Should You Replace Your Furnace and AC at the Same Time? A SoCal Guide
Replacing the furnace and air conditioner together usually makes sense when one system has failed and the other has reached the second half of its service life, because the two share a blower, a coil connection, and ductwork that decide how well new equipment performs. Replacing only one works when the other is newer, uses a current refrigerant, and matches the new equipment’s airflow and controls. This guide shows you how to decide, what Southern California code adds to the project, and what to gather before you request an in-home estimate.
Liberty Plumbing Heating Air Conditioning designs and completes heating system installations throughout Murrieta, Winchester, and the surrounding Southern California communities. We hold California Contractor License #761640, which you can verify at cslb.ca.gov, and we carry full general liability and workers’ compensation insurance. Our company maintains a BBB A+ Rating and 4.9 stars across more than 496 verified Google reviews, our NATE Certified technicians hold an industry-recognized HVAC credential, customers confirm our work independently on Yelp, and we hold Angi Approved Pro status. Call (951) 760-4215 to schedule an in-home estimate with a load calculation.
Why Your Furnace and Air Conditioner Work as One System
Most Southern California homes use a split system: an outdoor condensing unit, an indoor evaporator coil, and a furnace whose blower moves air through both the coil and your ducts. In cooling season, the furnace never lights, yet its blower and cabinet still carry the entire air conditioner load. In heating season, the same blower, filter, and ducts deliver the warm air. The two systems are separate machines that share one air path.
That shared air path explains why replacement decisions interlock. The blower sets the airflow your new air conditioner receives, and the U.S. Department of Energy puts the target near 400 to 500 cubic feet per minute for each ton of air-conditioning capacity. The coil must fit the furnace cabinet and match the outdoor unit. The ducts must carry that airflow without leaking it into the attic. Each of those pieces either helps new equipment reach its rated performance or holds it back.
The same agency notes that split-system heat pumps with the correct refrigerant charge and airflow usually perform very close to their listed ratings. The principle applies equally to a furnace-and-air-conditioner pairing, and it is the reason installers match the outdoor unit, coil, and blower instead of treating each one as a standalone purchase.
When Replacing Both Together Makes Sense
A combined project usually fits when one or more of these situations apply:
- One system has failed and the other has passed the middle of its service life. Furnaces often serve 15 to 20 years, while air conditioners that run most of the year often wear out sooner, so a failed air conditioner next to a 15-year-old furnace points toward replacing both.
- The air conditioner still uses R-22 refrigerant. The EPA’s HCFC phaseout schedule limited R-22 production and import to use in equipment manufactured before January 1, 2010, and ended both in 2020. Repairs on these systems now depend on recovered and reclaimed supply.
- The existing blower or coil limits the new system. An older single-speed blower, or a coil that does not match the new outdoor unit, can keep a new air conditioner from reaching its rated performance.
- The ducts need work. Sealing or correcting ducts fits naturally into a full replacement, and the Title 24 tests then cover the finished system in one visit.
- Comfort problems have lingered. Uneven rooms, short cycling, and humidity complaints often trace back to sizing, and a fresh load calculation corrects both systems at once. Our article on how oversized heating systems create comfort problems explains the pattern.
- You want one project, one schedule, and one inspection round. A combined installation typically means one coordinated permit and inspection process and one financing arrangement instead of two separate projects. Our financing options cover the full scope.
When Replacing Just One System Can Work
Replacing one system is a reasonable choice when the other is newer and healthy. We check these points before we recommend it:
- Age and history. The remaining system is roughly under eight to ten years old, has no major repair history, and uses a current refrigerant if it is the air conditioner.
- Blower match. The blower motor type and capacity deliver the airflow the new equipment needs.
- Coil and cabinet fit. The coil and furnace cabinet physically match the new equipment, or we replace the coil along with the outdoor unit.
- Controls. The thermostat wiring supports the new equipment’s features.
- Ducts. The ductwork passes inspection and the Title 24 testing that applies to the project.
If those checks come back clean, replacing one system keeps the project smaller without hurting performance. If they do not, replacing both lets you solve the limitation once instead of revisiting it later.
Warning Signs Your System Is Nearing the End of Its Service Life
The signs below suggest it is time to compare repair and replacement. Our guide to the key indicators that it is time to replace your old furnace lists more furnace-specific clues.
- Repeat repairs. Two or more repair visits in a single season often signal that major parts are wearing out together.
- Age. A furnace past about 15 years and an air conditioner past about 10 to 12 years deserve a closer look.
- Uneven comfort. Hot and cold rooms point to sizing or duct problems that new equipment alone will not fix.
- Short cycling or constant running. A system that starts and stops every few minutes, or never stops, is not matching your home’s load.
