Is your roof a good fit for solar?

You do not need an engineer to get a first answer. A slow walk around your house on a sunny day, with a phone in hand, tells you more than most people expect. This checklist belongs to our installation and installers hub, and it works for panels as much as for hot water collectors.

1. Which way does the roof face?

In the northern hemisphere, a roof facing south collects the most. East and west faces still work, usually producing somewhat less over the year, and a pair of them spreads output across the day. North-facing slopes are rarely worth using. Use the compass on your phone, and if you have several slopes, note each one.

2. How steep is it?

Anything from a low slope to a fairly steep pitch can work. Flat roofs are fine too, because installers tilt the equipment on frames. Do not worry about getting the angle perfect. Small differences cost you a few percent, not half your output. In Canada a steeper tilt also helps snow slide off, which is a small bonus in February.

3. What shades it?

Shade is the real villain. A tree, chimney or neighbour’s tall house can cut production far more than a slightly wrong angle. Look at the roof at three times: mid-morning, noon and mid-afternoon. In winter the sun sits low, so shadows stretch much longer than they do in June. Ask yourself:

• Does the same spot stay shaded for hours?
• Will that young tree you planted ten years ago be taller in ten more?
• Is the shade on one corner, or across the whole roof?

Partial shade is not always a deal-breaker. Panel-level electronics handle patchy shade better than older string layouts, and our look at string inverters against microinverters explains the difference. Still, mention every shadow when you talk to installers.

4. How old is the roof?

Solar equipment lasts decades. Shingles may not. If your roof needs replacing within roughly five to eight years, replace it first or at the same time. Taking panels off and putting them back later costs real money. The material matters as well, and solar and roof types covers shingle, metal, tile and flat roofs one by one.

5. Can the structure carry it?

Panels are lighter than they look, but the framing underneath still has to be sound. A professional will check rafters, signs of sagging and how the roof is attached. In snowy regions the roof also has to carry the snow load on top of the equipment, which is another thing you cannot judge from the ground.

6. What is the electrical side like?

Older homes sometimes have a small main panel or ageing wiring, and an upgrade may be needed. It is common, and it should show up clearly on a quote. Installation also needs a permit and an electrical inspection, so expect paperwork either way.

7. Do you use enough energy at the right times?

Solar works best when your use lines up with the sun. A typical Canadian household uses somewhere around 9,000 to 12,000 kWh a year, though a home with electric heating can use much more. In southern Canada, each kilowatt of panels often makes roughly 1,100 to 1,400 kWh a year, depending on location and design. Treat that as a typical range, not a promise.

A worked example

Suppose a two-storey house uses 10,000 kWh a year and has a south-facing slope with room for about 40 square metres of panels. A system of around 7 kW could plausibly produce 7,700 to 9,800 kWh at those yields, which is most of the annual use. If the same house had only an east-facing slope with a large maple on one side, the answer would shift: perhaps a smaller system, fewer panels in the shaded corner, and a longer payback. Our guide on how many solar panels you need walks through the sizing arithmetic step by step.

Snow, wind and the Canadian roof

A roof that suits solar in Victoria may need different thinking in Winnipeg. Heavy snow loads, ice dams at the eaves and strong prairie winds all affect how racking is chosen and how far panels sit from the roof edge. None of this rules a roof out. It simply belongs in the conversation with your installer, who should be able to say what the local building code requires.

If the roof is not suitable

Do not give up yet. Options include a ground mount in the yard, a garage or shed roof, or working on efficiency first. A home energy audit is often the cheapest next step, since lower use means a smaller and cheaper system later. If you rent or live in a condo, the rules are different again.

What to bring to the first conversation

• Photos of every roof slope, taken in daylight
• Your last twelve months of electricity use
• The approximate age and material of the roof
• A list of nearby trees and buildings that shade you
• A note of any plans: a heat pump, an electric vehicle, a new roof

With that, a quote becomes a conversation rather than a sales pitch. For what to ask next, see choosing a solar installer. Prices and rules change, so check anything you read here against your own quotes and your utility’s current terms.