Don't get burned by a bad furnace
New furnaces are more complex than ever
with lots of new features, higher efficiencies
and higher costs. Knowing what to ask an
HVAC contractor is key to buying the right furnace
for your home and getting a quality
We asked experienced TFH Field Editors—HVAC pros who do this for a living as well as
fellow DIYers who have recently bought a furnace—for their top tips, warnings, lessons
learned and best advice about buying a new
Top tips from an HVAC pro
1 of 1
Dave Jones is a 35-year licensed professional engineer and a TFH Field
Editor. He is the Engineering & Design Manager at Temperature Systems
Inc. in Madison, WI, and has been involved in the design and construction
of hundreds of HVAC projects across the United States, ranging from lake
cabins to large research facilities.
- Don't go with the lowest bidder
“Service calls are twice as likely to be related to poor installation as to defective equipment. The
guy with the lowest bid often makes the biggest mistakes.”
- Contractor markup makes a difference
“The heating contractor actually pays about $300 to $500 more for a 95 percent furnace than he
does for a 90 percent furnace. So, if that added cost is passed through with little markup, you
might be able to cost-justify it. If the contractor marks up the price a whole bunch, then you have
no chance of making a payback in your lifetime.”
- Have a pro install a new thermostat
“Furnaces and thermostats, just like cars, have gotten increasingly computerized, and they can
require some pretty serious know-how to get them to work right.”
- High vs. very high efficiencies
“Higher efficiency means higher complexity, and I like to keep the machinery as simple as possible.
The more complex it is, the more expensive it is, and the more it will cost to fix when it
breaks. Generally, your very best value is to get a 92 percent efficiency furnace with one of the
new ECM fan motors.”
- Get a proposal, not a bid
“Go with someone who provides a detailed written proposal that outlines exactly what he will
and won't do. He should list the manufacturer and model number of the proposed equipment as
well as the cost of any plumbing, venting changes or electrical work required.”
- Buy a reputable brand
“Stick with the major brands or one of their subsidiaries. If you don't recognize the brand, don't
trust what the contractor says about it. Do your own checking online before you buy.”
- You may need a smaller furnace
“Older furnaces were usually oversized so that the house was always warm enough. But new
higher efficiency furnaces can have a lower Btu rating and still put out the same amount of heat.
For example, a new 94 percent efficient furnace that is rated at 80,000 Btu puts out as much
heat as an old 75 percent efficient 100,000 Btu furnace.”
New Law May Affect Your Choice
Beginning in May 2013, a new U.S. Department of Energy rule requires
newly installed residential gas furnaces in 30 northern states to be
rated at least 90 percent AFUE (annual fuel utilization efficiency). That
means your new furnace will vent directly through the wall instead of
up your chimney or stack. Check with a local HVAC professional for
more information or visit appliance-standards.org/product/furnaces.
Assess Your Entire HVAC SystemWhen you're shopping for a furnace, get
your ducts checked at the same time.
There's no sense in getting a new furnace
if you’ll let the hot/cold out through leaks
or poor insulation in your ductwork.
Mid- or high-efficiency furnace?
1 of 1
Which efficiency furnace is best?
Factor in local energy costs, rebates and tax credits and contractor markups when you compare furnaces.
Cost: $1,500 to $2,500 installed (no A/C) AFUE: 80 to 89 percent.
Savings: 15 to 20 percent of current heating costs (when replacing a 65
percent efficient unit).
Venting: Into a masonry or metal chimney (existing chimney might
Cost: $3,000 to $5,000 installed (no A/C) AFUE: 90 to 97 percent.
Savings: 25 to 30 percent of current heating costs (when replacing a 65
percent efficient unit).
Venting: Directly through a wall to the outside through plastic PVC pipe.
Known as “condensing units” because they recover extra heat from combustion
gases by extracting water from them.
Highest efficiencies make sense when...
- You live in a cold climate (may be required by law—see above).
- You will be staying in your house for 10 years or more.
- Local energy costs are high.
- You're replacing an inefficient heating system.
- The contractor markup is low (see “Top Tips from an HVAC Pro” above).
- You can take advantage of local, state and utility rebates and incentives.
Federal tax credits on high-efficiency furnaces were not renewed for
2012. But state, local and utility rebates may still be available in many
areas. Visit dsireusa.org for more information.
- The payback calculation is reasonable. Visit yourmoneypage.com/
energy/furnace1.php to run a payback calculation.
Highest efficiencies have higher repair bills
1 of 1
Diminishing returns?I'm an HVAC repairman.
Most furnace installers
prefer that you buy the
most efficient furnace
and claim it will save
you money. What they
don't tell you is that the
parts to repair it are
about three times as
expensive and in the
long run you're not
saving anything. You can
buy a furnace rated at
95 percent and still stay
away from the high
repair bills of a 97 or 98
Single-stage or two-stage blower?
A traditional single-stage furnace runs the burner at full blast and shuts off until
heat is called for. It costs $500 less than a two-stage furnace, but the trade-off
is lower energy efficiency, hot and cold spots, and inconsistent temperatures.
A two-stage furnace has a high and a low burner setting. It normally runs
on low unless full blast is needed. It costs $500 more than a single-stage
unit, but it delivers consistent heat, which means fewer drafts and temperature
swings, and is quiet and energy efficient.
Two-speed or a variable-speed blower?
A standard two-speed blower (aka “multi” speed) with a PSC motor
has one blower speed for heating and one for cooling. It's $600 cheaper than a
variable-speed blower and is less complex, which means lower future repair
costs. But it's noisier than a variable-speed blower and uses more electricity.
A variable-speed blower uses an ECM motor, which runs on DC
power and continually adjusts its speed to your home's needs. It uses a fraction
of the electricity of most standard motors and is quiet and comfortable. It
costs $600 more than a standard blower and is a more complex system,
which potentially means more expensive repairs.
Consider buying through a home center
1 of 1
Steve's next project is a display case for the
large wood sailing ship models he builds.
We got quotes from a few local contractors
but went with a home center instead. The
home center hired a reputable local company
but backed the work, and even gave us a small
discount for opening a credit card and charging
the work on it.
Use an experienced pro
1 of 1
Bruce just finished remodeling
his den from the studs up.
Stick with reputable furnace contractors who have been
in business for a long time. Chances are they're still in
business because they do quality work, and they'll still
be around if you have problems down the line.
“Our HVAC company went out of business
two years after they installed our
unit. If we have a problem with it, there
could be a big headache down the line.”
Incentives can slash the price
1 of 1
Tom just wrapped up a
half-bath remodel (taking
the room down to the
studs and the subfloor
My gas company gave me a
$100 rebate, the manufacturer
gave me a $500 rebate
and the city gave me a five-year
interest-free loan to
make the upgrade. I ended up
saving a bundle.
Don't assume the contractor knows everything
1 of 1
Tom has taken on HVAC as a hobby and has
reduced his utility costs by 25 to 30 percent by
sealing ductwork and replacing his own furnace,
thermostat and other HVAC equipment.
Most contractors I've talked to don't recommend variable-speed
blowers because they don't really understand them. I dug into
manufacturers' documentation and a few contractors' message
boards on the Internet and read until I understood
them. I guess that's what DIY is all about.
Put details in writing
1 of 1
Jeff's recent projects
flooring and cabinets in his children's
home schooling classroom.
Confirm that your
contractor will remove
your old furnace
Know the true cost of the furnace
1 of 1
David is currently
building a dock for
I got quotes from $2,800 (furnace
and ductwork) to $12,000. Do your
own research on the Internet and
find out how much you can purchase
the unit for online so you can
separate the unit from the labor.