A full HVAC system replacement in Southern Maryland costs $5,000 to $16,000 in 2026, with most homeowners in Calvert, St. Mary's, and Charles County paying $7,000 to $12,000 for a new furnace and air conditioner or a heat pump system with installation. A standalone central air conditioner replacement runs $3,500 to $8,000. A furnace replacement alone costs $2,500 to $7,500. A heat pump system (which handles both heating and cooling) runs $4,500 to $12,000. A ductless mini-split system costs $3,000 to $8,000 for a single-zone unit or $8,000 to $20,000 for a multi-zone whole-house system.
September is the right time to think about this. Your air conditioner just worked its hardest through a Southern Maryland summer, humidity that stays above 70 percent for weeks, temperatures in the 90s, and a system that ran 10 to 14 hours a day from June through August. If your system struggled to keep up, ran constantly without reaching the set temperature, or made sounds it did not make last year, those are signs that it is near the end of its useful life. Replacing it now, before the first cold night in November, means you choose the system on your schedule, compare quotes without pressure, and have heat ready when you need it. Replacing it in January because the furnace died at 2 AM on a 20-degree night means you pay emergency rates, take whatever system is available, and spend a cold night in a hotel.
Here is what a full HVAC replacement costs in Southern Maryland, what each component costs separately, how to choose between system types, what Maryland rebates and federal tax credits can save you, and what to watch for during the process.
HVAC Replacement Cost by System Type
| System Type | Equipment + Installation | Best For |
|---|---|---|
| Central air conditioner only | $3,500 to $8,000 | Homes with a working furnace that only need cooling replaced |
| Gas furnace only | $2,500 to $7,500 | Homes with working AC that only need the furnace replaced |
| Gas furnace + central AC (bundle) | $5,000 to $14,000 | The traditional setup, furnace heats, AC cools |
| Air-source heat pump (ducted) | $4,500 to $12,000 | All-in-one heating and cooling, the fastest-growing choice in Maryland |
| Dual fuel system (heat pump + gas furnace) | $6,000 to $16,000 | Maximum efficiency, heat pump handles mild weather, furnace handles deep cold |
| Ductless mini-split (single zone) | $3,000 to $8,000 | Additions, converted garages, rooms without ductwork |
| Ductless mini-split (multi-zone, whole house) | $8,000 to $20,000 | Homes without ductwork, or homeowners wanting zone-by-zone control |
| Geothermal heat pump | $15,000 to $35,000 | Long-term investment for maximum efficiency, highest upfront, lowest operating cost |
What Is Included in the Installation Cost
A standard HVAC replacement, removing the old system and installing a new one using the existing ductwork, includes:
- Removal and disposal of the old equipment
- The new outdoor unit (condenser for AC or heat pump)
- The new indoor unit (furnace, air handler, or fan coil)
- The evaporator coil (connects the indoor and outdoor units)
- Refrigerant line set (copper lines between indoor and outdoor units, replaced if the old set is incompatible with the new refrigerant)
- Thermostat (a basic programmable thermostat is usually included; a smart thermostat is an upgrade)
- Electrical connections and disconnect
- Condensate drain line
- New filter and startup
- Permit and inspection (required in Calvert, St. Mary's, and Charles County)
What adds to the cost:
| Add-On | Cost |
|---|---|
| Ductwork replacement (full system) | $3,000 to $8,000 |
| Ductwork modification (partial, for a different system type) | $500 to $3,000 |
| Electrical panel upgrade (100A to 200A, often needed for heat pumps) | $2,000 to $4,000 |
| New 240V circuit for outdoor unit | $200 to $600 |
| Thermostat upgrade to smart thermostat | $150 to $400 |
| Zoning system (dampers and multiple thermostats) | $2,000 to $5,000 |
| Refrigerant line set replacement | $300 to $1,500 |
| Gas line modification or extension | $300 to $1,500 |
| Concrete pad for outdoor unit | $100 to $300 |
| Permit fees | $100 to $300 |
Central Air Conditioner Replacement: $3,500 to $8,000
If your furnace is in good condition and only the air conditioner needs replacement, you can replace just the outdoor condenser and the indoor evaporator coil.