- Rising energy use. Bills that climb while your habits stay the same often reflect declining efficiency.
- An R-22 label. The data plate on the outdoor unit shows the refrigerant type, and R-22 changes the repair-versus-replace math.
- Visible wear. Rust, water stains, or soot near the furnace and coil call for a professional inspection.
Quick Decision Guide: Your Situation and the Usual Answer
| Your Situation | What We Usually Recommend | Why |
|---|---|---|
| Air conditioner failed, furnace is 15 or more years old | Replace both | The old blower and cabinet would have to serve the new coil, and the furnace is nearing the end of its range. |
| Furnace failed, air conditioner is 5 to 8 years old and healthy | Replace the furnace, then verify the match | A newer air conditioner can stay if the new blower delivers the airflow it needs. |
| Both systems are 12 or more years old and still running | Plan a combined replacement | Planning ahead avoids a breakdown and gives you time to compare options. |
| Air conditioner uses R-22 refrigerant | Replace the air conditioner and evaluate the furnace | Repairs depend on limited recovered supply, and the coil usually changes with the outdoor unit. |
| Rooms run unevenly and the ducts leak | Replace both and correct the ducts together | One load calculation and one duct test cover the whole system. |
| An addition or garage has no ductwork | Consider a ductless system for that space | A mini-split heats and cools the space without extending ducts. |
Your Replacement Options
A combined replacement gives you room to choose the system type, not just a like-for-like swap. Liberty installs each option, and our pages on air conditioner replacement and furnace installation explain the equipment in more detail.
| Option | How It Works | Fits Best When |
|---|---|---|
| Gas furnace and air conditioner | A gas furnace heats, a matched outdoor unit and coil cool, and one blower serves both seasons. | Your home already has gas service and ducts, and you want strong heat on the coldest nights. |
| Heat pump with an air handler | One outdoor unit heats and cools, and an indoor air handler moves the air. | You want a single system for both seasons, since winters here stay mild. |
| Ductless mini-split | Wall-mounted indoor heads connect to an outdoor heat pump, with no ducts. | You are conditioning an addition, a garage, an ADU, or a home with failing ducts. |
For a heat pump, the Department of Energy explains that an air-source heat pump can provide efficient heating and cooling for your home, and that SEER matters more than HSPF in warmer climates. Our technicians compare each option against your home’s layout, your gas and electric service, and the equipment you own today.
What a Combined Replacement Looks Like
- In-home evaluation and load calculation. We inspect both systems, record model and age data, and calculate your home’s heating and cooling load instead of sizing by square footage.
- Duct and airflow inspection. We check the ducts for leaks, damage, and undersized returns, because they decide how well new equipment performs.
- Options and a written quote. You compare matched system options and see the full scope in writing before any work starts. Financing is available.
- Permits. We pull the required mechanical permit under our license.
- Installation. Our crew installs the furnace or air handler, coil, outdoor unit, and controls as one matched system. Our article on key safety checks during professional furnace installation lists what a careful installer verifies.
- Testing and inspection. We test combustion, gas connections, airflow, refrigerant charge, and every safety control, then schedule the inspection and any Title 24 verification.
- Walkthrough. We show you the thermostat, the filter, and the shutoffs, and we explain how to keep the new system in good shape.
What You Can Gather Yourself Before the Estimate
A little preparation makes the in-home estimate faster and more accurate. The table separates what you can handle from what needs a licensed contractor with the right instruments.
| What Needs Doing | Who Handles It | Why |
|---|---|---|
| Photograph the data plates on the furnace, indoor coil, and outdoor unit | You | Model numbers and dates reveal age, size, and refrigerant type. |
| Note comfort problems room by room | You | Patterns point to duct or sizing issues. |
| List repairs from the past few years | You | Repair history shapes the replacement decision. |
| Load calculation for heating and cooling | Professional | Sizing depends on insulation, windows, orientation, and ducts, not square footage. |
| Duct leakage and airflow testing | Professional | Both need instruments, and Title 24 requires testing on many replacements. |
| Gas piping, venting, and electrical review | Professional | These items carry safety and code requirements. |
| Permits and inspections | Professional | A licensed contractor pulls permits and coordinates inspections. |
Why This Matters Right Now in Murrieta and Winchester
Local housing shapes the age of the equipment in your attic. The Southern California Association of Governments publishes housing profiles built from U.S. Census Bureau American Community Survey data for 2014 to 2018, and its Murrieta housing profile shows how recently the area’s homes went up. This table shows the share of homes by build period for four nearby cities.
| City | Built 2010 or Later | Built 1990 to 2009 | Built 1980 to 1989 | Built Before 1980 |
|---|---|---|---|---|
| Murrieta | 3.1% | 70.0% | 21.7% | 5.4% |
| Temecula | 5.5% | 66.4% | 21.0% | 7.1% |
| Menifee | 8.3% | 52.8% | 17.1% | 21.8% |
| Wildomar | 5.9% | 45.5% | 27.6% | 21.1% |
A home built in 2000 that still has its original equipment now runs a 26-year-old furnace and air conditioner. Air conditioners made before 2010 may use R-22, and homes from the 1980s have usually seen at least one replacement already. Winchester is unincorporated, so the city profiles do not cover it, but its neighbors show how quickly the region grew in a single generation.
