Heat pumps · Comparison
Heat pump or solar water heater?
Sonnen supplies both, so this is a comparison, not a pitch. Each suits different properties. Here is how they differ on the things that usually decide it: roof and space, night and cloudy-weather performance, running cost and property type.
The basics
How each one works
Solar water heater
Collectors on the roof capture solar heat. A sealed heat exchanger passes it to your water, and an insulated tank stores it for when you need it. An electric booster tops up automatically on cloudy days. Sonnen supplies thermosiphon systems (tank and collector both on the roof) and split systems (slim collectors on the roof, tank indoors).
Heat pump water heater
A fan draws ambient air across an evaporator, capturing heat. A compressor raises it to a useful temperature and a heat exchanger transfers it into your water. Our all-in-one units integrate the tank and the pump, and heat water day and night, independent of sunshine.
Side by side
Comparing the two
| Solar water heater | Heat pump water heater | |
|---|---|---|
| Energy source | Heat from the sun, captured by roof-mounted collectors, with an electric booster as backup. | Warmth drawn from the outside air, with electricity running the compressor and fan. |
| Roof and space | Needs roof area for the collectors (1.95 m² on our 185 L system, 3.90 m² on our 290 L system) and a roof that can carry them. A split system suits weak or steep roofs. | Needs no roof collectors. The all-in-one unit needs a position with access to air: outdoors (an IPX4-rated model is available) or, for tight spaces, a compact wall-mounted unit. |
| At night | Relies on hot water stored in the insulated tank during the day, with the electric booster as backup. | Heats water day and night, independent of sunshine. |
| Cloudy weather | The electric booster tops up automatically, so you still have hot water, but more of the energy then comes from electricity. | Not affected by sunshine: consistent output regardless of weather or time of day. |
| Running cost | The sun does most of the work whenever it's available; electricity is used only to top up. | Up to around 70% less electricity than a standard electric geyser. |
| Best suited to | Properties with suitable roof space and good sun exposure. Detached houses and apartments (our thermosiphon system suits apartments up to 3 floors below the rooftop). | Properties with limited or unsuitable roof space, tight installations, or hot-water demand through the night. Buildings with high, steady demand, such as hotels, schools and hospitals. |
Both cut water-heating electricity compared with a standard electric geyser. Which costs less to run at your property depends on your sun exposure, how much hot water you use and when you use it, which is why we look at your site before recommending either.
Which suits you
When each one is the better fit
A solar water heater tends to suit you if…
- You have suitable roof space and good sun exposure
- You want the sun to do most of the work, with electricity only as a top-up
- Your roof is weak or steep and you'd like a split system with the tank indoors
- Your supply is borehole or hard water: our indirect solar systems run on any water quality
A heat pump tends to suit you if…
- Roof space is limited, shaded or unsuitable for collectors
- You need hot water through the night and in any weather
- You're fitting into a tight space or an apartment, where a compact wall-mounted unit helps
- Your building has high, steady demand, as hotels, schools and hospitals often do
The two can also be combined. Our YT-200/250/300TB1 heat pump has an optional solar coil so it can pair with solar thermal, and larger sites can run a multi-energy hot-water plant that uses both.
Our recommendation
Sonnen will recommend the right one for your site
We look at your roof and available space, how and when you use hot water, your property type and your water quality, then recommend what the job needs, not a bigger or more complicated system than the demand justifies.
Heat pump water heaters
More on heat pumps
Get in touch
Not sure which suits your property?
Tell us about your site and how you use hot water, and we'll recommend the right one.