Cost by Efficiency (SEER2 Rating)
The SEER2 rating measures cooling efficiency. Higher SEER2 means lower electricity bills but higher equipment cost. As of January 2023, the minimum SEER2 for new central air conditioners is 14.3 in the northern region (which includes Maryland).
| SEER2 Rating | Equipment Cost | Installed Cost | Annual Cooling Cost (estimate) |
|---|---|---|---|
| 14.3 to 15 (minimum efficiency) | $1,500 to $3,000 | $3,500 to $5,500 | $550 to $700 |
| 16 to 17 (mid efficiency) | $2,500 to $4,000 | $5,000 to $7,000 | $450 to $550 |
| 18 to 20 (high efficiency) | $3,500 to $5,500 | $6,500 to $8,000 | $350 to $450 |
| 21+ (ultra high efficiency) | $5,000 to $7,000 | $7,500 to $10,000 | $300 to $400 |
The efficiency math for Southern Maryland. Your AC runs hard here, the cooling season runs from late May through mid-September, with the heaviest demand in July and August when humidity drives the system as much as temperature. An upgrade from SEER2 14.3 to SEER2 18 saves roughly $150 to $250 per year on cooling costs. The equipment cost difference is $2,000 to $3,000. At $200 per year in savings, the payback period is 10 to 15 years, roughly the lifespan of the unit. The savings are real but modest. Choose mid-efficiency (SEER2 16 to 17) for the best balance of upfront cost and operating cost in this climate.
Sizing
Air conditioners are sized in tons (one ton equals 12,000 BTU per hour of cooling capacity). Proper sizing is critical, an oversized unit short-cycles (turns on and off frequently, which reduces dehumidification and increases wear), and an undersized unit runs constantly without reaching the set temperature.
| Home Size | AC Size | Typical Installed Cost |
|---|---|---|
| 1,000 to 1,200 sq ft | 1.5 to 2 tons | $3,500 to $5,000 |
| 1,200 to 1,600 sq ft | 2 to 2.5 tons | $4,000 to $6,000 |
| 1,600 to 2,000 sq ft | 2.5 to 3 tons | $4,500 to $7,000 |
| 2,000 to 2,500 sq ft | 3 to 3.5 tons | $5,000 to $7,500 |
| 2,500 to 3,000 sq ft | 3.5 to 4 tons | $5,500 to $8,000 |
| 3,000+ sq ft | 4 to 5 tons | $6,500 to $10,000 |
These are rough guidelines. Proper sizing requires a Manual J load calculation, a room-by-room analysis of insulation, windows, orientation, shading, ductwork, and occupancy. A contractor who sizes your system by square footage alone (without performing a load calculation) is guessing, and guessing leads to oversizing. Oversized systems are one of the most common HVAC installation errors, and they cause chronic comfort and humidity problems that last the life of the equipment.
Furnace Replacement: $2,500 to $7,500
Cost by Fuel Type and Efficiency
| Type | AFUE | Equipment Cost | Installed Cost | Annual Heating Cost |
|---|---|---|---|---|
| Gas furnace (80% AFUE) | 80% | $1,000 to $2,500 | $2,500 to $4,500 | $800 to $1,200 |
| Gas furnace (90 to 96% AFUE) | 90 to 96% | $1,500 to $3,500 | $3,500 to $6,000 | $550 to $800 |
| Gas furnace (97 to 98% AFUE) | 97 to 98% | $2,500 to $5,000 | $5,000 to $7,500 | $450 to $650 |
| Oil furnace | 80 to 87% | $2,000 to $4,000 | $4,000 to $7,000 | $1,200 to $2,000 |
| Electric furnace | 100% (but expensive to run) | $800 to $2,000 | $2,000 to $4,000 | $1,500 to $2,500 |
| Propane furnace | 80 to 96% | $1,500 to $3,500 | $3,000 to $6,000 | $1,000 to $1,800 |
AFUE (Annual Fuel Utilization Efficiency) measures how much of the fuel becomes usable heat. An 80% AFUE furnace sends 80 cents of every fuel dollar into your home and 20 cents up the flue. A 96% AFUE furnace sends 96 cents into the home.
The fuel question in Southern Maryland. This is the same question as the water heater guide covered: most of the tri-county area does not have natural gas. Washington Gas serves parts of Waldorf, La Plata, St. Charles, White Plains, Indian Head, and some areas near Prince Frederick and Dunkirk. Outside those areas, your options are electric, propane, oil, or heat pump.
