Home Cooling & AC Efficiency
Home cooling and AC efficiency: how to stay cool for less
Cooling is the single largest driver of a summer electricity bill. If your house is like most in the US, air conditioning runs hardest during the same months electricity gets more expensive, which is why a July bill can land far above an April bill even when nothing else in the home changes. Air conditioning accounted for about 19% of all electricity used in US homes in 2020, and close to 90% of households now run some form of it, according to U.S. Energy Information Administration data.
Summer 2026 raises the stakes. EIA's 2026 Short-Term Energy Outlook projects residential electricity prices rising about 5% this year, to an average near 18.2 cents per kWh, alongside a hotter cooling season with roughly 4% more cooling degree days than 2025. Two levers control what cooling costs: how efficiently you cool your home, and the supply rate you pay for each kWh. Arbor, an automated energy service, helps households in deregulated states with the rate lever, and the equipment and habit decisions here address the efficiency lever.
Key takeaways
- Cooling is the biggest summer load. Air conditioning drove about 19% of US home electricity use in 2020, and its share of the bill climbs sharply in July and August.
- Two levers control the cost. How efficiently you cool, through equipment and settings, and the supply rate you pay per kWh, all move the bill. Most households work on neither.
- Prices and heat are both up in 2026. EIA projections show residential rates rising about 5% while the country sees roughly 4% more cooling degree days than last year.
- Equipment sets your ceiling. A right-sized, efficient air conditioner or heat pump can use a fraction of the power an old or oversized unit draws for the same comfort.
- Settings and habits do the rest. Thermostat temperature, fan use, and basic maintenance routinely shift a cooling bill by 10% or more.
Why your summer electric bill climbs
A summer bill rises for two reasons at once, and they compound. Hot weather pushes air conditioners to run longer, so the home uses more kWh. At the same time, wholesale electricity prices climb with regional demand, which lifts variable rates and utility default rates. A household whose usage rises and whose rate also rises sees a bill increase larger than either change alone.
Usage gets the blame, but the rate often does as much damage. Customers on a utility default rate or an expired fixed-rate contract pay more for every kWh, and a hot month multiplies that gap. Grab two summer bills and compare both the kWh used and the per-kWh supply rate. If usage explains the jump, focus on efficient cooling. If the rate climbed, moving to a competitive fixed rate addresses it directly.
How much does it cost to run an air conditioner?
Cost depends on the unit's power draw, how many hours it runs, and the rate per kWh. Central air conditioning in an average-sized home can consume more than 2,000 kWh per year, according to the Department of Energy. At the 2026 average residential rate of 18 cents per kWh, that is roughly $360 a year, concentrated into a handful of peak months.
Smaller units are easier to estimate. A mid-size window air conditioner drawing about 1,000 watts uses 1 kWh per hour, so running it eight hours a day costs close to $1.50 per day at current rates, or about $45 over a month. To estimate the cost for any unit:
- Multiply the unit's wattage by the number of hours it runs each day.
- Divide that figure by 1,000 to convert it to daily kWh.
- Multiply the daily kWh by your per-kWh supply rate, then by 30 for a monthly estimate.
Your latest bill and the understanding your electric bill guide show where to find that rate.
Choosing an air conditioner: portable, window, mini-split, and central
Households cool their homes with four main types of air conditioners, and they differ in upfront cost, how much space they cover, and how much power they use.
| AC type | What it cools | Upfront cost | Best suited to |
| Window unit | One room | Low | Renters, single rooms, supplementing central air |
| Portable unit | One room, less efficiently | Low to moderate | Rooms where a window unit cannot be mounted |
| Ductless mini-split | One to several rooms | High (installed) | Homes without ducts, additions, room-by-room control |
| Central air | Whole home | Highest (installed) | Homes with existing ductwork that want uniform cooling |
Portable and window air conditioners
Window units and portable units both cool a single room, and both make sense for renters, bedrooms, and homes without central air. A window unit mounts in the window frame and vents heat directly outside. A portable unit sits on the floor and vents through a hose run to a window.
