Frequently Asked Questions
Answers to Common HVAC Questions From Raleigh Homeowners
Whether you're troubleshooting a problem, planning an upgrade, or just want to understand your HVAC system better, we've organized answers to the questions Raleigh homeowners ask most. Each section covers a different topic — click any category below to jump ahead, or scroll through all 32 answers.
Jump to: Air Conditioning · Heating & Furnaces · Heat Pumps · HVAC General · Ductless Mini-Splits · Indoor Air Quality · Maintenance & Costs · Emergency Service
Air Conditioning
Common questions about central air conditioning systems, efficiency, and cooling technology.
What is the difference between a central air conditioner and a window unit?
A central air conditioner uses ductwork to cool your entire home from a single outdoor unit and indoor evaporator coil. It's quieter, more efficient, and distributes air evenly through every room. Window units cool only the room they're installed in and are less efficient for whole-home cooling.
For most Raleigh homes with existing ductwork, a central AC installation is the better long-term investment. If you only need to cool one room — like a garage workshop or bonus room without ducts — a ductless mini-split is a more efficient alternative to window units.
How does a two-stage or variable-speed AC differ from a single-stage system?
A single-stage AC has one speed — full blast. It cycles on, runs at 100% capacity until your thermostat is satisfied, then shuts off completely. A two-stage system has a low setting (around 65-70% capacity) and a high setting, so it can run longer at lower power on mild days. Variable-speed systems adjust continuously from about 25% to 100% capacity.
The practical difference for Raleigh homeowners: two-stage and variable-speed systems remove more humidity, maintain more even temperatures, run more quietly, and use less energy. They cost more upfront but typically pay for themselves through lower utility bills. Ask about efficiency options during your AC installation consultation.
Can my AC system also control humidity, or do I need a separate dehumidifier?
Your AC does remove some humidity as a byproduct of cooling — moisture condenses on the cold evaporator coil and drains away. However, in Raleigh's humid subtropical climate (especially during the muggy shoulder seasons of April-May and September-October), your AC alone may not keep indoor humidity below the ideal 40-50% range.
If you notice condensation on windows, a musty smell, or the air feels clammy even when the AC is running, a whole-house dehumidifier integrated with your HVAC system is the most effective solution. It works independently of your AC, so it can control humidity even when cooling isn't needed.
What does the new R-454B (A2L) refrigerant transition mean for my existing AC?
As of January 2025, all newly manufactured residential AC systems and heat pumps use R-454B refrigerant instead of R-410A. R-454B has 78% lower global warming potential, which is why the EPA mandated the switch under the AIM Act.
If your current system uses R-410A, it will continue to work normally — R-410A is still available for repairs and recharges. You don't need to replace your system. However, when it's time for a new unit, your next AC installation will use R-454B. The new refrigerant requires slightly different handling and equipment, so make sure your technician is trained on A2L systems. Our team is already certified for R-454B installations and AC repairs on both refrigerant types.
Heating & Furnaces
Questions about furnace types, heating efficiency, and keeping your Raleigh home warm through winter.
What is the difference between a gas furnace and an electric furnace for Raleigh homes?
A gas furnace burns natural gas to produce heat and is the most common heating system in the Triangle. It heats air faster, reaches higher output temperatures, and typically costs less to operate because natural gas is cheaper than electricity per BTU in North Carolina.
An electric furnace uses heating elements (like a large toaster) and requires no gas line, making it simpler to install. Electric furnaces are 100% efficient at converting electricity to heat, but electricity costs more per unit of energy, so monthly bills are usually higher. For homes without a natural gas connection, a heat pump is often a more efficient electric heating option than a straight electric furnace.
Why does my furnace smell when I first turn it on in the fall?
A brief burning or dusty smell when you first run your furnace after months of sitting idle is normal. Dust settles on the heat exchanger and burner assembly over the summer, and it burns off during the first few heating cycles. This smell should go away within a few hours.