If you have natural gas: a high-efficiency gas furnace (90 to 96% AFUE) paired with a central AC is the traditional choice and still competitive on operating cost. Gas furnaces heat fast, work in any temperature, and are well-supported by the local contractor base.
If you do not have natural gas: a heat pump is almost certainly your best option. Read the heat pump section below.
Oil furnaces are still running in some older Southern Maryland homes, but oil heating is expensive (fuel oil prices are volatile and trend upward), the equipment is less efficient than gas alternatives, and oil tanks are an environmental liability (underground oil tanks, in particular, are a real estate problem). If you are replacing an oil furnace, switching to a heat pump or propane is the forward-looking choice.
The 80% vs. 90%+ Efficiency Decision
This matters because it affects the vent type, which affects installation cost.
An 80% AFUE furnace uses a conventional metal flue vented through the chimney. If your current furnace is 80% and you are replacing it with another 80%, the venting stays the same, simple, low-cost swap.
A 90%+ AFUE furnace is a condensing furnace. It extracts so much heat from the combustion gases that the exhaust is cool enough to vent through PVC pipe through a wall, no chimney needed. But if your current furnace uses the chimney, switching to a condensing furnace means installing new PVC venting (through the wall or roof), which adds $300 to $800. The chimney flue may also need to be capped or lined for the water heater if it still uses it.
The efficiency savings (roughly $200 to $400 per year on gas) pay for the venting upgrade in 1 to 3 years, making the 90%+ furnace the better value over the life of the system.
Heat Pump Systems: $4,500 to $12,000
Heat pumps are the fastest-growing HVAC choice in Maryland, and for good reason, they heat and cool with one system, they qualify for substantial rebates and tax credits, and they cost less to operate than any other heating system except geothermal.
How Heat Pumps Work
A heat pump is an air conditioner that runs in reverse. In cooling mode, it moves heat from inside the house to outside (exactly like a conventional AC). In heating mode, it moves heat from outside air into the house. It does not generate heat by burning fuel, it transfers heat, which is why it uses far less energy than a furnace or electric resistance heater.
The cold weather concern. Older heat pumps lost efficiency below 35 to 40 degrees and needed a backup heat source (usually electric resistance strips) below freezing. Modern cold-climate heat pumps (also called hyper-heat or low-ambient heat pumps) operate efficiently down to 0 to -15 degrees Fahrenheit. Southern Maryland winters are mild, average January lows are 25 to 30 degrees, with only a handful of nights below 15 degrees per year. A modern heat pump handles a Southern Maryland winter without supplemental heat for all but the coldest nights.
Heat Pump Cost by Type
| Type | Installed Cost | Heating Efficiency (HSPF2) | Cooling Efficiency (SEER2) |
|---|---|---|---|
| Standard air-source heat pump | $4,500 to $8,000 | 7.5 to 8.5 | 14.3 to 16 |
| High-efficiency air-source heat pump | $6,000 to $10,000 | 9 to 10 | 17 to 20 |
| Cold-climate (hyper-heat) heat pump | $7,000 to $12,000 | 10 to 12 | 18 to 22 |
| Ductless mini-split (single zone) | $3,000 to $8,000 | 9 to 13 | 18 to 33 |
| Ductless mini-split (multi-zone, 3 to 5 heads) | $8,000 to $20,000 | 9 to 12 | 18 to 25 |
| Geothermal heat pump | $15,000 to $35,000 | COP 3.5 to 5.0 | 25 to 35 EER |
Dual Fuel Systems: $6,000 to $16,000
A dual fuel system pairs a heat pump with a gas or propane furnace. The heat pump handles heating in mild weather (roughly above 35 degrees), where it is the most efficient option. Below the balance point, the outdoor temperature where the heat pump's efficiency drops below the furnace's, the system switches to the furnace automatically. You get the efficiency of a heat pump for most of the heating season and the reliable, fast heat of a furnace for the coldest days.
In Southern Maryland, where winter temperatures are below the balance point only 10 to 20 percent of the heating season, a dual fuel system runs on the heat pump for roughly 80 to 90 percent of the winter, which means 80 to 90 percent of your heating is at heat pump efficiency (roughly 2 to 3 times more efficient than gas, and 3 to 4 times more efficient than electric resistance).
