How do I find out what type of heating system my home has?

Look at the equipment in your utility area, typically a basement, closet, garage, or attic. A furnace is a large metal box with ductwork running from it. A boiler is a large metal unit connected to pipes, not ducts, feeding radiators or baseboard heaters. A heat pump looks like a central air conditioner outside with an indoor air handler. Check the equipment label for the manufacturer, model number, fuel type, and installation date. Your home inspection report from purchase will also identify the system. If you still cannot tell, an HVAC technician can identify it during a routine maintenance visit.

How often should I change my HVAC filter?

ENERGY STAR recommends checking your filter every month during heavy-use seasons (winter and summer) and changing it at minimum every three months. A dirty filter restricts airflow, forces the system to work harder, increases energy costs, and can lead to equipment damage. The correct replacement interval depends on your filter type, household size, whether you have pets, and how much the system runs. One-inch fiberglass filters may need monthly replacement. Four-inch pleated filters can last three to six months. Check monthly, and replace when the filter looks gray or clogged.

What is the difference between AFUE and SEER ratings?

AFUE (Annual Fuel Utilization Efficiency) measures heating efficiency for furnaces and boilers. It tells you what percentage of fuel becomes usable heat. A 95 percent AFUE furnace converts 95 cents of every fuel dollar into heat. The current federal minimum is 80 percent AFUE for gas furnaces, with a 95 percent minimum taking effect for new installations in northern regions by 2029. SEER (Seasonal Energy Efficiency Ratio) measures cooling efficiency for air conditioners and heat pumps. Higher numbers mean more efficient cooling. The current federal minimum is 15 SEER2 in northern regions and 16 SEER2 in southern regions for central air conditioners.

Will my heating system work during a power outage?

Most modern heating systems require electricity to operate, even if the fuel source is gas, oil, or propane. Gas furnaces need electricity for the blower motor, ignition system, and controls. Boilers need electricity for the circulator pump and controls. Heat pumps are entirely electric. A wood stove or fireplace with a direct-vent design can provide heat without electricity, but a wood stove with a blower relies on electricity for air distribution. A portable generator can power a furnace if properly sized, but generators must be operated outdoors and connected safely. Our heating during outages guide covers backup heating options in detail.

When should I replace my heating or cooling system?

Furnaces typically last 15 to 20 years, boilers 15 to 30 years, air conditioners 15 to 20 years, and heat pumps 10 to 15 years. Consider replacement when repair costs exceed half the cost of a new system, when the system can no longer maintain comfortable temperatures, when utility bills are rising without explanation, when the system runs constantly or cycles frequently, or when the equipment has been repaired multiple times in the past two years. If your system is approaching or past its expected lifespan, start planning and budgeting for replacement before it fails during extreme weather.

Heating and Cooling Systems: Know What Keeps Your Home Comfortable

Starting Point

What type of system do you have?

Nearly half the energy used in a typical U.S. home goes to heating and cooling.^[1] The system that uses that energy sits in your basement, utility closet, garage, or attic. Knowing what it is, how it works, and what it needs is the most basic form of energy literacy.

Forced-air furnace

The most common heating system in the U.S., found in roughly 60 million homes. Burns gas, propane, oil, or uses electricity to heat air, then pushes it through ductwork with a blower. You will see a large metal cabinet with ductwork running from it, a filter slot, and (for gas units) a gas line connected to it.

Fuels: natural gas (most common), propane, heating oil, electricity

Boiler (hydronic)

Heats water instead of air. Hot water circulates through pipes to radiators, baseboard heaters, or radiant floor systems. You will see a large unit with pipes (not ducts) running from it, and radiators or baseboard units in the rooms. More common in older homes and in the Northeast.

Fuels: natural gas, propane, heating oil, electricity

Heat pump

Moves heat rather than generating it. In winter, extracts heat from outdoor air (or the ground) and moves it inside. In summer, reverses to cool. Looks like a central AC outdoor unit paired with an indoor air handler. Increasingly popular because one system handles both heating and cooling.

Fuel: electricity only. Some paired with gas furnace (dual-fuel/hybrid)

Ductless mini-split

A type of heat pump with individual wall-mounted units in each room or zone, connected to an outdoor compressor by refrigerant lines rather than ductwork. Common in homes without existing duct systems, additions, and converted spaces.

Fuel: electricity only

Wood stove or fireplace

Burns wood or pellets for heat. A wood stove is a standalone unit connected to a chimney or flue pipe. A fireplace insert fits inside an existing masonry fireplace. May be the primary heat source in some homes or a supplemental source in others.

