AC Unit Buying Guide: What Homeowners Need to Know

Buying an AC unit often starts after a long inland heat wave, leaving you with a replacement quote that’s difficult to understand: two model numbers, a SEER2 figure, a refrigerant called R-454B, and a price you’re not sure is fair. The most important decisions go beyond the equipment itself, and several rules changed in 2025 and 2026, making some older advice outdated.

This guide takes each decision in order, so you can replace your air conditioner knowing what you’re paying for. It’s the same conversation Service Champions has had with homeowners across Los Angeles, Orange, Riverside, and San Bernardino counties since 2000. We walk through what’s happening, what it costs, and what we’d do if it were our own home.

How do you know it’s time to buy a new AC unit?

The clearest signals are repairs that keep coming back, rooms that never cool evenly, energy bills that climb without a change in how you use the system, and parts that are getting harder to find. One of these is worth a conversation with a technician; two or three together usually mean it’s time to price a replacement.

These six signs suggest your current system is nearing the point where replacement makes more sense than another repair:

• The same problem has needed a service call more than once.
• Some rooms stay warm no matter where the thermostat is set.
• Summer bills keep rising while your habits stay the same.
• The system runs almost nonstop on hot afternoons and still falls behind.
• Your technician mentions that parts are discontinued or on back order.
• The house feels clammy even when the air coming out of the vents is cool.

Should you repair or replace a 10-year-old AC unit in Orange County?

Age alone doesn’t determine whether replacement is necessary. A well-maintained 10-year-old system in a coastal Orange County home that rarely runs may have years left, while the same system in a hotter inland neighborhood may be nearing the end of its lifespan. The decision should depend on repair costs, repair frequency, refrigerant type, efficiency, and comfort.

The table below shows how each of these factors points toward repairing or replacing a 10-year-old system:

A system installed around 2016 almost certainly runs on R-410A. That refrigerant can still be used to service existing systems, and the section on what changed in 2025 and 2026 explains what it means when you replace it.

When a Service Champions technician from our Brea office, which serves Orange County, looks at your system, you’ll see the repair cost and the replacement cost side by side, along with what we’d do if it were our own home. For more scenarios, read our guide on whether to repair or replace an AC unit in a Southern California home.

What type of AC system is right for a Southern California home?

Most homes with existing ductwork replace a central split system, which pairs an outdoor condenser with an indoor coil on a furnace or air handler. Homes without ducts, as well as room additions and garage conversions, are often better served by ductless mini-splits.

The table below compares the four main system types by how they work, where they fit best in Southern California, and what to watch for:

How do you choose the right size AC unit for your home?

The right size comes from a room-by-room load calculation, such as ACCA Manual J, not from square footage or the size of the unit you’re replacing. A load calculation estimates how much heat your home gains on a design-temperature day, based on its insulation, windows, orientation, air leakage and occupancy. AC size is measured in tons, and one ton of cooling equals 12,000 BTU per hour.

Choosing the wrong AC size can lead to higher costs and reduced comfort. An oversized unit cools the air quickly and shuts off before it removes enough moisture, so it short-cycles, wears faster and leaves the house feeling clammy. An undersized unit runs nonstop and still falls behind on the hottest afternoons.

These five details, common in Southern California homes, often change the size a load calculation recommends:

• Ductwork in the attic of a tract home, where summer attic heat adds to the load.
• Stucco walls and roof color, which affect how much heat the house absorbs.
• Large west-facing windows or sliding doors that take the full afternoon sun.
• Room additions, converted garages or enclosed patios added since the old unit went in.
• New windows, added insulation or air sealing that can shrink the load.

Size is one decision of several. Our checklist of factors to consider before purchasing an air conditioner covers the rest.

What SEER2 and EER2 ratings should a new AC unit have in California?

California is in the federal Southwest region, so a new split-system central AC under 45,000 BTU/h must reach at least 14.3 SEER2 and 11.7 EER2, or 9.8 EER2 when its SEER2 is 15.2 or higher. Larger split systems must reach 13.8 SEER2 and 11.2 EER2 under the same rule, 10 CFR 430.32.

SEER2 measures how efficiently a system cools across a typical season. EER2 measures how efficiently it cools at full load on a hot day. In inland heat, EER2 tells you more about how the system will perform on the afternoons that matter most.