If the smell persists beyond one day, smells like rotten eggs (natural gas additive), or you notice a metallic or electrical burning odor, turn off your furnace and call for furnace repair immediately. Persistent smells can indicate a cracked heat exchanger, electrical fault, or gas leak — all of which require professional diagnosis. Annual furnace maintenance before heating season catches these issues early.
Should I close air vents in rooms I do not use to save energy?
No — this is one of the most common HVAC myths. Closing vents doesn't reduce energy consumption. Your furnace and blower are sized for your entire home's ductwork. When you close vents, it increases static pressure in the duct system, forcing the blower to work harder, which wastes energy and can damage components over time.
Closed vents also create pressure imbalances that can cause air leaks in ductwork, increase heating costs in the rooms that are open, and even lead to condensation and mold in the closed-off rooms. Instead of closing vents, consider a professional HVAC assessment to optimize your system's airflow, or ask about zone-controlled systems if some rooms consistently overheat while others stay cold.
What is a two-stage or modulating furnace and is it worth the extra cost?
A single-stage furnace operates at full capacity every time it fires. A two-stage furnace has a low-fire setting (around 60-65% capacity) and a high-fire setting, running on low most of the time and ramping up only on the coldest days. A modulating furnace adjusts its flame in small increments — typically between 40% and 100% — to precisely match your home's heating demand.
For Raleigh's climate, a two-stage or modulating furnace provides noticeably better comfort: fewer temperature swings, quieter operation, and better humidity control during mild winter days. The energy savings range from 10-20% compared to single-stage models. Whether the upgrade is worth it depends on your home size, insulation quality, and how long you plan to stay. Our technicians can help you weigh the options during a furnace installation consultation.
Heat Pumps
How heat pumps work, performance in Raleigh winters, and whether one is right for your home.
Can a heat pump replace both my air conditioner and furnace?
Yes. A heat pump is a single system that provides both cooling in summer and heating in winter by reversing the direction of refrigerant flow. In cooling mode it works identically to an air conditioner; in heating mode it extracts heat from outdoor air and moves it inside.
Modern heat pumps are highly effective in Raleigh's climate, where winter temperatures rarely stay below freezing for extended periods. However, during extreme cold snaps (below 25-30°F), a heat pump's output decreases and supplemental heat kicks in. Many homeowners choose a dual fuel system that pairs a heat pump with a gas furnace backup for the coldest nights — giving you the efficiency of a heat pump for 90% of the year and gas heat when you need it most. Learn more about your options with a heat pump installation consultation.
How does a heat pump perform during a Raleigh ice storm or power outage?
During an ice storm, a heat pump can experience ice buildup on the outdoor coil. This is normal — the system has a defrost cycle that periodically reverses the refrigerant to melt accumulated ice. However, heavy ice accumulation or blocked airflow around the outdoor unit can overwhelm the defrost cycle. Keep the area around your outdoor unit clear of snow, ice, and debris.
During a power outage, a heat pump will not operate at all — it's fully electric. Unlike a gas furnace (which also needs electricity for the blower and controls), there is no partial-function mode. If power outages are a concern, consider a whole-home generator or a dual fuel system with a gas furnace backup. For heat pump issues during or after a storm, our team offers emergency heat pump service 24/7.
What is the difference between an air-source heat pump and a geothermal heat pump?
An air-source heat pump extracts heat from outdoor air (even in cold weather) and is the most common type installed in the Raleigh area. It uses a standard outdoor unit similar to an air conditioner and is relatively affordable to install.
A geothermal (ground-source) heat pump extracts heat from underground, where temperatures stay around 55°F year-round in North Carolina. Because the ground temperature is more stable than air temperature, geothermal systems are 30-50% more efficient. However, they require boring wells or trenching loops into your yard, which makes installation significantly more expensive — typically $15,000-$30,000 more than air-source.
For most Raleigh homeowners, an air-source heat pump installation offers the best balance of efficiency, comfort, and cost. Geothermal makes more sense for larger properties where you can amortize the installation cost over decades of lower utility bills.
