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Most gas furnaces in homes today give you about 15–20 years of service. ENERGY STAR says to start considering a replacement once the furnace or boiler is over 15 years old, especially if repairs and energy bills are going up.
Recent 2025 cost reports show most homeowners paying somewhere in the $4,000–$8,000 range for a standard furnace replacement, with national averages in the $4,800–$6,200 window for a straightforward gas swap. High-efficiency models, oil units, or installs that need venting/duct changes can push closer to $10,000. Use $5,000–$6,000 as a reasonable planning number for a typical gas furnace replacement.
You do not have to replace a furnace at a specific birthday, but these are the usual triggers:
If the furnace is old and the repair is a large share of a new unit (roughly a quarter to half), replacement is easier to justify.
Older or standard furnaces often operate near 80% AFUE, meaning about 80% of the fuel becomes heat for the home. Current high-efficiency (condensing) gas furnaces reach roughly 90–98% AFUE, but they need proper PVC venting and a condensate drain. Moving from an older 80% unit to a 95% unit means more of every dollar of fuel is turned into heat, which helps offset the higher equipment cost, especially in colder climates.
Getting two quotes from licensed HVAC contractors is the best way to confirm your number.
A normal replacement looks like this:
1. The contractor removes and hauls away the old furnace.
2. The new furnace is set and connected to gas, electrical, condensate (for high efficiency), and venting.
3. Duct or plenum is adjusted so the cabinet seals properly.
4. The system is started, checked for safe operation, and tied to your thermostat.
5. You are shown where the filter goes and how often to change it.
If your old system never had a good filter rack, this is the right time to ask for one, so your new furnace does not pull dusty air around the filter.
A new furnace will stay cleaner and closer to its tested efficiency if the filter fits and is replaced on schedule. Keep a snug pleated filter in place, point the airflow arrow toward the unit, and check monthly. A filter that is too loose or too restrictive will work against the new equipment.
After your new furnace is in, you can keep it clean with properly sized filters. Filterbuy offers pleated HVAC/furnace filters in MERV 8, MERV 11, and MERV 13, in standard and custom sizes, made in the USA, with free shipping. Auto Delivery makes it easier to stay on the change schedule your installer recommends.
Filterbuy HVAC Solutions can install new, properly sized, high-efficiency equipment and make sure the filter rack seals so the new furnace stays clean and efficient.
Most gas furnaces in homes run well for about 15–20 years. After about 15 years, ENERGY STAR says to start looking at replacement, especially if costs or repairs are going up.
If the furnace is older than 15 years and you are facing a major part replacement (heat exchanger, blower, control board), or you’re calling for service every season, replacement is usually the better long-term choice. A new unit will also be more efficient than an old 80% model.
AFUE (Annual Fuel Utilization Efficiency) tells you how much of the fuel becomes heat for the home. Older units are often around 80% AFUE. New high-efficiency gas furnaces can reach about 90–98% AFUE, so more of your fuel bill turns into heat.
Many homeowners in 2025 pay around $4,800–$6,200 for a straightforward gas furnace swap. High-efficiency models, oil furnaces, or installs that need venting and duct changes can move the total toward $7,000–$10,000.
Not always. If the ducts are sized correctly, in good condition, and accessible, a contractor can connect the new furnace to the existing ductwork. If ducts leak or are undersized, the installer may recommend repairs so the new unit can reach its rated efficiency.
The crew removes the old furnace, sets the new one, connects gas, electrical, venting, and condensate (for high-efficiency models), seals to the ductwork, and test-runs the system with your thermostat. You should also be shown the filter location and change schedule.
If you replace an older 80% unit with a properly sized 90–95%+ unit, you should see lower fuel use for the same heating because less energy is wasted in the exhaust. Actual savings depend on your climate and how often the system runs.
You can if it is the correct size and MERV for the new filter rack. A new furnace is a good time to switch to a snug pleated filter so dust does not reach the blower or heat exchanger.
Yes. Filterbuy HVAC Solutions can install a new, properly sized furnace and make sure the filter rack seals so the system stays clean and efficient.
Change filters on schedule, keep returns clear, and have the system serviced yearly. Clean filtration and basic maintenance help high-efficiency furnaces stay close to their tested AFUE.
