Is my roof suitable?

You step out onto the pavement, cross the street and look at your house the way you never do: studying the roof. Would it take some panels? The half-faded sheet metal, the water tank up there, the neighbour's tree that grew more than it should have. Hard to tell from the pavement.

And yet you can work out much of the answer yourself, without anyone climbing up. Here's the guide to what to look at, in the order that matters.

We start here because it weighs the most and gets looked at the least.

A shaded panel generates far less, and the problem doesn't stop at that panel: depending on how the system is wired, shade on one module can drag down the output of several. That's why a "small" patch of shade is not a minor issue.

The usual suspects: the water tank, the aerial, your own tree or the neighbour's, a high party wall, the building next door. And one detail that slips by: shade changes with the seasons. In winter the sun sits lower and shadows stretch out. The corner that's in full sun in January can spend all of July in shade.

The at-home exercise: on a clear day, look at your roof at 10am, 1pm and 4pm. If the area where the panels would go is in sun at all three, excellent. If there's shade at some hour, that doesn't rule anything out either: we do the detailed study during the visit, with tools that simulate the sun's path across all twelve months of the year. Your look is so you arrive at that conversation knowing what's being discussed.

In Argentina, north-facing roofs get more sun across the year. That's the ideal. But from there to "if your roof doesn't face north, forget it" is an enormous leap.

A roof facing east or west generates less than one facing north, but the difference is moderate, not dramatic. It can even have an upside: a west-facing roof generates more in the afternoon, which is exactly when many homes consume most, with the air conditioning going and everyone back from work.

The genuinely difficult orientation is due south with a steep pitch. And even then, before ruling it out, we look at whether there's another roof plane, a flat surface where panels can be tilted on a frame, or even a usable pergola or outdoor room.

Sheet metal is very workable, and it's the most common case: fixing is direct and clean. Tile also works, with more care and a bit more labour. On a flat concrete slab we use a frame that gives the panels the tilt the surface doesn't have.

What really matters is the condition. Panels last around 25 years; if your roof needs repairs, it's worth doing them before installing, because dismantling and remounting the system to fix the roof underneath is an avoidable cost. Heavily rusted sheeting, loose tiles or a slab with leaks get sorted first. That isn't a rejection of the project: it's a question of sequence.

Each panel takes up a little over two square metres. A typical residential system runs between 4 and 12 panels depending on consumption, so we're talking about 10 to 30 m² of usable roof, after subtracting the shaded zone, the edges and any obstacles.

Roof not big enough? The project doesn't die: we look at the garage, the outdoor room, or a carport-style structure over the parking space, which also shades the car. We've done more than one where that shade was half the reason for the decision. The house roof is the natural candidate, not the only one.

Up to here, you can assess everything on your own. There's a part that requires a site visit, and it's worth knowing which part so nobody sells it to you as settled over the phone:

• The real condition of the roof structure and the fixing points
• The cable route to the distribution board, and the state of the board itself
• The precise shade study and the exact panel layout

That's why every quote is finalised with the visit: it's where these three points get verified. There's a separate article on what happens during the survey.

• Is the candidate area in sun at 10am, 1pm and 4pm?
• Which way does the roof face? (north ideal, east/west works, south needs study)
• What material is it and what condition is it in?
• Are there pending repairs worth doing first?
• Is there a plan B? (garage, outdoor room, parking space)

Most roofs are suitable. The right questions aren't "does it work or not?" but where the shade falls and at what hour, what condition the surface is in, and how many square metres are genuinely available.