People often use “solar” as one word, but a roof can host two very different technologies. One makes electricity. The other makes heat. Which one suits you depends on where your household energy actually goes, and on what your roof can hold.
The short version
Photovoltaic (PV) panels turn sunlight into electricity. That power runs lights, appliances, a car charger or a heat pump, and any surplus can usually be exported to the grid. Solar thermal collectors capture sunlight as heat and send it to a storage tank for showers, laundry and dishes. The first is a general-purpose power source. The second does one job.
Efficiency: heat is easier to capture
Collectors convert a larger share of the sunlight that lands on them into useful energy than panels do, because heat is a simpler product to harvest. A good panel is roughly 20 to 23 percent efficient, and collectors can beat that comfortably on a sunny day. But a kilowatt-hour of heat and a kilowatt-hour of electricity are not equal in usefulness, so a raw efficiency comparison can mislead. Electricity can also be turned into heat very efficiently by a heat pump, which changes the maths considerably.
Side by side
| Solar panels (PV) | Solar water heating | |
|---|---|---|
| Output | Electricity | Hot water |
| Roof space | More for the whole house, little if only feeding a heat pump tank | A few square metres of collector |
| Typical upfront cost | Higher in total, covers the whole house | Lower in total, covers water only |
| Moving parts | Almost none (inverter) | Pump, valves, controller |
| Maintenance | Light | A bit more, including fluid checks |
| Winter output | Lower, still useful | Lower, depends on design |
| Flexibility | High | One job only |
| Surplus to grid | Often possible | No |
A worked example
Take a family of four with an electric tank. Water heating in a home like that commonly takes somewhere around 3,000 to 5,000 kWh a year, though your own bills will tell you better. A well-sized solar thermal system commonly supplies about half of annual water heating energy, so call it 1,500 to 2,500 kWh a year, with most of it arriving between April and October and very little in December.
Now the panel route. A kilowatt of PV in southern Canada often yields roughly 1,100 to 1,400 kWh a year. Two kilowatts of panels, about five modules, would therefore make something like 2,200 to 2,800 kWh. Those kilowatt-hours do not have to go to the water heater. They offset whatever you use, and in provinces where exports earn bill credits they can be banked for winter. If the tank is also a heat pump water heater, which uses roughly a third to half the electricity of a resistance tank, the household needs far less power for the same hot water.
None of these numbers is a quote. They show why the answer shifts with your actual usage.
When solar hot water makes sense
Collectors earn their keep where hot water use is high and steady: a big family, frequent laundry, a pool or a hot tub. They also suit homes whose water heater runs on expensive fuel, and homes with a good south-facing patch but not much roof to spare. Expect a more involved install, with roof penetrations, glycol-filled piping in cold climates and a controller to commission. The cost of a solar hot water system is worth reading before you ask for quotes.
When panels make sense
Panels make more sense if you want to cut electricity bills across the board, or if an electric vehicle or heat pump is on your horizon. They are also simpler to live with: little to service, and your utility’s rules on credits decide how well surplus summer power helps in winter. At the time of writing, installed prices run roughly $2.50 to $3.80 per watt before incentives (CAD), so a 6 to 8 kW system lands in the mid-teens to high-twenties of thousands. Our overview of solar panel costs in Canada goes through what sits in a typical quote.
The twist: panels plus a heat pump water heater
A growing alternative is to run panels and a heat pump water heater together. The panels make electricity; the heat pump uses a small amount of it to make a lot of heat. That pairing often competes well with a dedicated thermal system, with no glycol loop on the roof and a tank that works at night. We compare the two head to head in heat pump vs solar water heating, and look at sizing in heat pump and solar panels together.
Checking your roof first
Either technology needs a roof that is sound, reasonably unshaded and facing roughly south. Work through the roof suitability checklist before anyone climbs a ladder. Collectors and panels also compete for the same good patch, so decide which job gets the prime spot.
So which one first?
If you are unsure, look at your bills. Where does the money go? Water heating typically takes a meaningful slice, but space heating and general electricity may take more. A home energy audit can tell you before you spend anything on equipment, and a cheaper fix such as insulating the tank and pipes may shift the answer.
Hot water projects of both kinds sit in our hot water and heating hub, a good place to compare the options side by side. Whatever you pick, confirm which provincial rebates are open this month, because they change often and the federal grant that used to exist is no longer taking applications as far as we know.
Quick answers
Is solar PV or solar hot water better?
Neither is better for everyone. Panels are more flexible, while solar hot water is efficient for heating water in homes with large hot water use.
Can solar panels heat water?
Yes, indirectly: panels can power an electric or heat pump water heater.