A 20-year-old furnace typically operates at 60% to 80% efficiency (measured by AFUE). This means up to 40% of the energy you pay for is wasted. By contrast, modern high-efficiency furnaces achieve 90% to 98% efficiency, which can significantly lower your monthly utility bills.
Most furnaces are built to last 15 to 20 years with regular maintenance. So, if your furnace has hit the 20-year mark, it may still be operational, but the question is, how well is it functioning? Over time, furnaces lose efficiency. A 20-year-old furnace likely doesn't heat as evenly or efficiently as a newer model.
The $5,000 rule is a guideline to help homeowners decide whether to repair or replace their HVAC system. You multiply the age of your unit by the cost of the needed repair. If that number exceeds $5,000, replacing your HVAC system is often more cost-effective.
Most furnaces installed 20 years ago operate at around 60 to 80 percent efficiency. That means a large portion of the fuel you pay for is wasted instead of being converted into heat. Modern furnaces, by comparison, often operate at 90 percent efficiency or higher.
The reality is that furnace replacement costs in California can vary dramatically – we're talking anywhere from $3,500 to $12,000 or even more in some cases, with Bay Area pricing typically running 20-30% higher than national averages.
5 Warning Signs It's Time for Furnace Replacement
The following are the most costly parts to fix or replace:
When choosing a furnace, the best brand depends on what you prioritize: reliability, high-end efficiency, or budget-friendly value. Based on industry consensus and consumer ratings, the top three furnace brands are Carrier, Trane, and Lennox.
Yes HVAC prices have steadily increased over the past few years, and 2026 is no exception. These increases are affecting everything from entry-level systems to high-efficiency units, making it more expensive than ever to install or replace HVAC systems.
The heat exchanger is often considered the most costly part of a furnace to repair or replace. It is a critical component that transfers heat from the combustion process to the air that circulates throughout your home. Over time, heat exchangers can crack due to the constant heating and cooling cycles they undergo.
The best time to buy a furnace is during the off-season, specifically late spring (April-May) or early autumn (September-October), when HVAC companies are less busy and offer lower prices, rebates, or promotions. Purchasing in these shoulder seasons ensures faster installation times and better negotiating power compared to winter peak season.
Furnace Tax Credit Amounts and Limits for 2025
Federal HVAC tax credits allow homeowners to claim a maximum annual credit of up to $3,200 for qualifying HVAC upgrades made between 2023 and 2025.
Most 2,000-square-foot homes need a furnace between 50,000 and 65,000 BTUs, depending on climate and insulation. Colder regions or older homes may need more heating power, while well-insulated houses in mild climates may need less.
Yes, furnaces can last 30 years, especially Electric Furnaces and high-quality gas units How Long Does A Furnace Last - Carrier. However, the average lifespan is 15–20 years How Long Does A Furnace Last - Carrier. Passing the 30-year mark depends heavily on several factors:
High-efficiency furnaces may require more frequent check-ups by qualified technicians to maintain their optimal performance levels. Additionally, when repairs are needed, they can be more costly and complex due to the specialized components and technology involved.
A furnace is generally considered old when it reaches 15 to 20 years of age. While well-maintained units can occasionally last up to 25 years, their efficiency drops significantly, and the risk of costly repairs and safety issues increases dramatically after the 15-year mark.
Federal tax credits for residential furnaces and HVAC systems expired at the end of 2025. If your furnace was installed and placed in service in 2026, it no longer qualifies for the Section 25C Energy Efficient Home Improvement Credit.
A standard residential furnace lasts 15 to 20 years. However, the exact lifespan varies based on the type of system and how well it is maintained.
The "best" furnace depends on your budget, climate, and how long you plan to stay in your home. Top-tier brands like Trane, Carrier, and Lennox excel in advanced technology and reliability, while Goodman offers superior upfront affordability and value.
Among them, the top four cities—Chongqing, Fuzhou, Hangzhou, and Nanchang—were dubbed the "New Four Furnaces" by many netizens, while Wuhan dropped out of the top four, ranking sixth. There is also a claim that Jinan ranked seventh on the national "furnace" city list.
Carrier and Rheem are both premier HVAC brands, but they cater to slightly different needs. Carrier leads the industry in premium, ultra-high efficiency and advanced communicating technology. Rheem is celebrated for offering a better balance of day-to-day value, long-term reliability, and easier-to-source replacement parts.
Many people choose furnaces much bigger, and therefore more expensive, than they actually need. A professional contractor can help you correctly size your furnace, and save you money. Adding an electronic setback thermostat to your new purchase will also help lower your overall costs.
Capacitors are used in nearly every heating system, from gas furnaces to electric furnaces to heat pumps. Even though other parts can fail, like the ignitor in a gas furnace or the compressor in a heat pump, the capacitor is by far the most common part to fail on a furnace because almost every system relies on one.
Goodman Furnaces
Goodman is one of the most affordable furnace brands on the market. While they don't always have the premium features of higher-end brands, Goodman furnaces come with excellent warranties and solid performance, making them a great choice for value-focused homeowners.