Buying a Heat Pump
A
heat pump is essentially an air conditioner that can both heat and cool
a house. (For more information on how a heat pump accomplishes this bit
of wizardry, please see our article on how heat pumps work. A simple
explanation is that a heat pump can extract heat found in the air (or
ground) outside your house and transfer that heat into your house
instead. Under the right conditions it can do this substantially more
cheaply than a gas or oil furnace.
Consider the following questions when buying a heat pump:
- Is a heat pump the best choice -- or would you be better off buying a furnace and
a central air conditioner? - What size heat pump should you buy?
- What is heat pump efficiency, and how efficient should your heat pump be?
- Which brand of heat pump is best?
- Who should install your heat pump?
Is a Heat Pump the Best Choice?
Since a heat pump can both heat and cool a house, wouldn't you always
rather buy a heat pump than a central air conditioner? And wouldn't you
rather have a single piece of equipment to purchase, install and
maintain than both a central air conditioner and a furnace? While the
answer may be this simple, you should consider several factors.
The
seasonal weather in your region is probably the most important factor
in this decision. If the temperature rarely dips below 40 degrees
Fahrenheit, you can probably heat your home more affordably with a heat
pump than a furnace. However, if the temperature is often colder, you
should consider having a backup heat source. Many people choose a gas
or oil furnace to serve this purpose -- both for reasons of cost and
because a furnace can more easily maintain warm temperatures when the
difference between the temperature outside and inside increases.
Second, heat pumps are generally more expensive than a central air conditioner of the same efficiency and capacity.
A
third criterion to consider is longevity. Since a central air
conditioner is typically only used during the summer months, and a heat
pump is used during both summer AND winter, the lifespan of a heat pump
is typically shorter than that of a central air conditioner.
Maintenance costs are typically higher as well, since the compressor,
controls and other components will run more months out of the year.
Finally, natural gas and oil have historically been more affordable
than electricity. However, as petroleum costs have skyrocketed in the
past years, this may not be true in your area.
What size heat pump should you buy?
Choosing a heat pump that outputs the correct amount of warm and cold
air ensures comfort, low maintenance, and efficient operation. Heat
pumps should be sized to run continuously to maximize efficiency. A
heat pump that is too large for your house cycles on and off too often,
which increases the wear on the equipment and decreases its efficiency.
Too small, and the unit may not be able to keep you comfortable during
both summer and winter.
Unfortunately,
there is no shortcut to an accurate measurement -- you need to get an
HVAC contractor to calculate your house's heating load. The standard
measure of a heating load is a Manual J calculation, and it takes into
account your house's insulation, size, amount of shade, and many other
factors.
Heat Pump Efficiency: SEER vs. HSPF
The heating and cooling functions of a heat pump each have their own
measure of efficiency. A heat pump's cooling efficiency is measured by
its "Seasonal Energy Efficiency Rating", or SEER. Its heating
efficiency is measured by its "Heating Seasonal Performance Factor" or
HSPF.
In warm climates where you'll want to generate cool air often and hot
air rarely, you'll want to choose a heat pump with a high SEER. In
cooler climates, you'll want to make sure that your heat pump has a
high HSPF.
Highly
efficient heat pumps typically cost more than less efficient models.
You may want to consider how many months it will take to pay off this
increased cost through savings in your energy bill. If you are planning
to leave your current house within a few years, you might prefer to
install a lower efficiency heat pump, as you are unlikely to recoup the
extra cost. (Of course, money is not the only factor to consider -- you
may be willing to pay more to reduce your house's impact on the
environment.)
Who should install your Heat Pump?
One of the most important choices you will make in buying a heat pump
is which contractor to hire. A good contractor will correctly size your
heat pump, help you calculate the payback period of high and
low-efficiency equipment, and ensure that the equipment is installed
properly. In addition, they will respond promptly when you have an HVAC
crisis, provide ongoing maintenance, and act as a go-between with the
manufacturer to replace failed parts under warranty. Much like choosing
a lawyer or an accountant, you should approach the choice of an HVAC
contractor carefully.
Approach your selection of an HVAC contractor the same way you would
hire an employee -- interview several, get references, and decide
slowly. Probably the best way to start is to call friends that live in
your town, and ask them who they would recommend. Small businesses
(such as the typical HVAC company) live and die by word-of-mouth
referral -- if a contractor knows that one of their current clients
referred them to you, they will work harder to make you happy.
Make
sure to ask your contractor to show you a license and proof of
insurance. Ask if they will perform a load calculation to determine how
large of a heat pump to install. If they suggest that they have a
shortcut for determining the correct heat pump size, keep looking! In
addition, check with the Better Business Bureau to see if anyone has
filed a complaint about their company. Ask for references from three
previous customers -- and then call to follow-up with those references.
Make sure that there's a good fit between personalities -- you want to
be sure that you feel comfortable asking questions. While price is
usually an important consideration, make sure that the low-cost
contractor you hire has an excellent reputation!
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