The table below lists the minimum ratings the U.S. Department of Energy sets for each system type installed in California:

These are minimums. A system can meet them and still be a poor fit if it’s the wrong size or installed with leaky ducts.

Single-stage, two-stage or variable-speed: Which is worth it?

For homes that run the AC through long, hot inland afternoons, a two-stage or variable-speed system is usually worth the extra cost, while a single-stage system often makes sense in milder coastal homes that run the AC less. Here’s how the three work.

A single-stage system runs at full capacity until the house reaches the set temperature, then shuts off. A two-stage system has a high and a low setting, so it spends most mild days on the quieter low stage. A variable-speed system adjusts its output continuously to match the load.

The trade-off involves balancing comfort, humidity control, and noise levels against upfront costs. More stages usually mean steadier temperatures, better moisture removal and quieter operation.

Which high-efficiency AC systems and brands make sense for Riverside County heat?

No single brand wins in the Riverside County heat. What matters most is a properly matched outdoor and indoor combination with a strong EER2 rating, installed and charged correctly.

The rating on a brochure usually describes the outdoor unit with a specific indoor coil. The certified rating of your exact matched combination, listed under its AHRI reference number, is what describes the system you’re buying, so ask for that number on the quote.

Local conditions shape the choice. The Temecula and Murrieta corridor sees extreme summer heat with wide day-night swings, and the county mixes newer master-planned communities with older homes in the city of Riverside. In areas with sustained heat, a higher EER2 rating and variable-speed operation may help offset their higher upfront costs through energy savings. Homeowners in milder coastal areas of Southern California may take longer to recover the additional investment.

Service Champions’ Murrieta office serves southern Riverside County and our Colton office serves northern Riverside County. We service equipment from 18 HVAC and plumbing brands, including Carrier, Daikin, Lennox, Mitsubishi, Rheem, and Trane, so our recommendations are based on your home’s needs rather than a single product line.

Two of Service Champions’ written guarantees protect a high-efficiency upgrade if the system doesn’t perform as promised:

• Comfort Guarantee: if the installed system doesn’t heat or cool to the promised range, Service Champions replaces it at no charge.
• No Lemon Guarantee: if the compressor fails twice within five years, you get a new outdoor AC unit.

If you’re planning to upgrade before summer, spring is the time to start. It leaves room for the load calculation, the permit and the field verification before the first heat wave arrives.

What changed for new AC units in 2025 and 2026?

Three major changes affect Southern California buyers: new refrigerants, the end of the federal tax credit, and updated California Energy Code requirements for permits filed on or after January 1, 2026.

The table below summarizes each change and what it means for your purchase, with more detail after it:

Refrigerant. Since January 1, 2025, new residential AC and heat pump systems must use a refrigerant with a global warming potential under 700, so new equipment ships with R-454B or R-32. Under the EPA Technology Transitions rules, systems whose components were all made before 2025 have no installation deadline, and the restrictions apply to new systems rather than to servicing existing R-410A units. If a quote lists R-410A for a new system, ask when the equipment was manufactured.

Federal tax credit. The 25C Energy Efficient Home Improvement Credit can’t be claimed for property placed in service after December 31, 2025, according to the IRS Instructions for Form 5695. Any article or sales pitch that promises a federal AC tax credit in 2026 is out of date.

California 2025 Energy Code. Permit applications filed on or after January 1, 2026 follow the 2025 standards. Replacing an AC system counts as an alteration and requires registered compliance documents. Required field verification may include checks of duct leakage, airflow, and refrigerant charge. This verification is now handled through the state’s Energy Code Compliance program, which replaced the HERS program for this purpose.

How much does a new AC unit cost in Southern California?

The cost of a new central AC system installed by Service Champions in Southern California depends on system size, energy efficiency, equipment selection, and installation requirements. Service Champions offers free in-home estimates to help you understand your options and costs. You’ll receive upfront pricing before any work begins.

These ten factors have the biggest effect on what a new AC unit costs:

• Tonnage, set by the load calculation.
• Efficiency tier, measured by SEER2 and EER2.
• Single-stage, two-stage or variable-speed operation.
• AC-only or a heat pump that also heats the home.
• Replacing the furnace or air handler at the same time.
• Ductwork sealing, repair or replacement.
• A new refrigerant line set, which current refrigerants often call for.
• Electrical upgrades, such as a new disconnect or panel capacity.
• Where the equipment sits and how easy it is to reach.
• The permit and required field verification.