Do heat pumps increase my electric bill compared to a gas furnace?
Your electricity bill will go up because the heat pump uses electricity to heat your home instead of gas. But your gas bill will drop to near zero (just the meter charge). The net result — your total energy cost — depends on local utility rates and the efficiency of both systems.
In the Raleigh-Durham area, a modern high-efficiency heat pump (HSPF2 of 9+) typically costs about the same or slightly less to operate annually than a mid-efficiency gas furnace (80% AFUE), considering current Duke Energy and Dominion gas rates. If you're comparing to a high-efficiency gas furnace (95%+ AFUE), the gas furnace usually wins on operating cost by a small margin. The gap narrows if you qualify for heat pump tax credits or utility rebates. Talk to us about a cost comparison specific to your home during a heat pump service visit or consultation.
HVAC General
Broad questions about HVAC systems, choosing a contractor, efficiency ratings, and when to repair versus replace.
How do I choose the right HVAC company in Raleigh?
Start by verifying licensing — every HVAC company in North Carolina must hold a valid license from the NC Board of Examiners of Plumbing, Heating and Fire Sprinkler Contractors. Ask for the license number and look it up. Then check for NATE-certified technicians, which means the people working on your system have passed rigorous industry exams.
Beyond credentials, look for a company with strong Google and Yelp ratings (hundreds of reviews, not just a handful), proper insurance, and a willingness to provide written estimates before starting work. A company that offers maintenance plans and stands behind its work with clear service guarantees is a good sign of long-term reliability.
What should I expect during an HVAC service call?
A typical service call takes 1-2 hours. The technician will start with a visual inspection of your indoor and outdoor equipment, then run diagnostic tests — checking electrical connections, refrigerant levels, airflow, and thermostat calibration. They'll identify the issue and give you a written estimate before doing any repairs.
Diagnostic fees in the Raleigh area typically range from $75-$150. This fee usually gets applied toward the repair cost if you proceed. Before the visit, note any symptoms (unusual noises, temperature inconsistencies, error codes on your thermostat) — this helps the technician diagnose faster. You can schedule a service call online or by phone at (919) 673-7667.
How do I know when it is time to replace my HVAC system rather than repair it?
Consider the “5,000 rule”: multiply the repair cost by the age of your system. If the result exceeds $5,000, replacement is usually the smarter financial choice. Other strong indicators include: your system is 15+ years old, repairs are becoming more frequent (two or more per year), energy bills keep rising despite maintenance, or your system uses R-22 refrigerant (phased out and increasingly expensive).
A new high-efficiency system can cut energy consumption by 30-50% compared to a unit from the early 2000s. Federal tax credits and manufacturer rebates can offset a significant portion of the upfront cost. If you're on the fence, schedule an HVAC inspection — we'll assess your system's condition honestly and help you weigh repair versus replacement options.
What does NATE certification mean and why should I care?
NATE stands for North American Technician Excellence — it's the leading certification program for HVAC technicians in the United States. Technicians earn NATE certification by passing rigorous written exams covering installation, service, and system knowledge. It's voluntary and goes beyond the minimum state licensing requirements.
Why it matters: NATE-certified technicians have demonstrated competency that's been independently verified. Studies show they have higher first-visit repair success rates, which means your problem is more likely to be fixed correctly the first time. When choosing an HVAC company, ask whether their technicians are NATE-certified — it's one of the clearest indicators of technical skill.
What do SEER, SEER2, AFUE, and HSPF ratings mean and which ones matter?
SEER / SEER2 (Seasonal Energy Efficiency Ratio) measures cooling efficiency. Higher is better — the federal minimum is SEER2 13.4 for Raleigh (South region). Most mid-range units are 15-17 SEER2; premium units reach 20+. This is the rating that matters when comparing air conditioners.
AFUE (Annual Fuel Utilization Efficiency) measures furnace heating efficiency as a percentage — an 80% AFUE furnace converts 80% of gas to heat. High-efficiency models reach 95-98% AFUE. This matters when comparing furnaces.
