Swimming Pool Heating
Heating a swimming pool can consume a lot of energy
and add up to high heating bills. You can improve
your swimming pool's heating and energy efficiency
by doing the following:
Installing a high efficiency or solar pool heater
Swimming Pool Heaters
You can reduce swimming pool heating costs by
installing an energy-efficient pool heater. Here
you'll find more information about the following:
•Gas pool heaters
•Heat pump pool heaters
•Solar pool heaters.
Swimming Pool Covers
You can significantly reduce swimming pool heating
costs by using a pool cover. On the following pages,
see the tables showing the costs of heating pools
with and without pool covers in different U.S.
cities:
•Estimating Heat Pump Swimming Pool Heater Costs and
Savings
•Estimating Swimming Pool Gas Heating Costs and
Savings
Use of a pool cover also can help reduce the size of
a solar pool heating system, which can save money.
How They Work
Swimming pools lose energy in a variety of ways, but
evaporation is by far the largest source of energy
loss. Evaporating water requires tremendous amounts
of energy. It only takes 1 Btu (British thermal
unit) to raise 1 pound of water 1 degree, but each
pound of 80ºF water that evaporates takes a whopping
1,048 Btu of heat out of the pool.
The evaporation rate from an outdoor pool varies
depending on the pool's temperature, air temperature
and humidity, and the wind speed at the pool
surface. The higher the pool temperature and wind
speed and the lower the humidity, the greater the
evaporation rate. In windy areas, you can add a
windbreak—trees, shrubs, or a fence—to reduce
evaporation. The windbreak needs to be high enough
and close enough to the pool that it doesn't create
turbulence over the pool, which will increase
evaporation. You also don't want the windbreak to
shade the pool from the sun, which helps heat it.
Indoor pools aren't subjected to the environment,
but they still can lose a lot of energy from
evaporation. They even require room ventilation to
control indoor humidity caused by the large amount
of evaporation. The ventilated air also must be
conditioned, which adds to the energy costs.
Pool covers minimize evaporation from both outdoor
and indoor pools. Covering a pool when it is not in
use is the single most effective means of reducing
pool heating costs. Savings of 50%–70% are possible.
Pool covers on indoor pools not only can reduce
evaporation but also the need to ventilate indoor
air and replace it with unconditioned outdoor air.
You can also shut off exhaust fans when an indoor
pool is covered, which saves even more energy.
Types of Pool Covers
Technically, all you really need for a pool cover is
a large sheet of plastic. Plastic meets the
requirement of being a vapor barrier. But a large
sheet of plastic that you get from the lumber store
is probably not your best choice. It will be very
difficult to handle and store, it tears easily, and
sunlight will deteriorate it rapidly. You can use a
sheet of plastic, but it will be very inconvenient
and it will probably only last 1 to 2 seasons
maximum.
It's best to use a cover designed specifically for
swimming pools. They're made of special materials,
such as UV-stabilized polyethylene, polypropylene,
or vinyl. They can be transparent or opaque. Covers
can even be light or dark colored.
One of the lowest cost covers made specifically for
swimming pools is the bubble (or solar) cover.
Bubble covers are similar to bubble packing material
except they use a thicker grade of plastic and have
UV inhibitors.
Vinyl covers consist of a heavier material and have
a longer life expectancy than bubble covers.
Insulated vinyl covers are also available with a
thin layer of flexible insulation sandwiched between
two layers of vinyl.
Outdoor pools gain heat from the sun, absorbing
75%–85% of the solar energy striking the pool
surface. This is an important contribution to the
pool's heating needs. A pool cover will decrease the
solar gain contribution to some extent, depending on
what type you use. A transparent bubble cover may
reduce pool solar energy absorption by 5%–15 %. A
completely opaque cover will reduce it by 20%–40%.
You need to consider this when selecting a pool
cover.
You also need to decide whether you want a manual,
semi-automatic, or an automatic pool cover. You can
manually pull the cover on and off, fold it, and
place it somewhere out of the way. You can also
purchase a pool cover reel to help manually roll up
the pool cover. The reel, usually on wheels, can be
rolled out of the way.
Semi-automatic covers use a motor-driven reel
system. They use electrical power to roll and unroll
the cover, but usually require someone to pull on
the cover when unrolling, or guide the cover onto
the reel when rolling up the cover. Semi-automatic
covers can be built into the pool deck surrounding
the pool, or can use reels on carts.
Automatic covers have permanently mounted reels that
automatically cover and uncover the pool at the push
of a button. They're the most expensive option, but
they're also the most convenient.
Some pool covers fit into tracks along the sides of
the pool. This prevents anything or anybody from
getting into the pool. They even support the weight
of several people. If liability is a concern, these
are a good option to explore. They can be run
manually, semi-automatically, or automatically.
Safety covers are recommended for public pools, and
may be required by inspectors.
How to Use a Pool Cover
Pool covers should be used during your swimming
season. If you use your pool during the daytime,
take off the cover just before swimming and replace
the cover as soon as you're done using the pool.
If you use your pool only at night, the
effectiveness of a pool cover will depend on whether
the evaporation and other losses prevented by the
cover exceed the solar gain reduction caused by the
cover. The type of cover and the climate affects
this balance. In dry and/or windy conditions, the
evaporation rate of the pool increases. Therefore,
it is generally beneficial to have a transparent or
bubble cover on during daylight hours. In warm,
humid conditions the evaporation rate decreases. In
this case, it may be more beneficial to leave the
cover off during the daytime.
Other Pool Cover Benefits
Besides offering energy savings, pool covers also do
the following:
•Conserve water by reducing the amount of make-up
water needed by 30%–50%
•Reduce the pool's chemical consumption by 35%–60%
•Reduce cleaning time by keeping dirt and other
debris out of the pool.
•Swimming Pool Pump Efficiency
•Swimming Pool Water Temperature Efficiency.
Managing the water temperature
Managing Swimming Pool Water Temperature for Energy
Efficiency
The water temperature you desire for your swimming
pool not only affects the size of the pool's heater,
but also your heating costs if use a gas or heat
pump pool heater.
Pool water temperatures typically range from 78ºF to
82ºF. The American Red Cross recommends a
temperature of 78ºF for competitive swimming. This
coincides with good fuel savings. However, this may
be too cool for young children and the elderly, who
may require a temperature of 80ºF or higher.
The energy consumption for each degree rise in
temperature will cost 10%–30% more in energy costs,
depending on your location. In warmer climates, this
percentage is higher because of the relatively low
cost of heating a pool at 78ºF. On the following
pages, see the tables showing the costs of heating
pools at different temperatures in different U.S.
cities:
•Estimating Heat Pump Swimming Pool Heater Costs and
Savings
•Estimating Swimming Pool Gas Heating Costs and
Savings
Also, turn the temperature down or turn off the
heater whenever the pool won't be used for several
days. This will save energy and money. It's a myth
that it takes more energy to heat a pool back up to
a desired temperature than you save by lowering the
temperature or turning off the heater.
Installing a smaller, energy-efficient pump
and/or operating it less.
Installing and Operating a Swimming Pool Pump for
Energy Efficiency
You can save energy and maintain a comfortable
swimming pool temperature by using a smaller, higher
efficiency pump and by operating it less.
In a study of 120 pools by the Center for Energy
Conservation at Florida Atlantic University, some
pool owners saved as much as 75% of their original
pumping bill when they used these energy
conservation measures (see table below).