Service Champions offers financing options on approved credit to help homeowners manage the cost of a new heating or cooling system. Financing is subject to credit approval, and terms and conditions apply.

Every quote is backed by the No Change Order Guarantee: the price we quote is the price you pay, with no add-ons unless they’re noted in writing on the agreement.

How do you compare AC replacement quotes in San Bernardino County?

Put the quotes side by side, compare the same line items, and favor the contractor who gives a written, upfront price with model numbers before any work begins. If two quotes don’t list the same things, they aren’t really comparable yet.

Frequent triple-digit summer temperatures in the Inland Empire can pressure homeowners into accepting the first quote they receive. Unless your home has no cooling during extreme heat, a day or two spent comparing is usually time well spent, and a good contractor will expect you to ask questions.

The checklist below shows what every AC replacement quote should include, why each item matters, and the red flag to watch for:

Service Champions’ Colton office serves San Bernardino County. Our Highest Value Guarantee means that if you find a lower published, apples-to-apples price for a comparable installation, Service Champions pays you the price difference plus an additional $50. It’s one of nine written guarantees that come with the work. You can verify our California contractor license, CSLB #799170, with the Contractors State License Board before you sign.

What happens on AC installation day?

Most AC replacements are completed in a single day. The crew removes the old equipment, installs and starts up the new system, and schedules the permit inspection for a later visit. With Service Champions, you know who’s coming and what to expect at each step.

Here’s how a Service Champions installation day runs, from start to finish:

• Before we arrive, you get an email with your technician’s photo ID, so you know who’s coming to your door.
• The crew lays floor protectors and drop cloths along the path to the equipment.
• The old equipment is disconnected, removed and hauled away.
• The new system is installed, charged with refrigerant and started up.
• Your technician walks you through the thermostat and shows you where the filter goes and how often to change it.
• The city inspection and third-party field verification for your permit are scheduled for a later visit.

The Installation Workmanship Guarantee covers how the crew works in your home: floor savers, no smoking or swearing, and same-visit fixes if anything falls short of our standards. The Better Than We Found It Guarantee means your home is left cleaner than we found it, or Service Champions pays for a cleaning service. For a deeper walkthrough, read everything you need to know about a new ac installation.

How do you keep a new AC unit running well for years?

Change filters on schedule, keep the outdoor unit clear of plants and debris, and book a professional tune-up every year. Regular air conditioner maintenance catches small problems, like a weak capacitor or a clogged condensate drain, before they turn into a breakdown on the hottest day of the year.

CHAMP-Rewards, our maintenance membership, makes that schedule easy to keep. It includes seasonal A/C and furnace tune-ups, member-only discounts on repairs and upgrades, and an extended warranty for as long as your membership stays uninterrupted.

Your installation is also covered by the Lifetime Installation Guarantee, which provides free return service for issues caused by the original installation for as long as you own the system.

Frequently asked questions about buying an AC unit

Can you buy an AC unit online and have a contractor install it?

Sometimes, but many contractors won’t install equipment they didn’t supply, and some manufacturers limit warranty coverage on units not bought and installed through an authorized dealer. You’d still need a matched indoor coil, a permit and field verification.

Can a new AC unit improve indoor air quality?

Yes, to a degree. A properly sized new system can help by controlling humidity better and running with a cleaner filter. Air quality depends more on filtration, duct sealing and ventilation, which is why Service Champions offers a separate indoor air quality assessment.

Do you need a new thermostat with a new AC unit?

Not always. A single-stage system often works with your existing thermostat, but two-stage and variable-speed systems usually need a compatible thermostat to use their lower settings. Your technician will confirm before installation.

What paperwork should you keep after a new AC is installed?

Keep the signed agreement with model numbers, the AHRI certificate for your matched system, warranty registration, the finaled permit with its compliance documents, and every maintenance record. These documents can help with warranty claims and provide useful records when you sell your home.

Are there rules about where the outdoor AC unit can go?

Yes. Manufacturer clearance requirements, local setback and noise regulations, and HOA guidelines can all affect where the outdoor unit can be installed. Your installer should check them before the permit is filed, especially if the new unit moves from the old spot.