Dual fuel makes the most sense if you already have natural gas or propane. If you are all-electric with no gas service, a cold-climate heat pump alone handles Southern Maryland winters without needing a gas backup.
Ductless Mini-Splits: $3,000 to $20,000
Mini-splits are heat pumps without ductwork. Each indoor unit (called a head) mounts on a wall or ceiling and conditions one room or zone independently. One outdoor unit can power one to eight indoor units.
Where mini-splits make sense in Southern Maryland:
- Additions and converted spaces (garage conversions, bonus rooms, sunrooms) that do not have ductwork and would be expensive to connect to the central system
- Older homes without ductwork, some older homes in Southern Maryland have radiator heat or baseboard electric and no ductwork at all. A multi-zone mini-split provides heating and cooling without the $3,000 to $8,000 cost of installing ductwork
- Hot or cold rooms that the central system cannot adequately condition, a room over a garage, a second floor that runs hot, a sunroom
- Zone control, each head has its own thermostat, so you can heat and cool occupied rooms and leave unoccupied rooms at a setback. This is inherently more efficient than a central system that conditions the entire house to one temperature
The efficiency advantage. Mini-splits are the most efficient HVAC systems short of geothermal. Top units achieve SEER2 ratings above 30 and HSPF2 above 12, dramatically higher than any ducted system. Part of the efficiency comes from eliminating duct losses, which waste 20 to 30 percent of the energy in a typical ducted system through leaks, conduction, and poor insulation.
Maryland Rebates and Federal Tax Credits
This is where HVAC replacement in Maryland gets significantly more affordable. The combination of federal tax credits and Maryland rebate programs can reduce the cost of a qualifying heat pump system by $5,000 to $15,000 or more.
Federal Tax Credits (Inflation Reduction Act)
The 25C Residential Clean Energy Tax Credit provides tax credits for qualifying high-efficiency HVAC equipment:
| Equipment | Credit | Maximum |
|---|---|---|
| Heat pump (air-source, meeting CEE highest tier) | 30% of cost | $2,000 per year |
| Central AC (meeting CEE highest tier) | 30% of cost | $600 per year |
| Gas furnace (AFUE 97%+) | 30% of cost | $600 per year |
| Electrical panel upgrade (to support heat pump) | 30% of cost | $600 per year |
The heat pump credit is the big one. A $10,000 heat pump installation qualifies for a $2,000 tax credit. An electrical panel upgrade needed for the heat pump qualifies for an additional $600. Combined, that is $2,600 back on your federal taxes. This credit resets annually, if you do the heat pump this year and an additional qualifying improvement next year, you can claim credits in both years.
Maryland Rebates (EmPOWER and IRA Programs)
Maryland's EmPOWER programs, administered through the local utilities, provide rebates for energy-efficient HVAC equipment. The specific amounts and availability depend on your utility (Pepco, BGE, SMECO) and change periodically. As of 2026:
- Heat pump rebates through EmPOWER and the IRA Home Electrification Rebate program can provide $2,000 to $8,000 or more for qualifying heat pump installations, with higher amounts for income-qualifying households
- SMECO (Southern Maryland Electric Cooperative, which serves most of Calvert and St. Mary's County) offers rebates for heat pumps, heat pump water heaters, and insulation upgrades
- Pepco (which serves Charles County) offers similar rebates through EmPOWER Maryland
Check the current programs before you buy. Rebate amounts and program availability change. The Maryland Energy Administration (energy.maryland.gov) maintains the current list of available incentive programs. Your HVAC contractor should also be able to tell you which rebates apply to the equipment they are quoting.
The Combined Savings
For a qualifying heat pump installation, the combined federal tax credit and Maryland rebates can reduce the effective cost by $5,000 to $10,000. A $10,000 heat pump system with a $2,000 federal tax credit and a $3,000 state/utility rebate has an effective cost of $5,000, less than a standard gas furnace and AC system. This is why heat pump adoption in Maryland has accelerated dramatically.
Signs Your HVAC System Needs Replacement
Age. Air conditioners and heat pumps last 12 to 20 years, with 15 being the median. Gas furnaces last 15 to 25 years, with 20 being the median. If your system is past those midpoints, replacement is on the horizon, plan for it rather than react to a failure.