Fuel: cordwood, compressed wood pellets, or manufactured logs

Electric resistance heat

Baseboard heaters, wall heaters, or ceiling cable systems that convert electricity directly into heat. Simple, no ductwork needed, and inexpensive to install. Operating cost is higher than heat pumps because resistance heating converts electricity to heat at a 1:1 ratio rather than moving existing heat.

Fuel: electricity only

Find your equipment label

Every heating and cooling unit has a metal data plate or label on the cabinet. It lists the manufacturer, model number, serial number, fuel type, BTU input and output, and often the installation date. Write this information down and keep it with your household records. When you call for service, the technician will ask for the model number first.

Fuel Sources

What fuel does your system use?

The fuel your system burns determines your supply chain, your vulnerabilities during disruptions, and your backup options. Each fuel has a different delivery method, storage requirement, and failure mode.

Natural gas

Delivered continuously through underground pipelines. You do not store it. It arrives as you use it. This means your supply depends on the gas distribution system, which is generally reliable but can be disrupted by earthquakes, excavation damage, or system-wide pressure loss. If gas service is interrupted, a utility technician must physically relight pilot lights and inspect connections at each home before restoring service to the neighborhood.

Know where your gas shutoff valve is. Our utility shutoffs guide covers this.

Propane (LP gas)

Stored in a tank on your property, typically 120 to 1,000 gallons for residential use. Delivered by truck on a schedule or when you call. Your supply is finite and visible: you can read the gauge on the tank. The vulnerability is running out between deliveries, especially during cold snaps when demand surges and delivery trucks are overbooked.

Our propane basics guide covers tank sizing, safety, and storage.

Heating oil

Stored in a tank, typically 275 gallons, in the basement or buried outside. Delivered by truck. Common in the Northeast. Like propane, your supply is finite. A 275-gallon tank burns through fuel quickly in deep winter. Monitor your gauge and schedule deliveries before the tank drops below one-quarter full. Running empty can introduce air into the fuel line, which requires a service call to bleed and restart the system.

Electricity

Powers heat pumps, mini-splits, electric furnaces, electric boilers, and resistance heaters. Your supply depends entirely on the electrical grid. During a power outage, all-electric heating stops completely. This makes electric-only homes the most dependent on grid reliability and the most in need of a backup heating plan.

Our power outage action plan covers what to do first.

Wood and pellets

Stored on your property. Cordwood needs seasoning (6 to 12 months of drying) and covered storage. Pellets are sold by the bag or ton and need dry storage. The supply chain is local: sawmills, firewood dealers, and pellet distributors. Wood heat is the only common residential fuel source that works entirely without electricity (assuming a non-electric stove without a blower). Our wood heat guide covers stove selection, safety, and fuel management.

Cooling

How your cooling system works

Most homes cool with either a central air conditioning system or a heat pump running in cooling mode. Both use the same basic mechanism: a compressor circulates refrigerant between an indoor evaporator coil and an outdoor condenser coil, moving heat from inside to outside.

Central air conditioning

An outdoor compressor/condenser unit paired with an indoor evaporator coil, usually mounted on top of the furnace. Uses the furnace's blower and ductwork to distribute cooled air. Powered entirely by electricity. The outdoor unit needs clear airflow around it: keep vegetation, debris, and stored items at least two feet away from all sides.

Heat pump (cooling mode)

A heat pump cools the same way an air conditioner does. The difference is that it can reverse the process to heat in winter. If your home has a heat pump, you have one system for both seasons. The outdoor unit looks identical to a central AC unit.

Window units and portable ACs

Self-contained cooling units for individual rooms. Less efficient than central systems but useful for homes without ductwork, for supplemental cooling in specific rooms, or as a backup if the central system fails. Keep the filter clean and ensure the unit is properly sealed in the window to prevent hot air infiltration.

Evaporative coolers (swamp coolers)

Common in dry climates (the Southwest and parts of the Mountain West). They cool air by passing it through wet pads, which cools through evaporation. They use far less electricity than refrigerant-based systems but only work effectively when humidity is low. They add moisture to the air, which is a benefit in arid climates and a drawback in humid ones.

Efficiency

What the efficiency ratings actually mean

Efficiency ratings tell you how much of the energy input becomes useful heating or cooling output. Higher numbers mean lower operating costs. These ratings appear on the equipment label and in product specifications.

