How a pool heat pump actually works
A pool heat pump is a refrigeration circuit run backwards. A fan pulls outdoor air across an evaporator coil, the refrigerant absorbs heat from that air and is compressed, and a titanium coaxial heat exchanger transfers the heat into the pool water before the refrigerant expands and starts again.
Titanium is used for the water side because pool water carries chlorine and a variable pH, and copper pits in it. The refrigerant is R-410A on most installed units and R-32 on newer ones.
The efficiency figure is the coefficient of performance, and it is the reason the technology is worth considering. A pool heat pump returns roughly 4 to 6 units of heat per unit of electricity at mild rating conditions, against a gas heater's 0.82 to 0.84 units of heat per unit of gas energy. The heat pump is not creating that heat, it is moving it, which is why the ratio can exceed one.
The limit nobody puts in the quote
Output falls as air temperature falls, and it falls steeply.
A pool heat pump works well when outdoor air is warm and loses most of its usefulness below about 10 °C. In Guelph that means it performs through July and August, works acceptably in June and early September, and is close to useless in the third week of May or the first week of October, which are exactly the weeks people most want the pool warm.
Below roughly 7 °C many units will not run at all, and some will ice their evaporator coil trying. A unit that ices on a mild day is usually short of refrigerant or short of airflow rather than defective.
We say this before quoting, not after. A heat pump sold to someone who wants a heated pool in the third week of May is a complaint waiting to happen, and it is the single most common reason we are called out to a heat pump that is "not working" when it is in fact working as designed.
Electrical capacity, the heat pump equivalent of the gas meter
A gas heater is limited by the gas service. A heat pump is limited by the panel.
A residential pool heat pump commonly needs a dedicated circuit, and larger units draw enough that an older Guelph panel with no spare capacity needs work before the heater can be installed. Electricity in Guelph is distributed by Alectra Utilities, and electrical work falls under the Electrical Safety Authority.
We check the panel and the available capacity at the site visit, for the same reason we measure the gas meter before quoting a gas heater. Finding out at installation is expensive for everyone.
Placement matters more than for a gas unit. A heat pump needs a large volume of air moving through it, so it cannot be boxed into a corner, tucked under a deck or surrounded by shrubs. Air that has already been through the unit is colder than ambient, and a unit recirculating its own exhaust loses output for no other reason.
Running cost against a gas heater
Gas is billed by the cubic metre and distributed in Guelph by Enbridge Gas. Electricity is billed by the kilowatt hour on time-of-use or tiered pricing.
The comparison is not close on cost per unit of heat delivered, and it is not close in the heat pump's favour. Moving four to six units of heat per unit of energy drawn beats burning something at 83 percent efficiency by a wide margin, and the gap holds across any plausible rate.
What closes the gap in practice is time. A heat pump raises pool temperature slowly, typically over a day or more rather than in an afternoon, because it is limited by how much heat it can extract from the air. A gas heater will bring a pool up in hours. If the pool is used on a schedule that tolerates slow recovery, the heat pump wins on cost with no real downside. If the pool needs to be warm on demand, the gas heater is doing something the heat pump cannot.
The honest summary: the heat pump is cheaper to run, the gas heater is faster and weather-independent, and the right answer depends entirely on how the pool is used rather than on which is better.
What goes wrong with pool heat pumps
Heat pump faults are different from gas heater faults and are diagnosed differently.
Low refrigerant charge
The most common cause of poor output. A sealed system does not consume refrigerant, so low charge means a leak, and topping it up without finding the leak is a repair that fails again.
Iced evaporator coil
Usually low charge or restricted airflow rather than cold weather alone. A dirty coil, a failing fan motor or an obstruction around the unit will all do it.
Failed reversing valve
On units with a cooling mode. It sticks, and the unit runs in the wrong direction or in neither.
Fouled titanium exchanger
Guelph's hard fill water scales the water side, which shows as falling output long before it shows as a fault code.
Failed capacitor or contactor
The compressor hums and does not start, or the unit does nothing at all.
Diagnosis runs in the same order as it does on a gas heater: flow first, then air, then the refrigeration circuit. Restricted water flow will produce a fault that looks like a compressor problem.
Cost and timing
These are typical Guelph-area ranges, not a quote.
| Job | Typical range |
|---|---|
| New pool heat pump supplied and installed | $5,500 to $9,500 |
| Dedicated electrical circuit | $600 to $2,000 |
| Refrigerant leak diagnosis and repair | $500 to $1,500 |
| Capacitor or contactor replacement | $250 to $550 |
| Fan motor replacement | $500 to $1,100 |
| Titanium exchanger descale | $300 to $550 |
| Compressor replacement | Frequently uneconomic; quoted against replacement |
A compressor failure on a unit past about eight years old is usually the point at which replacement beats repair, because the compressor is most of the value of the machine. That is the same rule the homepage applies to gas heat exchangers, for the same reason.
Frequently asked
Is a pool heat pump worth it in Ontario?
How long does a pool heat pump take to heat a pool?
Why is my pool heat pump icing up?
Can I run a pool heat pump in May in Guelph?
Do pool heat pumps need a dedicated circuit?
Pool heater not working?
Considering a pool heat pump in Guelph? We will tell you what it will and will not do in May before you buy one. Serving Guelph and Wellington County.
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