Rising energy bills. If your heating and cooling costs are climbing year over year and your usage patterns have not changed, the system is losing efficiency. All HVAC equipment degrades over time, motors wear, coils corrode, refrigerant charge drifts, and the system works harder to deliver the same output. A 15-year-old system may be operating at 60 to 70 percent of its original efficiency.
Frequent repairs. The rule of thumb: if a repair costs more than half the price of a new system, or if you have spent more than $1,000 on repairs in the last two years on a system over 10 years old, replacement is the better investment. A $1,500 compressor repair on a 14-year-old AC is buying time on equipment that will need replacement within a few years anyway.
Uneven temperatures. Rooms that are consistently too hot or too cold, despite adjustments, indicate a system that is losing capacity, ductwork that has deteriorated, or a system that was never properly sized for the house. Replacement is an opportunity to correct the sizing.
Humidity problems. Your air conditioner is also your primary dehumidifier. If the house feels clammy even with the AC running, the system is not removing enough moisture, either because it is oversized (short-cycling, which reduces dehumidification) or because the coil is degraded. In Southern Maryland, where humidity is the dominant comfort variable from May through October, a system that cannot dehumidify is a system that is not doing its job.
The R-22 refrigerant issue. If your AC or heat pump uses R-22 (Freon), which was phased out of production in 2020, any refrigerant leak is now extremely expensive to repair, R-22 costs $50 to $100+ per pound (a full charge is 6 to 16 pounds). A system that uses R-22 and develops a leak is an immediate replacement candidate. All new systems use R-410A or the newer R-454B.
Noise. Grinding, squealing, banging, or rattling that was not there before indicates failing bearings, a cracked heat exchanger, loose components, or compressor failure. Some of these are repairable; others (a cracked heat exchanger on a gas furnace, for example) are replacement triggers because the repair is not cost-effective or the component creates a safety hazard.
Choosing a System: The Decision Framework
All-Electric Home, No Gas Service
Best option: ducted air-source heat pump (or mini-split if no ductwork). A heat pump replaces both the electric furnace and the AC with one system that costs far less to operate than electric resistance heat. The federal tax credit and Maryland rebates make this the most affordable path. Operating cost drops by 40 to 60 percent compared to electric resistance heat.
Home with Natural Gas
Option A: high-efficiency gas furnace + central AC. The traditional setup. Reliable, well-understood, and competitive on operating cost if gas prices stay moderate. No rebates for the AC or furnace unless they meet the highest efficiency tiers.
Option B: dual fuel (heat pump + gas furnace). Uses the heat pump for mild weather and the furnace for deep cold. Operating cost is lower than gas-only for most of the year. The heat pump qualifies for the federal tax credit and state rebates.
Option C: heat pump only. A cold-climate heat pump handles Southern Maryland winters without gas backup. Eliminates the gas bill entirely (if no other gas appliances). Qualifies for the full rebate and credit stack.
Home with Propane
Best option: heat pump. Propane heating is expensive, $1,000 to $1,800 per year for a typical home. A heat pump cuts that to $400 to $700 per year in electricity and eliminates the propane delivery, tank rental, and price volatility. If you heat with propane and cool with central AC, a heat pump replaces both systems and drops your combined heating and cooling cost by 40 to 50 percent.
What to Expect During Installation
A standard HVAC replacement (removing old equipment and installing new using existing ductwork) takes 1 to 2 days. A system change (switching from a furnace and AC to a heat pump, or adding ductwork) takes 2 to 4 days. A full ductwork replacement adds 2 to 3 days.
Day 1: The crew removes the old indoor and outdoor equipment, installs the new indoor unit (furnace or air handler), installs the evaporator coil, and runs the refrigerant lines and electrical connections to the outdoor unit location.
Day 2: The outdoor unit is set on its pad and connected, the refrigerant lines are pressure tested and charged, the thermostat is installed, the system is started up and tested, and the crew cleans up. Permits and inspections are scheduled.
You can stay in the house during the work. You will be without heating and cooling for 4 to 8 hours on the first day while the old system is disconnected and the new system is being connected. In September, that means the house gets warm during the day, plan accordingly.
Ductwork: The Hidden Cost Factor
Your ductwork is the delivery system. A brand-new, perfectly efficient furnace or heat pump connected to leaky, undersized, or deteriorated ductwork will underperform, it is like putting a high-performance engine in a car with flat tires.
