Heat pumps are not new to the market but the price of fossil fuels has made them a lot more attractive. Also, as technology has improved, their operating cost has dropped dramatically leading to higher levels of efficiency. What is efficiency? How do they work? When should you invest in one instead of a gas or solar system? What does it cost to run? These and some other questions are considered here so read on.
The efficiency which is talked about in relation to heat pumps is also called Coefficient Of Performance or COP. This gives a relationship between the amount of energy used to the amount of energy produced. To compare apples with apples, a common electric immersion heater (such as in a kettle) is around 90% efficient so would have a COP close to 1 but heat pumps can be rated with a COP of 5 which means an efficiency of 500%. This is because heat pump does not actually create heat (like an immersion heater does) they just move it from one place to another.
This is something the prospective purchaser must be aware of because heat pumps have a drawback. Electric heat pumps take heat from the air and transfer it to the pool water so as the air temperature drops so does their efficiency. In fact, once the air temperature hits around the 45 degrees F mark, they stop working and can even freeze up!
When comparing different brands for efficiency it is very important to make sure the COP is calculated under the same conditions for each pump.
How Does A Heat Pump Work?
If you have a refrigerator or a non-evaporative air conditioner you already have a heat pump. In fact a car radiator is a heat pump. In basic terms, you are using a liquid or gas to pick up heat at one point then pumping it to a radiator (or heat exchanger) and releasing it. A fridge is moving heat from inside the box and pumping it to a radiator outside the box where it goes into the air – that is why there is heat around the outside of your fridge.
So a swimming pool heat pump will take heat from the surrounding air and move it through refrigerant gas and a compressor to a heat exchanger releasing the heat into the pool water flowing around it. The cooled gas travels on through piping back to where it started and picks up more heat and so on. This is also called a "closed loop" because the gas keeps on traveling around it.
Should I Purchase A Heat Pump?
This is a more difficult question to answer. There are reasons for using heat pumps and there are reasons for opting for a gas or solar heater. The main question you need to ask is will you want to heat your pool water when the air temperature drops below the 45 to 50 degrees F mark? If so then forget it – your best bet is probably a gas heater. Will a solar pool heater extend your swimming season enough? If you have the space, a solar system may be best even though it could cost more to purchase initially.
A heat pump will heat your pool water on demand so you do not have to worry about overcast weather as you do with a solar system. Usually you would set the required water temperature and the heat pump will run as needed to keep that temperature. They can be used to heat a pool from cold if you only want to use the pool occasionally but gas heaters are better at this.
They are easy to install requiring some straightforward PVC plumbing and an electrical connection (use a contractor for that) and do not take up a lot of space.
There are above ground electric pool heaters available as well as in ground models.
What Is The Cost Of A Heat Pump?
The initial purchase cost will be somewhere between $ 2,000 and $ 5,000 depending heavily on the heating capacity (measured in BTUs). A larger heating capacity will result in faster heat-from-cold times but will add more to your power bill. The running cost is about half that of a gas pool heater. The running cost can be reduced by about 60 to 80% if you use a pool cover. Pool covers not only help keep debris out but keep water in by reducing evaporation. Evaporation accounts for around 80% of pool heat loss so installing a pool cover should be very high on your to-do list! Depending on where you live you could expect your power bill to increase by about $ 700 to $ 2,000 per year without a pool cover or $ 100 to $ 400 if you use a cover.
Heat pumps do have quite a few moving and electrical parts so it is a good idea to have them serviced yearly to get the best efficiency and lifespan out of them. Your user manual will normally have a recommended maintenance schedule. With proper maintenance they should last 10 years or more. Proper balance of your pool chemicals is vital other damage could result and efficiency will drop.
In conclusion, do a little homework before you commit to one type of pool heater over another. They can all sound great on paper but a little thought about your particular needs and situation could help you make the right decision. Heat pumps have some great advantages to consider and some disadvantages too.