Furnace and AC Replacement in Modesto
Replacing a furnace or an air conditioner in Modesto is a permitted job with California energy code checks attached, and done properly it can come with an MID rebate. Done without a permit, it usually forfeits that rebate.
When replacement makes sense
The equipment age is only part of it. A furnace past about 15 years that needs a major part, an air conditioner on R-22 with a leak, or a system that has needed something every season for three years are the usual triggers. So is a cracked heat exchanger, which ends a furnace regardless of age.
Modesto's housing makes this a common conversation. Most of the city was built in the 1970s and 1980s, and the tracts in Village One, Sylvan and Salida that followed are now 20 to 30 years old. Many of those houses are on original or first-replacement equipment.
The permit and what the energy code adds
California treats replacing a furnace, air conditioner, heat pump or coil as an alteration under the Title 24 energy code, and it needs a permit from the City of Modesto (or Stanislaus County for unincorporated addresses such as Salida). The installer normally pulls it.
Duct testing
When the equipment is replaced and the existing ducts stay, the code generally requires the ducts to be tested for leakage and sealed if they leak beyond the allowed limit, unless an exception applies (for example, a short run of duct outside the conditioned space). In a 1980s Modesto attic, ducts often fail the first test, and sealing them is some of the most useful money in the whole job.
Third-party verification
Some of these checks have to be confirmed by an independent HERS rater, not just the installer, before the city signs off. That is a separate small cost, and a quote should say whether it is included.
Why it is worth doing
The permit and tests are what make a new system perform as rated. They are also what MID asks to see before paying a rebate. Ask anyone quoting you whether the price includes the permit, and if it does not, ask why.
MID rebates
If MID supplies your electricity, its 2026 Home Rebate Catalog lists rebates on central air conditioners and heat pumps that meet Consortium for Energy Efficiency tiers: roughly $350 to $600 for an air conditioner and $450 to $700 for a heat pump, depending on tier, plus $350 per indoor head on qualifying ductless mini-splits. The catalog requires installation by a CSLB contractor in good standing with a C-20 licence, a matching indoor coil on split systems, an AHRI certificate, a copy of the permit, the paid invoice, and an application within 90 days of purchase. Amounts depend on funding when the application arrives, so check mid.org before you sign. Turlock and parts of Ceres are on TID, which runs its own program.
Furnace and AC, or a heat pump
A heat pump replaces both the air conditioner and, in most Modesto homes, the furnace's job too. It makes most sense where electricity is cheap relative to gas, so ask the company quoting to run the numbers on your actual MID or TID rate and your PG&E gas bill, and where the ducts are in decent shape. A gas furnace paired with a new AC still makes sense in plenty of houses, especially if the furnace is young and only the AC has failed.
A dual-fuel setup (heat pump plus gas furnace as backup) splits the difference and is worth asking about if you are replacing both at once.
Refrigerant has changed
Since 2025, most new residential air conditioners and heat pumps sold in California use lower-impact refrigerants such as R-454B or R-32 instead of R-410A. They need matching indoor coils and line sets checked for compatibility. That is one reason a new outdoor unit on an old indoor coil is generally not an option any more, and why a quote that replaces only the condenser deserves a question.
Sizing
Bigger is not better. An oversized air conditioner cools the house quickly, shuts off before it dehumidifies or reaches the far rooms, and cycles hard. A proper quote is based on a load calculation for your house (insulation, windows, orientation, duct condition), not on the tonnage of the old unit. Ask how they sized it.
What it costs
Local companies generally quote somewhere around $4,000 to $8,000 for a gas furnace replacement, $7,000 to $14,000 for a central air conditioner with its coil, and $12,000 to $22,000 or more for a full system or a ducted heat pump. Attic installs, duct replacement, electrical upgrades and two-storey homes push toward the top. Permit, duct sealing and HERS verification should be line items.
Pricing a replacement? Call and describe the house and the system. A local heating and air company will come out and quote it.
Common questions
Do I need a permit to replace my furnace in Modesto?
Yes. Replacing a furnace, air conditioner, heat pump or coil is a permitted alteration in California. The installer normally pulls it from the City of Modesto or, outside city limits, Stanislaus County.
Does MID give a rebate on a new air conditioner?
MID's 2026 catalog lists rebates for qualifying central air conditioners and heat pumps, installed by a C-20 contractor, with a permit copy, within 90 days of purchase. Check current amounts at mid.org.
How long does a replacement take?
A straightforward like-for-like swap is often a day. Adding duct work, an attic install, or switching to a heat pump can take two or three, plus the inspection.
Should I replace the furnace and AC together?
If both are old, usually yes: they share the blower and coil, and doing both once is cheaper than twice. If the furnace is young, replacing only the AC and coil is reasonable.
Do you install systems?
No. We are an advertising and referral service. An independent licensed heating and air company quotes and installs.
Other heating and cooling work in Modesto
- Furnace Repair in Modesto, CA
- AC Repair in Modesto, CA
- Heat Pump and HVAC Repair in Modesto
- Furnace and AC Tune-Ups in Modesto
- Air Filtration for Modesto Homes
Also serving
Furnace & AC Replacement is available beyond Modesto, across Salida , Riverbank , Ceres and Turlock .
Get help with furnace & ac replacement
Say what the system is doing and a local heating and air company will get back to you about a visit. Answered Mon–Sat, 8am–6pm · after hours we call back the same day Or call (209) 842-0950. If you have no heat or no cooling right now, calling is faster.