Signs your ductwork needs attention:
- Visible damage: disconnected sections, crushed flex duct, rusted metal duct
- Uneven temperatures between rooms
- Excessive dust in the house (a sign of leaks pulling air and debris from unconditioned spaces)
- High energy bills despite a relatively new system
- Ductwork that has never been sealed or insulated (common in crawl spaces and attics in Southern Maryland homes built before 2000)
Duct sealing ($500 to $2,000) closes leaks in the duct joints and connections using mastic sealant or metallic tape (not fabric "duct tape," which deteriorates and fails). This alone can improve system efficiency by 15 to 25 percent.
Duct insulation ($500 to $2,000) wraps the ductwork in insulation to prevent heat loss (in heating mode) or heat gain and condensation (in cooling mode) as air travels through unconditioned spaces. Uninsulated ductwork in a crawl space or attic loses 20 to 30 percent of the heating or cooling energy before it reaches the rooms.
Full ductwork replacement ($3,000 to $8,000) is warranted when the existing ductwork is severely deteriorated, undersized, improperly designed, or cannot be adequately sealed. If you are replacing a 20-year-old HVAC system, the ductwork is probably 20 years old too, evaluate it as part of the replacement decision.
Frequently Asked Questions
How much does it cost to replace an HVAC system in Southern Maryland? A full system (furnace or air handler plus air conditioner or heat pump) costs $5,000 to $16,000 installed. Most homeowners pay $7,000 to $12,000. The cost depends on the system type, efficiency rating, home size, and whether ductwork or electrical modifications are needed. Heat pump systems qualify for $2,000 to $10,000+ in federal tax credits and Maryland rebates, which can bring the effective cost below $5,000.
How long does an HVAC system last? Central air conditioners and heat pumps last 12 to 20 years (median 15). Gas furnaces last 15 to 25 years (median 20). Electric furnaces last 20 to 30 years. Mini-splits last 15 to 20 years. Regular maintenance (annual tune-ups, filter changes every 1 to 3 months) extends lifespan and maintains efficiency. Coastal and high-humidity environments like Southern Maryland shorten outdoor unit lifespan by 1 to 3 years due to salt air and corrosion exposure, particularly for homes closer to the Chesapeake Bay.
Should I replace the furnace and AC at the same time? If both units are near the end of their lifespan (12+ years for AC, 18+ years for furnace), replacing both together is typically $500 to $1,500 cheaper than replacing them separately, because the contractor is already on-site, the refrigerant lines are already being handled, and the coil is matched to both units. Mismatched components (a new AC with an old furnace or vice versa) can reduce efficiency and cause compatibility issues.
Is a heat pump worth it in Southern Maryland? For most Southern Maryland homeowners, yes, particularly with the current rebate and credit structure. A heat pump handles both heating and cooling, operates more efficiently than a gas furnace in mild weather (which is most of the Southern Maryland heating season), eliminates or reduces fossil fuel use, and qualifies for $5,000 to $10,000+ in incentives. The math is strongest for homes currently heating with electric resistance, propane, or oil.
Do I need a permit to replace my HVAC system? Yes. HVAC replacement requires a mechanical permit and inspection in Calvert, St. Mary's, and Charles County. Your contractor handles the permit as part of the job. Replacing an HVAC system without a permit is a code violation that can complicate home sales and insurance claims.
How often should I change the filter? Every 1 to 3 months during the heating and cooling season. In Southern Maryland, where the system runs nearly year-round (cooling from May through September, heating from November through March, and intermittent shoulder-season use in between), change the filter monthly during peak use. A clogged filter restricts airflow, forces the system to work harder, increases energy consumption, and accelerates wear on the blower motor and compressor.
What SEER2 rating should I get? For Southern Maryland, SEER2 16 to 18 offers the best balance of upfront cost and operating savings. Going above SEER2 20 adds significant equipment cost for diminishing returns on annual savings. The exception is mini-splits, where SEER2 ratings of 20 to 30+ are standard because the technology is inherently more efficient.
HVAC system past its prime, or ready to switch to a heat pump and start saving? Gray & Sons Contracting has been keeping Southern Maryland homes comfortable for 50 years. We will size the system properly, walk you through the rebate and credit options, handle the permit, and make sure you have reliable heat before winter. Get a Free Estimate