Replacing a furnace in western Riverside County also brings air-quality rules into play. South Coast AQMD Rule 1111 limits NOx from residential natural gas furnaces to 14 nanograms per joule, so replacement furnaces there must carry an ultra-low NOx certification. Our page on California’s new furnace emissions standards explains what that means for equipment choice. Rules can change, and San Diego County falls under a different air district, so we confirm the requirement for your address before we order equipment.
A furnace or air conditioner replacement typically needs a mechanical permit. Murrieta homeowners work with Murrieta Building & Safety, and unincorporated Winchester falls under the County of Riverside Building and Safety Department. California’s Energy Code, Title 24, Part 6, covers alterations and additions to existing buildings, and the 2025 standards took effect on January 1, 2026. For replacement systems, the code adds testing such as duct leakage, airflow, and refrigerant charge verification, and a HERS rater verifies the results where required. A combined project runs those tests once.
Fall also gives you time to plan. The peak cooling season has passed, so you can compare options, schedule the work, and finish before the next heat wave without making a rushed decision during a breakdown. Incentive programs for efficient equipment change often, so ask which ones apply when you request your written quote.
Why Murrieta and Winchester Homeowners Choose Liberty Plumbing Heating Air Conditioning
We earn trust the way an installation should earn it, with credentials you can verify before we ever arrive.
| What We Offer | What It Means for Your Replacement Project |
|---|---|
| NATE Certified Technicians | Industry-recognized HVAC competency certification that supports accurate sizing, installation, and diagnosis. |
| Master Licensed Contractor, CA License #761640 | Verifiable at cslb.ca.gov any time. California requires a licensed contractor for permitted work, and every permit we pull carries this license number. |
| Fully Insured (General Liability and Workers Compensation) | Zero financial exposure for your property or your household during every visit. |
| BBB A+ Accredited Business | Third-party verified track record at bbb.org. No unresolved complaints across 25-plus years of service. |
| 4.9 Stars Across 496 Verified Google Reviews | Hundreds of Murrieta, Winchester, and Southern California homeowners confirm our service quality. |
| Yelp Guaranteed and Highly Rated | Independently verified service quality with additional customer protection. |
| Angi Approved Pro | Background-checked and independently verified contractor status on Angi. |
| 3-Year Exclusive Performance Guarantee on HVAC Repairs | If the specific issue we diagnosed and repaired returns within three years because of our repair, we address it. |
| In-Home Estimate With a Load Calculation | We size your system to your home, not to a guess based on square footage. |
| Written Quote Before Work Begins | You see the equipment, the scope, and the plan before any work starts. |
| Permits Handled Under Our License | We pull the required permits and coordinate the inspections. |
| American Standard HVAC Products | Dependable equipment with strong parts and warranty support. |
| Financing Available | Spread out the project instead of delaying a replacement you need. |
| 25-Plus Years Serving Southern California | Deep familiarity with local housing, water, climate, and permit conditions. |
| Veteran-Owned and Operated | A company built on precision, accountability, and getting the job done correctly the first time. |
Frequently Asked Questions: Replacing a Furnace and AC at the Same Time
Should I replace my furnace and air conditioner at the same time?
It often makes sense when one system has failed and the other has reached the second half of its service life. The two share a blower, a coil connection, and ductwork, so new equipment performs best when everything matches. If the other system is newer, healthy, and compatible, replacing only one can work. A technician checks age, blower match, refrigerant type, and ducts before recommending either path.
Can I replace just my air conditioner and keep my old furnace?
Yes, when the furnace is in good condition and its blower delivers the airflow the new air conditioner needs. The new coil must also fit the furnace cabinet, and the thermostat wiring must support the new equipment. We verify those points in the in-home estimate. An aging furnace, or a blower that limits airflow, usually tips the decision toward replacing both.
Can I replace just my furnace and keep my old air conditioner?
Yes, if the air conditioner is healthy, uses a current refrigerant, and works well with the new furnace blower. A new blower can change the airflow across the existing coil, so we check that match first. An air conditioner that uses R-22 or has a repair history often makes a combined replacement the better choice.
