The viable solution in any situation
Heat pumps can work in temperatures as low as 5 C (41 F); the hotter it is outside, the better, since heat pumps transfer ambient air heat energy into the pool water.
First, it is important to get a unit that is the right size for the pool. A general rule of thumb is to install a minimum one to two Btus of capacity for every litre of water in the pool. When possible, it is recommended to select a unit that can deliver beyond the homeowner’s minimum requirements.
Heat pumps with higher capacities offer many advantages: they operate less, they get the pool to a desirable temperature faster, and they will be able to maintain the target temperature longer into the season.
Time to payback
When looking at the heater costs table (Figure 1), it is easy to see the huge difference in yearly operating costs depending on the type of unit that is installed. There are also differences in local energy costs for electricity, propane, and natural gas, as well as variances in personal preferences for desired temperatures and, of course, pool shapes and sizes vary, too.
However, all things considered, it is only a matter of time before the lower monthly energy bills cover the increased upfront cost of a heat pump. In most cases, this takes between two and five years.
Figure 1: Pool heater cost comparison
|Installation||Heat Pump||Natural Gas Heater||Propane Heater|
|Output||120,000 Btu/hour||232,000 Btu/hour||198,000 Btu/hour|
|Efficiency||Heat pump COP6||82 per cent||80 per cent|
|Costs per:||kW $0.15||Million Btu $13.40||Litre of propane $0.60|
|Initial cost to heat up pool||$24.22||$54.34||$100.88|
|Cost per day to keep water at desired temperature||$4.54||$10.19||$18.92|
|Runtime per day (hours)||5||3||3|
|Cost for season||$569||$1,280||$2,371|
|Cost difference per season||—||$711||$1,802|
*These are approximate figures based on calculations for a 75,000-L (19,813-gal) pool, heating in average seasonal temperatures in Toronto between June to August.
Making an environmentally conscious choice does not solely rely on pool owners. For instance, heat pumps do not burn propane, natural gas, or oil, keeping greenhouse gases out of the air, which is a preference supported by many energy suppliers. Another reason why a pool owner may choose an electric-powered heat pump over a gas-fired unit is 90 per cent of the electricity in Ontario is generated through non-carbon sources (60 per cent nuclear, 24 per cent hydro, and six per cent wind). An electric heat pump that turns every kilowatt of power it uses into seven kilowatts of heat is, therefore, extremely efficient and one of the most environmentally conscious choices a pool owner can make.
The most cost-effective heat pumps can help to optimize the entire pool system when combined with other high-efficiency equipment, such as a variable-speed pump (VSP). The combination of these systems makes sense because heat pumps operate more efficiently when there is a higher rate of flow through the system; however, operating the pool in this manner 24-7 is counterproductive, as it can also waste energy. Therefore, to improve efficiency, a VSP allows the flow rate to be increased when the system is actively heating and, when the desired temperature is reached, the flow rate is reduced, thus increasing energy savings.
By decreasing the amount of time the pump is running at high flow, the system emits less overall ambient noise, which is another advantage of combining these technologies. This is ideal for neighbourhoods where homes are located close together, or where municipal noise bylaws are stricter. In general, noise restriction is an increasingly important issue throughout North America and heat pump manufacturers invest significant resources in research and development to address it. Consequently, the best units boast an operating noise level of only 50 to 55 decibels.
That said, it should come as no surprise to the homeowner that leading heat pump manufacturers and installers will recommend combining a VSP with any new unit to maximize efficiency. However, something to look out for when pricing these two complementary components is an assurance they can work together properly. Some manufacturers may even offer unique, simple operating modes that enable the pool heater to communicate with a VSP.