Do portable air conditioners actually work, and are they worth it? They do cool a room, but most single-hose models are less efficient than a comparable window unit, because they exhaust conditioned indoor air and pull warm replacement air in through gaps in the home. A window unit usually cools the same room for less money. A portable unit earns its place when a window unit cannot be installed safely, for example with casement or high windows, or building rules that prohibit window units.
For a bedroom, or any room, size the unit to the space rather than buying the largest one available. A common Department of Energy benchmark is 20 BTU per square foot of living space, with room air conditioners generally ranging from 5,500 to 14,000 BTU per hour. Add about 600 BTU for each regular occupant beyond two, and about 4,000 BTU if the unit cools a kitchen. An oversized unit cools the air quickly but shuts off before it removes enough humidity, leaving the room cold and clammy, so a correctly sized unit that runs longer is both more comfortable and more efficient. For bedroom use, look for the ENERGY STAR label and a quiet decibel rating.
Ductless mini-splits
A ductless mini-split pairs an outdoor compressor with one or more indoor air handlers, linked by a conduit that needs only a small hole through an exterior wall. Without ducts, a mini-split avoids the energy losses of central forced-air systems, which the Department of Energy notes can exceed 30% of cooling energy. One outdoor unit can feed up to four indoor heads, so different rooms can be set to different temperatures.
Is a mini-split worth the cost? It costs more upfront than a window unit, sometimes about twice as much for similar capacity, and more than a central system once ductwork is excluded. Its value shows up in homes without ductwork. For a room addition, a converted attic, or an older home with radiators or baseboard heat, a mini-split avoids the expense and disruption of adding ducts. Where a home already has sound ductwork, and the goal is uniform whole-home cooling with concealed equipment, central air is often the better match.
Can you install a mini-split yourself? Installation is simpler than a whole-house system, but the Department of Energy still recommends a professional, because correct sizing and placement of each indoor head prevent short cycling and humidity problems. Refrigerant handling is federally regulated, and an improper installation commonly voids the manufacturer's warranty. Pre-charged do-it-yourself kits exist, yet most households get better long-term efficiency from a professional install.
Central air conditioners and high-efficiency upgrades
Central air conditioners circulate cooled air through ducts and come in two forms: split systems, with an outdoor and an indoor component, and packaged units, which house everything in one cabinet. Their efficiency is measured by SEER, the seasonal energy efficiency ratio, where a higher number means less electricity for the same cooling. That test standard was updated to SEER2 in 2023, and current Department of Energy minimums sit near 13.4 SEER2 in northern states and 14.3 SEER2 in southern states.
What SEER rating should you look for? Meet your region's minimum at a baseline, then weigh how hard the system will work. A mid-range efficiency unit suits moderate climates and light use, while a higher rating, with newer systems reaching the mid-20s, pays back faster in hot climates with long cooling seasons. Premium efficiency costs more upfront, so the heaviest users gain the most.
Are inverter air conditioners worth the extra cost? An inverter, or variable-capacity, system runs its compressor at low speed most of the time instead of cycling fully on and off. It holds temperature more steadily, removes humidity better, runs quieter, and uses less energy than a comparable single-speed unit. That premium is easiest to justify in hot climates and in homes where even cooling and low noise matter.
How to cool your home without air conditioning
Air conditioning is not the only way to stay comfortable, and the alternatives use far less electricity when the climate suits them. Most work best alongside steps that keep heat out of your home.
- Ceiling and portable fans. Fans do not lower the air temperature, but moving air across the skin makes a room feel cooler. A ceiling fan lets you raise the thermostat about 4°F with no loss of comfort, and on mild days it can replace the air conditioner entirely. Fans cool people rather than rooms, so turn them off when you leave.
- Whole-house fans. A whole-house fan pulls cool outdoor air in through open windows and exhausts warm air through the attic and roof. It works when outdoor air is cooler than indoor air, which usually means evenings, nights, and early mornings, and it uses a small fraction of the energy an air conditioner does. It does not dehumidify or filter the air, needs adequate attic venting, and requires open windows to prevent dangerous backdrafting from gas appliances.
