For years, “solar water heater” meant roof collectors. Today there is a strong competitor that does not need to be on the roof at all. Both can cut water heating costs. Which suits you depends on your house, your climate and what you pay for energy.
What each one does
A heat pump water heater works like a refrigerator in reverse. It pulls warmth from the surrounding air and moves it into the tank. It uses roughly a third to half the electricity of a standard resistance tank, which is another way of saying that every unit of electricity delivers two to three units of heat, depending on conditions. It sits indoors, often in a basement or utility room.
Solar thermal collectors capture the sun’s heat on the roof and send it through a closed glycol loop to a tank. Once the equipment is paid for, the energy is free, but it is only available when the sun is out. A well-sized system commonly supplies about half of annual water heating energy. For the mechanics, read how solar hot water works.
Side by side
| Heat pump water heater | Solar thermal system | |
|---|---|---|
| Energy source | Electricity plus ambient heat | Sunlight, with backup heater |
| Where it lives | Indoors | Roof plus indoor tank |
| Works at night and in winter | Yes, with some limits | Reduced in winter |
| Upfront cost | Moderate | Usually higher |
| Installation | Often simple | More plumbing and roof work |
| Moving parts | Compressor, fan | Pump, valves, controller |
| Roof needed | No | Yes |
| Noise | Some, like a quiet fan | Very little |
A worked example
Say a household’s electric tank uses about 4,000 kWh a year to heat water. That is an illustrative figure, so substitute your own from your bills. A heat pump water heater would do the same work on roughly 1,300 to 2,000 kWh, saving something like 2,000 to 2,700 kWh. A solar thermal system supplying half would save about 2,000 kWh, but it needs a roof, a loop and a controller, and it saves mostly in summer. Over the year the two can land closer together than you might guess, which is why the install cost and the roof often decide it.
If you heat water with gas instead, the comparison changes: a heat pump swaps gas for electricity, so your local gas and power prices matter a lot. Run the numbers on your own bills, not the brochure.
Climate and placement
A heat pump water heater needs air, ideally in a space that does not drop too cold. In a chilly unheated basement it can struggle, and it also cools the room slightly, which is a small bonus in summer and a small cost in winter. Many models include an electric backup mode for tough days, and some need clearance or a drain nearby.
Solar thermal is happiest with a sunny, unshaded roof and a household that uses plenty of hot water in warm months. In deep cold, evacuated tubes tend to hold up better than flat plates, and the antifreeze loop needs periodic checks. The winter performance guide covers how collectors behave when it gets cold.
The best of both worlds
You can combine them. A heat pump water heater powered, in part, by your own solar panels gives you efficient heating and clean electricity at once. In daylight it runs on free power, and in provinces with generous export credits it can draw on banked summer surplus in winter. For many homes, that pairing is simpler and more flexible than thermal collectors, because the panels also serve everything else you plug in. We go deeper on sizing in heat pump and solar panels together.
How to decide
- Is my roof good for solar at all? Use the roof checklist.
- Is my current water heater gas or electric? Replacing an electric resistance heater with a heat pump often saves the most.
- Do I have a suitable indoor spot, with enough space, a drain and reasonable room temperature?
- Do I have panels already, or plan to?
- What do the quotes say, line by line? See what a solar hot water system costs for typical components.
Don’t forget the electric bill
A heat pump pulls power from the grid, so its running cost depends on your electricity rates, and time-of-use plans can reward running it off-peak. Heat pump programmes and rebates have been reported in some provinces, but terms shift, so verify them with your utility rather than relying on any old article.
Sizing and installation notes
A family of four typically wants a tank in the range of 180 to 300 litres, whichever technology you pick, and the tank should be sized to your real peak use, not to the brochure. Both options need a licensed plumber and, for the heat pump, an electrician and a suitable circuit. Permits and inspection are normally required, so confirm that your installer pulls them.
Where this leaves you
There is no single winner. For a sunny roof and a large hot water appetite, solar collectors still earn their keep. For many other homes, a heat pump water heater, with or without panels, is the easier path. Compare it with solar panels before you commit, and browse the hot water and heating hub for related guides.
Quick answers
Is a heat pump water heater better than solar hot water?
It depends on your roof, climate and fuel prices. Heat pump units are simpler to install, while collectors suit sunny roofs and large hot water use.
Can I run a heat pump water heater on solar power?
Yes. Solar panels can supply much of its electricity during the day.