Sizing a Residential Solar Array on a Real Roof

Every Installation Is a Custom Plan

Switching to solar power is easy to do, but every enrollment is basically a custom plan. Local climate, power regulations, the shape of the roof and the household's actual energy consumption all need to be factored in when choosing a solar panel solution. The mistake most quotes make is starting from the target kW instead of starting from the roof.

Start with the Obstructions Not the Ridge

Mark the chimneys, vents, roof windows, dormers and setback lines first. What is left is your usable plane. Fit full rows into the clean areas before deciding whether any part-rows are worth the extra labour and cable.

Then Choose the Module Width

On a fragmented pitched roof, module width matters more than module wattage. The TTM 530-550 W is 1134 mm wide against 1303 mm for the higher-power platform, and that difference is often the reason an extra full row fits. Length is 2279 mm, so check your rafter run before committing to portrait rows.

Check the Load and the Lift

Each module is 32.2 kg - a two-person lift on a ladder. Aluminium alloy racking is specified to decrease pressure on the roof compared with heavier alternatives, but the total array load still depends on your module count, so confirm it against the roof structure rather than assuming.

Plan the Cable Before You Order

Order 300 mm cables for portrait rows and 1200 mm for landscape. This is decided at order, not on site. Getting it wrong means the crew spends the install managing slack or stretching connections.

Account for Shading in the String Plan

With 3 or 6 bypass diodes per module, group the modules that will be shaded by the chimney into the same string rather than spreading them across all strings. That contains the loss to one string instead of degrading all of them.

Consider Tilt on a Shallow Roof

At high latitudes, a shallow roof pitch wastes usable irradiance. Tilted frames raise the array to a useful angle, as on the Norwegian rooftop in our project portfolio - at the cost of extra wind load, which the racking layout then has to handle.

Round to Whole Cartons

Modules pack 31 per carton. Once you have your module count, round up to a whole carton rather than ordering a part-filled one.