How old is too old for a furnace or air conditioner?
Furnaces often serve 15 to 20 years, and air conditioners that run most of the year often wear out sooner. Age alone does not decide the question. Repair history, refrigerant type, comfort, and efficiency all matter, so we weigh them together and explain your options honestly.
What is a matched system, and why does it matter?
A matched system pairs an outdoor unit, an indoor coil, and a blower or air handler that manufacturers rate to work together. Correct pairing, refrigerant charge, and airflow help the equipment reach its rated performance. A mismatched pairing can fall short of those ratings and strain the equipment.
Does replacing both at once save money?
It can reduce duplicated work, because one project means one evaluation, one permit process, one round of Title 24 testing, and one installation schedule. Total cost depends on the equipment, your ducts, and your home, so we give you a written quote before any work starts. Financing is available for the full project.
Should I replace a furnace and AC with a heat pump instead?
A heat pump can heat and cool your home with one system, and the Department of Energy notes that SEER matters more than HSPF in warmer climates. Mild Southern California winters suit heat pumps well. The right choice depends on your ducts, your electrical service, and your preferences, so we compare gas and heat pump options for your home.
How do you size a new furnace and air conditioner for my home?
We perform a load calculation that accounts for your home’s insulation, windows, orientation, duct system, and local climate. Square footage alone leads to oversizing, and oversized equipment short cycles, wears faster, and leaves rooms uneven. A correct calculation protects comfort and efficiency for both systems.
Do I need new ductwork when I replace both systems?
Not always. We inspect your ducts for leaks, damage, and undersized returns. We seal and reconnect sound ducts, while damaged or undersized sections need repair or replacement. California’s Title 24 also requires duct testing on many replacements, so a combined project handles the testing once.
Do I need a permit to replace a furnace and AC in California?
Replacing a furnace, coil, air handler, or outdoor unit typically needs a mechanical permit from your local building department. Title 24 adds testing such as duct leakage, airflow, and refrigerant charge verification, and a HERS rater verifies the results where required. We pull the permits under our license and coordinate the inspections.
What are California’s low-NOx rules for a new gas furnace?
South Coast AQMD Rule 1111 limits NOx from residential natural gas furnaces to 14 nanograms per joule in western Riverside County, so replacement furnaces there must carry an ultra-low NOx certification. San Diego County falls under a different air district. Rules can change, so we confirm the requirement for your address before we order equipment.
What if my air conditioner still uses R-22 refrigerant?
The EPA ended R-22 production and import in 2020, so technicians service existing R-22 systems with recovered and reclaimed supply. Repairs can become harder to complete as that supply tightens. If your outdoor unit shows an R-22 label, we walk through repair and replacement options so you can plan ahead.
How long does it take to replace a furnace and air conditioner together?
Most residential installations take one to two days, depending on the system type, the condition of your ducts, and your home’s layout. We confirm the schedule in your written quote, including any permit and inspection steps.
When is the best time of year to replace both systems?
The best time is before a breakdown. Fall gives you time to compare options and finish before the next cooling season, and winter and spring work for the same reason. A planned replacement lets you choose equipment calmly instead of reacting to a failure on the hottest or coldest day.
How can Liberty Plumbing Heating Air Conditioning help me decide?
Liberty Plumbing Heating Air Conditioning holds California Contractor License #761640, employs NATE Certified technicians, carries full insurance, and maintains a BBB A+ Rating with 4.9 stars from more than 496 verified Google reviews. We inspect both systems, run a load calculation, and give you an honest recommendation and a written quote, whether the answer is one system or both. Call (951) 760-4215 to schedule an in-home estimate.
When to Call Liberty Plumbing Heating Air Conditioning
Call us when your furnace or air conditioner fails, when either system has reached the second half of its service life, or when you want to plan a replacement before a breakdown forces the decision. Our NATE Certified technicians inspect both systems, run a load calculation, explain your options in plain language, and give you a written quote before any work begins. Financing is available, and we handle the permits and inspections under our license.
Liberty Plumbing Heating Air Conditioning holds California Contractor License #761640, carries full general liability and workers’ compensation insurance, and serves Murrieta, Winchester, Temecula, Menifee, Wildomar, and the surrounding communities. These items help the estimate go smoothly:
- Photos of the data plates on the furnace, indoor coil, and outdoor unit
- A short list of comfort problems by room
- Repair visits you remember from the past few years
- Any refrigerant label you see on the outdoor unit
| Call Liberty Plumbing Heating Air Conditioning at (951) 760-4215 to schedule your in-home replacement estimate NATE Certified | BBB A+ Rated | CA License #761640 | Fully Insured | Financing Available | 24/7 Emergency | Veteran-Owned |