Rating	Applies to	What it measures	Federal minimum
AFUE	Furnaces, boilers	Percentage of fuel converted to heat	80% (gas furnace); 95% in northern regions by 2029
SEER2	Central AC, heat pumps (cooling)	Cooling output per watt over a season	15 SEER2 (North), 16 SEER2 (South)
HSPF2	Heat pumps (heating)	Heating output per watt over a season	7.5 HSPF2
EER2	Window units, portable ACs	Cooling output per watt at a single temperature	Varies by capacity

A 95 percent AFUE furnace converts 95 cents of every fuel dollar into heat. The remaining 5 cents is lost as exhaust. The difference between an 80 percent and 95 percent furnace is roughly a 15 percent reduction in fuel use for the same amount of delivered heat.

Maintenance

The maintenance your system needs

ENERGY STAR recommends professional pre-season checkups: cooling equipment inspected in spring, heating equipment in fall. Between those visits, the homeowner's job is filter changes, keeping the outdoor unit clear, and watching for warning signs.^[2]

What you do (monthly and seasonal)

Check and change the filter

Check monthly during heavy-use months. Replace at minimum every three months. A dirty filter restricts airflow, raises energy costs, and can damage the equipment. This is the single most impactful maintenance task a homeowner can do.^[1]

Clear the outdoor unit

Keep at least two feet of clearance around the outdoor condenser or heat pump unit. Remove leaves, grass clippings, and debris. Trim vegetation that encroaches. Restricted airflow forces the compressor to work harder and shortens its life.

Check the condensate drain

Air conditioners and high-efficiency furnaces produce condensate that drains through a tube. If the tube clogs, water can back up and cause damage. Check that the drain line is flowing freely and not blocked by algae or debris.

Check vents and registers

Make sure supply and return vents are not blocked by furniture, rugs, or curtains. Blocked vents create pressure imbalances, reduce efficiency, and can cause the system to short-cycle.

What a technician does (annually)

Professional inspection

A trained HVAC technician inspects electrical connections, measures voltage and current on motors, lubricates moving parts, checks refrigerant levels (cooling systems), inspects the heat exchanger (furnaces), and tests safety controls. This is not a DIY task.^[2]

What to expect in cost

A single maintenance visit typically costs $100 to $200. Annual maintenance plans from HVAC companies, which include one or two visits plus priority service and discounts on repairs, typically run $150 to $500 per year. This is far less than the cost of an emergency repair call or premature system replacement.

Boiler-specific maintenance

Boilers need annual inspection of the pressure relief valve, expansion tank, circulator pump, and water level. Radiators may need to be bled (releasing trapped air) at the start of each heating season to maintain even heat distribution.

Wood stove and chimney

Have the chimney and flue inspected and cleaned at least once a year, preferably before heating season. Creosote buildup is a leading cause of chimney fires. The NFPA recommends annual inspection by a certified chimney sweep.^[3]

Planning Ahead

How long it lasts and when to replace

Equipment	Typical lifespan	Replacement cost range
Gas furnace	15 to 20 years	$3,000 to $8,000 installed
Boiler	15 to 30 years	$4,000 to $12,000 installed
Central air conditioner	15 to 20 years	$3,500 to $8,000 installed
Heat pump	10 to 15 years	$4,000 to $10,000 installed
Wood stove	20 to 40 years	$1,500 to $5,000 installed

Signs it is time to plan for replacement

Repair costs are approaching half the cost of a new system.
The system can no longer maintain comfortable temperatures in extreme weather.
Utility bills are rising without a corresponding increase in rates or usage.
The system runs constantly, cycles on and off frequently, or makes unusual noises.
You have had two or more repair calls in the past year.
The equipment is past its expected lifespan and parts are becoming difficult to source.

Replacement is best planned during mild weather, not in the middle of a heat wave or cold snap when contractors are overwhelmed and prices may be higher. Start getting estimates when your system reaches 75 percent of its expected lifespan.

Preparedness Connection

Why this knowledge matters when the power goes out

Every heating system except a non-electric wood stove requires electricity to operate. Even gas and oil furnaces need electricity for the blower, ignition, and controls. This is the single most important fact about heating and preparedness: a power outage is a heating outage for most homes, regardless of fuel type.

Knowing your system is the prerequisite for every backup plan. If you have a gas furnace, you know a generator of sufficient size can power the blower and controls. If you have a heat pump, you know the power draw is higher. If you have a boiler, you know the circulator pump is what needs power. If you have a wood stove, you know you have a heating option that works without the grid.

Record your system details

In your household binder or utility map, record: system type, fuel source, manufacturer and model number, installation date, HVAC contractor name and phone number, and the wattage required to run the system (found on the equipment label or in the manual). This last number determines whether your generator or battery backup can power the system.

Know your backup options

Our heating during outages and cooling during outages guides cover what to do when the power goes out and your primary system stops. Our passive heating and cooling guide covers techniques that work without any equipment at all.

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