Furnace Buyer’s Guide

The Complete Furnace Buyer’s Guide

Buying a new furnace can be a daunting task, especially if you find yourself in a situation where your current furnace is broken beyond repair and you need a new one quickly. Even if you’re just replacing your old furnace with a new, more efficient model to offset energy prices, the seemingly endless options can be overwhelming. Money aside, today’s furnaces pollute less and boost comfort with ease by producing heat more steadily than older ones. At HVAC Philly, we have over 20 years of experience in all areas of heating and air conditioning, so today, we’re putting our expertise to use to give back to you and make your furnace buying experience as easy as possible. Read on for our expert buyer’s guide. Since gas is the most common heating fuel, this guide focuses on gas furnaces.

How do most people go about buying a furnace? Usually, they call contractors and ask for estimates. It’s hard to beat the expertise of a seasoned HVAC expert on your own, but learning about the different aspects of furnaces will ensure you are getting the best deal for yourself.

Size Matters

When it comes to choosing a furnace, you should know that size matters–a lot.

The specifications of the furnace you buy should fit your needs and home size. A furnace that’s too small won’t keep your house comfortable when you need it to most. Interestingly, furnaces in most homes are larger than necessary to avoid underperformance during extreme weather. While getting a furnace that’s larger than necessary will guarantee your comfort no matter the weather conditions, you are going to have to pay a higher initial cost for the peace of mind.

It’s also important to note that a furnace that’s too large will cycle on and off more frequently. Frequent cycling puts more wear on the furnace’s components, wastes energy, and can cause your home temperature to vary uncomfortably. Don’t forget that a larger replacement furnace might require larger ducts. Without the right size ducts, airflow can be noisy.

To be sure of correct sizing and a proper installation, choose a reputable contractor who will take the time to calculate your heating needs according to industry standards. Such calculations take into account the climate as well as the size, design, and construction of your house. If you live in Philadelphia, Montgomery, or Bucks County, give us a call at HVAC Philly for a free estimate!

Once the furnace is installed, it’s important to perform regular maintenance according to the manufacturer’s recommendations. (Read here for tips on furnace maintenance)

Is it Efficient?

Why is efficiency important? It’s important because it saves you money and generates fewer emissions, which in turn helps the environment! How efficiently a furnace converts gas into heating energy is reflected in its annual fuel-utilization-efficiency (AFUE) rating. The higher the percentage, the more efficient the furnace.

Over the years, furnaces have of course become much more energy-efficient. A gas furnace made in the early 1970s typically has an AFUE of about 65 percent. The lowest efficiency allowed by law for new gas furnaces is 78 percent, and some new models achieve 97 percent–near-total efficiency.

The price of a furnace generally rises in step with its fuel efficiency. A furnace with a 90% AFUE might cost $1,000 more than a similar size unit with an 80% AFUE, but you can often recoup that additional cost through lower fuel bills over the life of the furnace. AFUE is especially important in regions such as the Northeast and Midwest, where winters can be harsh. How quickly you recover your investment depends on more than just AFUE. Variation in electricity use needed to run the furnace, local climate, home insulation, and your local gas and electricity rates also affect payback times.


As you start looking for a furnace, insist that your contractor select models in a range of efficiencies and calculate the annual estimated operating cost of each model you’re considering, rather than simply estimating it. The contractor can complete these calculations by entering information on each unit’s electrical consumption and AFUE, local utility rates, and characteristics of your home into a computer program designed to easily calculate estimates. Make sure that the quotes also include the cost of any changes to venting required by any appliances in the home.

Despite the improved efficiency of most new furnaces, it’s generally more cost-effective to repair a furnace than to replace it. However, if a key component such as the heat exchanger or control module fails, you’re probably better off replacing the furnace, especially if the unit is more than about 15 years old (furnaces typically last an average of 15 to 18 years). If you have to replace your furnace, you’ll be glad to hear that today’s more-efficient gas furnaces can save you up to $40 for every $100 you spend on fuel compared to older models. More efficient furnaces are also, on average, less likely to need repairs, which is why reliability is so important.

Ask your contractor if the model you’re considering has been newly introduced, say, two years ago or less—and is thus relatively untested. If it’s an older model, ask if the contractor has noticed any reliability problems with it. According to our numbers, 77% of furnaces that break down need significant work. A majority of that 77% broke down completely, and nearly a third produced no heat for more than a day. 40% of the broken furnaces incurred a repair cost of $150 or more.

Types of Furnaces

You have several choices in energy sources to heat your home and water. Know that prices will vary widely according to the type of furnace and the installation, and you may have to do your research to find out what’s best for you.


Gas is currently the most common heating fuel. Most new central-heating systems use gas, which is the focus of this report.  Generally, gas furnaces are recommended, but there are situations where you could benefit from having a different type of furnace.


Oil furnace models still retain a niche in older homes, mostly in the Northeast, but heating costs are usually much higher than those of gas furnaces.

Heat pumps

Heat pump furnaces that wring heat from outdoor air (and reverse the process in summer to act as an air conditioner) are inexpensive to install as an alternative to a cooling-only air-conditioning system. This feature makes them the preferred way to heat in the South and Southwest where winters are typically short and mild. Heat pumps that wring heat from the ground are much more expensive to install, but they are suitable for cold climates because they can maintain their operating efficiency.


Alternate inexpensive electric-heat options include strip heaters, which are installed in the ductwork of central air conditioning and on permanently installed baseboard units in each room. Before you consider any type of electric central heating system in colder regions, keep in mind that electricity rates are much higher than those for natural gas and are likely to remain that way for the foreseeable future. You can find rate information for various fuels from local utilities and suppliers.

Furnace Features

Each brand of furnace offers a similar array of key features, depending on price. The furnace features that are most often highlighted are generally the ones included with higher-efficiency models, but some manufacturers also offer them on premium versions of low-efficiency furnaces.

Variable-Speed Blowers

These can deliver air at a slower speed (while often making less noise) when less heat is needed. This speed variation produces fewer drafts and fewer uncomfortable temperature swings.

Variable Heat Output

Available on some furnaces that have a variable-speed blower, this feature can increase efficiency and comfort by automatically varying the amount of heat the furnace delivers. The furnace can thus deliver heat more continuously than one with a fixed heat output could. Again, this reduces uncomfortable temperature swings.

Air Filtration System

Fitting a furnace with an electrostatic filter, which uses an electrical charge to help trap particles, or a high-efficiency particulate-arresting (HEPA) filter can reduce the amount of dust blown through the heating system. These filtration systems may help people with asthma or other chronic lung diseases, but there’s little evidence that other people need such filtration.

Dual Heat Exchanger

Heat exchangers are the components that draw heat from the burned gas. To draw more heat from the air they burn, energy-efficient furnaces supplement the primary exchanger with an additional exchanger. Because the exhaust gases in that second exchanger might yield a corrosive acidic condensate, the second exchanger is made of stainless steel, lined with plastic, or otherwise protected.

Ignition system

Fewer and fewer furnaces have a pilot light–a flame that burns continuously, awaiting the next command to ignite the burners. I don’t know about you, but I’ve personally never been too comfortable with the idea of a constantly burning small fire in my house. Furnaces with intermittent, direct spark, or hot-surface ignition do away with the constant pilot light in various ways. These systems increase efficiency which is usually reflected in a furnace’s higher AFUE rating.

Regardless of what type of heating system you have, if you live in Philadelphia, Bucks or Montgomery County, our team at HVAC Philly will help you find an affordable solution! Contact us today at 215-725-6111 to learn about all of our options and solutions for your heater repair and installation service in the Philadelphia area.


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