- Evaporative (swamp) coolers. An evaporative cooler passes outdoor air over water-soaked pads, which cools the air 15°F to 40°F before it enters the home. Department of Energy figures show these units cost about half as much to install as central air and use about a quarter of the energy. Do they actually work? Yes, but only in dry climates. They add moisture to the air, so they are ineffective and even counterproductive in humid regions, and they need a water supply and monthly maintenance.
- Keep heat out. Close blinds and curtains on sun-facing windows, add exterior shade where possible, seal air leaks, and run heat-generating appliances like ovens and dryers in the cooler parts of the day.
A whole-house fan and an air conditioner work best as a pair rather than as rivals. Dry or mild climates let a whole-house fan handle most cooling for far less money, while hot, humid conditions leave an air conditioner as the only option that controls both temperature and humidity. Many households run the fan overnight and in shoulder weather and save the air conditioner for peak heat.
Cooling an apartment cheaply combines these tools. Use fans and shading, ventilate at night, cool only the room you occupy with a right-sized window or portable unit, and set that unit as high as is comfortable. Renters in deregulated states have one more option: lowering the electricity supply rate reduces the cost of every cooling kWh, with no landlord approval required.
AC settings and habits that lower cooling costs
Small changes to how an air conditioner is run add up across a long summer, and none of them require new equipment.
What temperature should you set your AC to? Department of Energy guidance recommends 78°F when you are home in summer, and setting it as high as is comfortable from there. Every degree lower increases cooling energy use, so the gap between 72°F and 78°F is significant over a season.
Is it cheaper to leave the AC on all day or turn it off? For most homes, letting the temperature rise while you are out saves energy, because the unit runs less overall even though it works harder on your return. Department of Energy figures put the savings at as much as 10% a year from setting the thermostat back 7°F to 10°F for eight hours a day. Turning the system fully off during extreme heat can let humidity build up and leave the home slow to recover, so a setback, ideally automated with a programmable or smart thermostat, is the practical middle ground.
Will running a ceiling fan let you set the AC higher? Yes. A ceiling fan creates enough air movement to let you raise the thermostat about 4°F with no loss of comfort, which trims cooling costs directly. Run fans only in rooms that are occupied.
How cold should you set the AC at night? From a cost standpoint, letting the temperature drift up overnight saves money, and lower outdoor temperatures help the home hold a higher setting. Many people sleep better cooler, so a ceiling fan or bedroom fan is an efficient compromise: it lets you keep the air conditioner a few degrees higher while still feeling cool. Avoid chilling the whole house to cool one bedroom, and cool that room with a fan or a small unit instead.
How do you prepare an AC for summer? A short pre-season checklist keeps the system running efficiently through peak heat:
- Clean or replace the air filter before the season, then monthly during heavy use.
- Clear leaves and vegetation away from the outdoor condenser so airflow is not blocked.
- Confirm that supply and return registers are open and unobstructed.
- Schedule a professional tune-up before peak heat.
- Seal duct leaks, since central duct losses can exceed 30% of cooling energy.
Repair or replace? When to upgrade your cooling system
A failing air conditioner forces a choice between another repair and a new system, and a few signals point clearly toward replacement. ENERGY STAR advises that if an air conditioner or heat pump is more than 10 years old, it is worth considering a replacement, and a correctly installed high-efficiency unit can cut cooling and heating costs by up to 20%. Frequent repairs, rising bills despite steady usage, uneven cooling between rooms, and an older system that still uses R-22 refrigerant all strengthen the case.
Should you repair or replace your AC? One common industry guideline multiplies the repair estimate by the unit's age in years, and many contractors treat a result above roughly $5,000 as a signal to replace. A 12-year-old unit facing a $500 repair clears that line, while a 5-year-old unit with the same repair does not. Efficiency gains shorten the math further, because a new system can use noticeably less power for the same comfort.
Is a heat pump better than central AC? In cooling mode, a heat pump operates exactly like an air conditioner, using the same refrigeration cycle and the same SEER2 efficiency scale. What differs is that a heat pump also reverses to heat the home in winter. For a household already replacing an air conditioner, a heat pump delivers the same cooling while replacing or supplementing the heating system, which is why the Department of Energy suggests considering one in place of a split-system AC.
