Manual J load calculation.
What’s the difference between SEER2 and EER2?
SEER2 rates cooling efficiency across a typical season. EER2 rates it at one hot condition, 95°F outdoors. In very hot climates, where the AC spends long hours at or above that temperature, a higher EER2 matters as much as a higher SEER2.
How do I know how much of my bill is air conditioning?
Compare a summer bill with a spring or fall bill from a month when you used little heat or AC. The difference is roughly your cooling cost. An energy bill analysis does this properly, adjusting each month for the weather.
Related problems
Sources
Where each problem is common comes from our regional climate research (NOAA climate normals, EPA, PNNL, FEMA and others), cited on each metro guide. The guidance on this page follows these sources, checked October 26, 2026:
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