Description
Heat
pump water heaters - also known as hybrid water heaters - are generally
considered to be the most energy efficient water heaters on the market. (Note:
Because they run on electricity, you may also hear people refer to them as
electric heat pump water heaters).
As a
result, they have lower operating costs and a much lower carbon footprint. Many
homeowners can save between $200 and $600 a year by switching to a hybrid water
heater. The only energy-saving projects that will save you more money are
replacing your heating and cooling system with a heat pump HVAC system, and
improving your home insulation.
They
cost more to install than electric or tankless water heaters. But with the cost
savings so high, these systems usually pay for themselves quickly.
How does
a heat pump water heater work?
Heat
pump water heaters -- also known as hybrid water heaters -- draw heat from the
surrounding air to heat the water, rather than relying on electricity or gas.
In other words, they move energy rather than generate it. In this way, they use
essentially the same technology as heat pumps for space heating and cooling.
As the
DOE researchers put it, "The heat pump works like a refrigerator. The
refrigerator absorbs heat from the inside of the box and dumps it into the
surrounding room, while the stand-alone air source heat pump water heater
absorbs heat from the surrounding air. And dump it into the tank at a higher
temperature to heat the water.”
Most
heat pump water heaters these days also include a back-up resistance heater in
case the ambient air temperature isn't hot enough to use. That's why they call
them hybrid heat pumps.
Because
they use ambient air, heat pump water heaters need to be placed in an area of
your home that stays within the 40º–90ºF (4.4º–32.2ºC) range year-round. They
also need at least 1,000 cubic feet (28.3 cubic meters) of air space around the
water heater to work.
Pros and
Cons
Advantage
1.
Energy efficiency
Apart
from solar water heaters, heat pumps are the most energy efficient. Most of
them have an energy factor of at least 2 (compared to 0.6-0.98 for traditional
tanks). This means you will spend less on your electricity bill each year than
with a traditional electric water heater.
2.
Environmentally friendly
Since
their energy efficient heat pump water heaters are also the most
environmentally friendly. Their carbon footprint can be 2-4 times lower than
conventional tanks. That's why environmental groups like NRDC and RMI love
them.
3.
Rebates and Incentives
The
federal government will give you a $300 tax credit for the purchase of a heat
pump. Some states like Maine will give you an instant rebate of $750. Many of
the largest utilities like Xcel will give you $500 in rebates. Visit the
National Renewable Energy and Efficiency Incentives Database to find out which
rebates and incentives you qualify for.
Shortcoming
1. More
expensive upfront costs
If you
live in a place that doesn't offer a heat pump water heater bonus, it may cost
more upfront. This is because units are generally more expensive than electric
and tankless water heaters and are more complicated to install (which means
more plumber hours).
2. Some
background noise
Some
homeowners have complained of a slight hum in the background when the hybrid
heat pump is running. However, if you install it in the correct location, this
shouldn't be a problem.
3.
Prepaid
The
upfront cost of a heat pump depends on a number of factors, including the
equipment you purchase, how long it will take to install, and how much
incentive you are eligible for.
4. Unit
cost
Heat
pump (hybrid) water heaters with 50-gallon tanks from the highest-end
manufacturers cost anywhere from $1,200 to $2,500 for an 80-gallon tank. Tank
size and product quality have the greatest impact on unit cost.
5.
Installation labor
-
Installation of a Hybrid Heat Pump Water Heater (HPWH) takes about 6 hours and
costs between $600 and $800.
6.
Electrician labor
If
you're replacing a traditional electric water tank, you've equipped your HPWH
with power. But if you're replacing a gas heater, you may need to bring an
electrician to run the 220-volt circuit. This should cost $132-272.
7.
Supplies and Tools
Your
plumber will need some supplies to set up your HPWH. This should cost between
$172 and $218.
8.
Processing costs
Some
plumbers charge $25-75 to remove old water heaters. But many of them do it for
free.