Will a heat pump cool a home effectively? Yes. A properly sized, ENERGY STAR-certified heat pump cools just as well as a comparable central air conditioner, because the cooling hardware is essentially the same. Federal 25C tax credit support for efficient equipment ended after 2025, but many states and utilities still offer rebates on high-efficiency cooling systems, so check local programs before buying.
The fastest way to lower your summer electric bill
Efficient equipment, thermostat settings, fans, and maintenance all work on one lever, using fewer kWh to cool the home. None of them changes the price of the kWh you still use, including baseline cooling, refrigeration, and other loads that run no matter how careful you are.
A second lever is the supply rate. Deregulated states make the supply portion of an electricity bill competitive, and you can choose your supplier. Moving from a utility default rate or an expired fixed-rate contract to a competitive fixed rate lowers the cost of every kWh the home uses, including summer cooling, without any change to the thermostat. A self-audit using the understanding your electric bill and compare electricity rates guides shows whether the current rate is competitive.
Arbor functions here as a year-round home energy advisor rather than a summer-only fix. It checks your supply rate, compares competitive fixed-rate plans in your utility territory, secures a better rate when one exists, and monitors the contract so you do not roll onto a higher variable rate before the next cooling season. Arbor's service is no cost to you and works for both renters and homeowners in deregulated markets.
The cheapest summer is the one where both levers are handled. Cool the home efficiently with the right equipment and settings, and pay a competitive rate for the power that cooling still requires. Your next step: pull your latest bill, find the per-kWh supply rate, and see if it is competitive. If you would rather not do that math yourself, Arbor checks it for you.
Home cooling FAQs
What temperature should I set my AC to, including at night? Department of Energy guidance recommends 78°F while you are home in summer, set as high as is comfortable from there, since every degree lower raises cooling energy use. At night, letting the temperature drift up saves money, and cooler outdoor air helps the home hold the higher setting. If you sleep better cool, a ceiling or bedroom fan lets you stay comfortable a few degrees warmer.
Is it cheaper to leave the AC on all day or turn it off? Letting the temperature rise while you are out is cheaper for most homes because the system runs less overall. A setback of 7°F to 10°F for eight hours can save as much as 10% a year. Turning the system fully off in extreme heat can let humidity build, so a programmable or smart thermostat that eases the temperature up and back down is the better approach.
Are portable air conditioners worth it? A portable unit cools a single room but is usually less efficient than a window unit of the same capacity, so it costs more to run. It is worth buying when you cannot install a window unit because of casement windows or building rules that prohibit them.
Is a mini-split worth the cost, and can I install one myself? A mini-split costs more upfront than a window unit, and more than central air once ductwork is set aside, but it pays off in homes without ducts, in additions, and where room-by-room control is wanted. Older homes that lack ductwork are a strong fit, because a mini-split needs only a small hole through an exterior wall. Installation is simpler than a whole-house system, but the Department of Energy recommends a professional: correct sizing prevents short cycling, refrigerant handling is federally regulated, and a do-it-yourself install often voids the warranty.
What SEER rating should I look for, and are inverter ACs worth it? Meet your region's minimum first, near 13.4 SEER2 in northern states and 14.3 SEER2 in southern states. A higher rating costs more upfront and pays back faster in hot climates with long cooling seasons. An inverter system, which runs its compressor at variable speed instead of cycling on and off, improves humidity control, lowers noise, and reduces energy use, and that premium is easiest to justify for heavy users.
Should I repair or replace my AC, and is a heat pump worth considering? Replacement is usually the better choice for a unit more than 10 to 15 years old, one needing frequent repairs, or one with rising running costs, and a common guideline multiplies the repair cost by the unit's age, with a high result favoring replacement. When replacing, consider a heat pump: in cooling mode, it works exactly like an air conditioner and cools just as effectively, while also heating the home in winter.
Does a swamp cooler actually work? An evaporative cooler works well in dry climates, where it can lower incoming air temperature by 15°F to 40°F using about a quarter of the energy of central air. It adds humidity to the home, so it is not effective in humid regions.
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