HSPF / HSPF2 (Heating Seasonal Performance Factor) measures heat pump heating efficiency. The federal minimum is HSPF2 7.5; high-efficiency models reach 10+. This matters when comparing heat pumps.
In short: use SEER2 for cooling comparisons, AFUE for furnace comparisons, and HSPF2 for heat pump heating comparisons. Higher numbers always mean lower operating costs.
Ductless Mini-Splits
Questions about ductless mini-split systems, their efficiency, and where they work best.
Are ductless mini-splits more energy efficient than central air conditioning?
On a per-unit basis, ductless mini-splits are typically more efficient than central AC systems because they eliminate duct losses. The Department of Energy estimates that ductwork can lose 20-30% of conditioned air through leaks, poor connections, and heat transfer through uninsulated duct walls. Mini-splits deliver conditioned air directly into the room with no duct losses.
However, if you need to cool your entire home, multiple mini-split heads (a multi-zone system) can approach or exceed the cost of a central AC system. Mini-splits excel in specific scenarios: additions, converted garages, sunrooms, or older homes without existing ductwork. For homes that already have good ductwork, central AC is usually more cost-effective to install for whole-home cooling. Learn about your options with a mini-split installation consultation.
Can I add a mini-split to a room where I cannot run ductwork?
Yes — this is exactly what ductless mini-splits were designed for. The indoor unit mounts on a wall (or ceiling), and a small conduit (about 3 inches in diameter) connects it to the outdoor unit through an exterior wall. No bulky ductwork, no major construction.
Common applications in Raleigh-area homes include: finished attics and basements, garage conversions, sunrooms, home offices, and historic homes where cutting duct chases would damage original architecture. A single-zone mini-split system can heat and cool one room independently from your central system, giving you precise temperature control where you need it.
How visible are ductless mini-split indoor units and can they be concealed?
The standard wall-mounted indoor unit is about 32 inches wide, 12 inches tall, and 8 inches deep — roughly the size of a small shelf. It's mounted high on the wall near the ceiling. Modern units from brands like Daikin, Mitsubishi, and Carrier have sleek designs that blend in reasonably well, but they are visible.
If aesthetics are a priority, there are alternatives: ceiling cassette units mount flush in the ceiling with only a small grille visible, floor-standing units sit at baseboard level, and slim duct units can be concealed in a small soffit or closet. These options cost more and require more installation work, but they're nearly invisible. Discuss the options with our team during your mini-split installation consultation.
Indoor Air Quality
How your HVAC system affects the air you breathe — filtration, humidity, allergens, and safety.
How do I know if my home has a carbon monoxide risk from my HVAC system?
Any fuel-burning appliance — gas furnaces, gas water heaters, gas dryers — can produce carbon monoxide (CO) if they malfunction. The primary risk in HVAC systems is a cracked heat exchanger in a gas furnace, which can leak combustion gases (including CO) into your home's air supply.
Warning signs include: persistent headaches or flu-like symptoms that improve when you leave the house, a yellow or flickering pilot light (instead of steady blue), soot or scorch marks around your furnace, and excess condensation on windows near the furnace. Every home with gas appliances should have CO detectors on each level. For peace of mind, schedule an air quality inspection or annual furnace maintenance — our technicians specifically test for heat exchanger integrity and CO levels.
What is the best indoor humidity level for Raleigh homes year-round?
The EPA and ASHRAE recommend maintaining indoor relative humidity between 30-50%, with 40-45% being the sweet spot for comfort and health. In Raleigh, the challenge shifts with the seasons:
Summer (May-September): Outdoor humidity often exceeds 70-80%. Your AC removes some moisture, but a whole-house dehumidifier may be needed to stay below 50% — especially during mild, humid days when the AC doesn't run long enough to dehumidify adequately.
Winter (December-February): Heated indoor air can drop below 30% humidity, causing dry skin, static electricity, cracked woodwork, and increased respiratory infections. A whole-house humidifier integrated with your furnace adds moisture automatically to maintain comfort.