So, as
you can see, the upfront cost of installing a hybrid water heater is higher
than installing small energy efficiency projects like LED lighting. But it's
still far cheaper than replacing your space heating and cooling (HVAC) with a
heat pump.
Annual
operating cost
The
operating cost or estimated annual cost of running a heat pump water heater
will depend on your heater efficiency rating, the cost of energy where you
live, and the amount of hot water you use.
The
following are the factors that have the greatest impact on operating costs:
1.
Energy factor
This is
a measure of how much electricity your HPWH needs to heat your water. Most heat
pumps have an energy factor of 2, which is about 2-3 times that of a
traditional water tank.
2.
Energy consumption/use
This is
how much energy your heat pump will use each month or year. According to the
Department of Energy, the average heat pump uses 2,195 kWh of electricity per
year (kWh/yr). However, the larger the tank, the more energy you should use.
3.
Energy costs
This is
the electricity bill where you live. Electricity costs are measured in cents
per kilowatt-hour ($/kWh). If you live in the South where electricity is cheap,
you will pay a lot less than if you live in California or Hawaii, where
electricity is more expensive. This EIA data shows the average electricity
price in each state. But to get the exact number, you'll need to look at your
utility bill.
The
average annual running cost for a water heater is about $225, compared to
$400-$800 for many traditional tank water heaters. According to Energy Star,
for a family of four, the average cost of running an HPWH is $300 per year,
compared with $600 for an electric storage water heater.
Size
Guide
To
figure out what size hybrid water heater you need, you should look at the
"First Hour Rating" for each model you evaluate. The first hour
rating tells you how much hot water you can use in any given hour before the
tank has to refill and reheat more incoming water.
Then you
need to estimate the maximum amount of hot water you and your family will use
at any given time. The way to do this is to look at the flow for all end uses
(shower, faucet, dishwasher, etc.) and add up the flow you will use in the same
hour.
The
average shower uses 2 gallons per minute (low-flow shower heads use less). If
two people live in your home and take a 10-minute shower back to back, that
will require 40 gallons of hot water.
But
let's say one of you needs to shave after the shower. The average flow rate of
the tank is 0.5 gallons per minute. If it takes 2 minutes, another 1 gallon of
capacity is required.
Now
suppose you want to run the dishwasher after the shower. Dishwashers use an
average of 6 gallons (4 gallons for energy efficient models).
If you
add all of that up, you get 40 + 1 + 6, or 46 gallons. That means you probably
want a 50-gallon tank.
But
remember, the bigger the tank, the higher the cost. So if you want to save
money, you can choose to run the dishwasher at night and shower in the morning.
Or you and your partner can take 3 minutes off the shower and only need a
40-gallon tank.
Install
Probably
one of the biggest factors driving your decision is the installation process
(or possibility). We've written a complete guide here that covers the
installation and cost of tankless water heaters. So we won't go too deep here.
But heat
pump water heaters can be installed just like regular electric water heaters.
They're basically just more efficient versions of the standard water heaters
you've probably seen in your life. Tankless water heaters, on the other hand,
are a little different. Usually people install them for specific use cases. For
example, in a house I once rented, we had one because there wasn't a closet big
enough for a large water tank. So our landlord put a tankless water heater in
the small attic. Why? Because it's the only thing that fits. Or to draw from
another personal experience, a friend of mine installed one near the guest
bathroom because it didn't require much hot water. It sticks easily in the
bathroom closet and doesn't take up valuable closet space.
So, as a
rule of thumb, our advice is: if you can, install a heat pump water heater.
You'll save money, energy, and your investment will outweigh the return. If you
can't install it or can't afford it, use a tankless water heater.
But, for the sake of my future, your children's future, and the future of this beautiful planet, please do not install natural gas or oil water heaters. If you do, you're basically guaranteed to emit tens of tons of carbon and burn dangerous gases in your home for decades to come.
