Air Conditioner Questions, Answered

Most central AC filters are disposable, so you replace them instead of cleaning them. Turn the system off, remove the old filter, and slide in a new one of the same size with the arrow facing the unit. ENERGY STAR says to check it monthly; Trane says change it every 1 to 3 months. Mini split heads usually have washable screens, so follow the manual.

Check the simple things first: thermostat on Cool and below room temperature, a clean filter, open vents, an untripped breaker, and a clear outdoor unit. If you see ice, turn the system off. Problems past that point, like a failed capacitor or a refrigerant leak, involve electrical parts or refrigerant and need a professional.

This Old House puts an installed central AC at $6,345 to $10,575 in 2026, averaging $8,460, and Fixr's range is $5,800 to $14,400. Those are national numbers. In Sacramento, the price should also cover the permit, the third-party duct and refrigerant tests the 2025 Energy Code requires, and any duct sealing.

A mini split, or ductless mini split, has an outdoor unit connected by refrigerant lines to one or more indoor heads on a wall or ceiling, so no ductwork is needed. ENERGY STAR says they fit homes without ducts, additions, and rooms with hot or cold spots. ENERGY STAR describes them as heat pumps, so they heat in winter as well as cool in summer.

An air conditioner moves heat from inside your house to the outdoors. Refrigerant absorbs heat at the indoor evaporator coil, a compressor in the outdoor unit pressurizes it, and the outdoor condenser coil and fan release that heat outside. The indoor blower pushes the cooled air through your ducts, and the coil pulls moisture out of the air, which drains away.

The right size comes from a Manual J load calculation, which accounts for insulation, windows, sun exposure, and ducts. The Department of Energy says the old one-ton-per-400-to-500-square-feet rule ignores those factors. As a rough reference, This Old House says most 1,500-square-foot homes need about 2.5 tons.

Switch the thermostat from Cool to Off and let the ice melt. Don't chip at it; Trane warns that can damage the coil. Then check for a dirty filter or blocked return vents, the most common causes. If the filter is fine, or the coil freezes again, low refrigerant from a leak is likely, and that needs a technician.

Trane lists a clogged condensate drain line, a cracked or rusted drain pan, a frozen coil that drips as it thaws, a dirty filter, and improper installation as the usual causes. Turn the system off, mop up the water, and call for service. Ask about an overflow safety switch, which shuts the system down before the pan spills.

Set it a few degrees warmer than your daytime setting. ENERGY STAR's programmable thermostat guidelines used 78°F mornings and evenings and 82°F overnight, and the Department of Energy suggests raising the temperature while you sleep. A ceiling fan can make a setting about 4°F warmer feel just as comfortable. Keep vulnerable family members and pets in mind.

This Old House says the best home cooling systems usually last 12 to 15 years, depending on use. ENERGY STAR suggests having a system evaluated once it passes 10 years, and the Department of Energy lists that age, frequent repairs, and uncomfortable rooms as reasons to consider replacing. Regular maintenance helps equipment last longer.

Turn the thermostat to Off, switch off the AC breaker, wait a few minutes, then turn the breaker back on and set the thermostat to Cool. Some units have a reset button or a drain safety switch that needs attention first; check your manual. If the breaker trips again, leave it off and call for service.

An inverter AC uses a variable-speed compressor that slows down and speeds up to match the cooling the house needs, instead of cycling between full power and off. That typically means steadier temperatures. SMUD calls these variable-stage systems and pays its top heat pump rebate, $3,000, for one that replaces gas heat.

For the outdoor coil, turn the power off at the thermostat and disconnect, clear away debris, and rinse gently with a garden hose, as Roseville Electric suggests. Skip the pressure washer. The indoor evaporator coil is harder to reach and sits near wiring, so ENERGY STAR lists its cleaning as part of a contractor's maintenance visit.

A musty smell can point to standing water or debris in the drain pan or line. A burning or electrical smell can mean an overheating motor or wiring, so turn the system off at the thermostat and breaker and call for service. A rotten-egg smell near the furnace may be a gas leak: leave, then call 911 and PG&E at 1-800-743-5000.

Turn the system off at the thermostat and the outdoor disconnect. Remove leaves and debris, trim plants back about 2 feet as SMUD and Trane recommend, and rinse the coil gently from the top down with a hose. Don't open the electrical panel; capacitors store energy, and that part of the job belongs to a technician.

Generally no. Lennox says a full plastic or vinyl cover can trap moisture, cause rust, and draw rodents. A breathable top cover is the most it recommends, and heat pumps that run year-round should never be covered. In the Sacramento area, keeping leaves and debris off the unit matters more than covering it.

A split system has two main parts: an outdoor unit with the compressor and condenser coil, and an indoor unit, such as a furnace or air handler with an evaporator coil, connected by refrigerant lines. A central AC with an outdoor unit and an indoor furnace or air handler is a split system. A packaged unit puts everything in one outdoor cabinet instead.

For jobs over $1,000, or any job that needs a permit, the contractor needs a CSLB license; the HVAC class is C-20. Anyone handling refrigerant also needs EPA Section 608 certification. You can verify a license for free on the CSLB website and confirm it's active before work begins.

Yes. The EPA says homeowners can maintain and repair existing systems for their useful life, including swapping a failed condensing unit or coil for a similar R-410A part. Only complete new systems face the lower-GWP refrigerant limit, and a May 2026 EPA rule lets leftover R-410A equipment made before 2025 still be installed.

It can still be repaired, but refrigerant is costly. The EPA says U.S. production and import of R-22 ended in 2020, so only recycled, reclaimed, or previously produced R-22 can be used. Fixr reports R-22 recharges of $500 to $2,000 or more. The EPA also warns that switching to an unapproved refrigerant can create a fire hazard.

SMUD customers can get $1,000 to $3,000 for qualifying heat pumps, according to SMUD's rebate page in November 2026, plus up to $4,000 for panel and circuit upgrades when switching from gas. PG&E and Roseville Electric didn't list AC or heat pump rebates on their residential pages, and the TECH Clean California incentives were reserved.

California's habitability rules require working heating, but the Attorney General's tenant guide does not list air conditioning, and SB 655 (2025) set a state policy on safe indoor temperatures without creating a statewide AC mandate. If AC came with your unit, your lease usually decides who fixes it. Request repairs in writing and keep copies.

The EPA recommends a MERV 13 filter, or the highest rating your system can take, running the HVAC fan on On instead of Auto, and switching any outside-air intake to recirculate. Change filters more often during heavy smoke. CARB says portable air cleaners sold in California must be certified for low ozone.