Can my HVAC ductwork be making my allergies worse?
Absolutely. Leaky ductwork running through attics, crawl spaces, and wall cavities can pull in dust, insulation fibers, mold spores, and even pest droppings — then distribute them through every room in your home. Even well-sealed ducts accumulate dust, pollen, and allergens over time, especially during Raleigh's heavy pollen season (March-May).
If you or family members notice allergy symptoms that worsen when the HVAC runs, visible dust blowing from vents, or musty odors when the system starts, your ductwork may need attention. Professional duct sealing eliminates leaks that pull in contaminants, and duct cleaning removes accumulated buildup. An air quality inspection can identify whether your ducts are contributing to your symptoms.
What is a MERV rating and what filter should I use for my home?
MERV (Minimum Efficiency Reporting Value) rates how effectively an air filter captures particles on a scale of 1-20. Higher ratings catch smaller particles. For residential HVAC systems, the sweet spot is typically MERV 11-13:
MERV 8: Catches dust, pollen, and lint. The bare minimum for residential systems. Adequate if nobody in the house has allergies or respiratory issues.
MERV 11-13: Catches everything MERV 8 does plus mold spores, pet dander, fine dust, and some bacteria. Recommended for most Raleigh homes, especially during pollen season. This is what we install for our maintenance plan customers.
MERV 14+: Hospital-grade filtration. Catches very fine particles but can restrict airflow in residential systems not designed for it. Using too high a MERV rating can strain your blower motor and reduce efficiency — always check your system's specifications or ask your technician. For advanced filtration without airflow restriction, consider a whole-house air purifier installed in your ductwork.
Maintenance & Costs
What HVAC service costs, how to maintain your system, and whether maintenance plans are worth it.
How often should I replace my HVAC air filter?
Standard 1-inch filters should be replaced every 30-90 days, depending on conditions. Homes with pets, smokers, or allergy sufferers should lean toward the 30-day end. Thicker media filters (4-5 inches) typically last 6-12 months.
In Raleigh, seasonal factors matter: during March-May pollen season and peak summer usage (June-August), check your filter monthly. A dirty filter forces your system to work harder, reduces airflow, increases energy consumption by up to 15%, and can lead to frozen evaporator coils or compressor strain. Regular filter changes are the single most impactful thing homeowners can do between professional HVAC maintenance visits. Our Comfort Club members receive filter reminders and priority scheduling.
How much does an average HVAC service call cost in the Raleigh area?
A diagnostic service call in the Raleigh-Durham area typically runs $75-$150 for the visit and diagnosis. This covers the technician's travel time, initial inspection, and assessment of the problem. Most reputable companies apply the diagnostic fee toward the repair cost if you proceed with the work.
Repair costs vary widely depending on the issue: a capacitor replacement might be $150-$300 total, a blower motor $400-$700, a compressor $1,500-$2,500, and a heat exchanger $1,500-$3,000. For routine tune-ups (non-emergency preventive maintenance), expect $75-$200 per unit. Maintenance plan members typically receive discounted rates on both tune-ups and repairs, plus priority scheduling during peak season.
Is an HVAC maintenance plan worth the money?
For most homeowners, yes — especially if your system is more than a few years old. A maintenance plan typically includes two professional tune-ups per year (spring for AC, fall for heating), priority scheduling during peak season, and discounted repair rates. Many plans also include no overtime charges for emergency calls.
The financial case: a single emergency repair during a July heatwave can easily cost $300-$500 more than the same repair scheduled during a slow period, between the overtime fees and emergency dispatch charges. Regular maintenance also extends equipment lifespan by 3-5 years and reduces the likelihood of breakdowns by catching small issues before they escalate. Our Comfort Club and maintenance packages are designed specifically for Raleigh homeowners who want to protect their investment without worrying about surprise costs.
What can I do myself to maintain my HVAC system between professional visits?
There are several things homeowners can do to keep their HVAC system running well between annual tune-ups:
Monthly: Check and replace your air filter (the single most impactful DIY task). Keep supply and return vents clear of furniture, rugs, and curtains.
Seasonally: Clear debris (leaves, grass clippings, mulch) from around the outdoor unit — maintain at least 2 feet of clearance on all sides. Rinse the outdoor coil gently with a garden hose. Check your thermostat batteries and settings when switching between heating and cooling seasons.
Annually: Visually inspect exposed ductwork in your attic or crawl space for obvious gaps or disconnections. Test your CO detectors. Clear your condensate drain line by flushing it with a cup of white vinegar (prevents clogs and water damage).
Leave the technical work — refrigerant checks, electrical testing, combustion analysis, and blower calibration — to a professional during your annual scheduled tune-up.
Emergency Service
When to call for emergency HVAC help, what to expect, and how to handle urgent situations like gas leaks.
When should I call for emergency HVAC service instead of scheduling a regular repair?
Call immediately (true emergencies): You smell gas or rotten eggs near your furnace (leave the house first, then call). You hear hissing from a gas line. You see sparks, smoke, or a burning smell from your HVAC equipment. Your system has completely failed during extreme heat (above 95°F) or cold (below 25°F), especially with children, elderly, or medically vulnerable household members.
Can wait for regular scheduling: Uneven temperatures between rooms. Minor or intermittent noises. Gradually rising energy bills. One zone not reaching set temperature. A system that's working but not as well as it used to.
Our technicians provide emergency AC service and emergency heating service 24 hours a day, 7 days a week. Call (919) 673-7667 any time — we'll help you determine whether your situation needs immediate attention or can be safely scheduled for the next available appointment.
Does emergency HVAC service cost more than a regular appointment?
Yes, typically. Emergency and after-hours service calls often include additional fees compared to standard business-hours appointments. This can include overtime labor rates (usually 1.5x the standard rate), after-hours dispatch charges, and priority scheduling premiums.
That said, some HVAC companies — including those with maintenance plans — waive overtime charges for plan members. If you're on a maintenance plan, check your agreement for emergency service terms before assuming you'll pay extra. For non-emergency issues discovered in the evening or weekend, it's usually more cost-effective to schedule a regular appointment for the next business day rather than requesting same-day emergency service.
What should I do if I smell gas coming from my furnace?
This is a true emergency — follow these steps in order:
1. Do not turn on or off any lights, appliances, or electrical switches. Do not use your phone inside the house. Do not light any flames.
2. Open windows and doors if you can do so quickly and safely while exiting.
3. Leave the house immediately with all household members and pets.
4. Call 911 or your gas company from outside the house or from a neighbor's phone. Dominion Energy NC's emergency line is 1-877-776-2427.
5. Do not re-enter until the gas company or fire department has confirmed it's safe.
After the gas company has cleared the home and shut off the supply if needed, call us for emergency furnace service to inspect, diagnose, and repair the issue before you resume using your heating system. Gas leaks can originate from loose connections, cracked heat exchangers, or faulty gas valves — all of which require professional HVAC repair.
How quickly can an HVAC technician arrive for an emergency in the Raleigh area?
Response times vary depending on the time of day, season, and current demand. During business hours in the off-season, same-day service is typically available — often within a few hours of your call. During peak summer and winter seasons, especially on weekends and evenings, response times may be longer due to high call volume.
As a general guide: for true safety emergencies (gas leaks, electrical hazards, CO detector alarms), technicians prioritize these calls and aim for the fastest possible response. For comfort emergencies (complete system failure during extreme weather), most calls are addressed within 2-6 hours during business hours or by the next morning for late-night calls.
Our Comfort Club members receive priority scheduling, which moves them to the front of the queue. Call (919) 673-7667 for emergency service — our dispatcher will give you an estimated arrival time based on current availability.
Still Have Questions?
Our HVAC experts are happy to answer any question — no pressure, no obligation. Call or schedule online.
