When a roof is unavailable, shaded or already full, the alternatives are a purpose built structure or a wall. Both cost more per kilowatt than a roof, because a roof is a structure you already own, and both are chosen for a reason beyond generation: covered parking, shelter, EV charging, or simply somewhere that faces the sun when the roof does not.
Carport solar panels: the carport is a structure first
A solar carport is a building with panels as its roof, so it is priced as a building: foundations, frame, drainage of the run off, and a wind and snow load calculation. The generation is the easy part. What makes them worth it is the second function: sheltered parking, an obvious place to put an EV charge point with a short cable run, and on commercial sites a visible statement that is also a car park upgrade. Planning is a real consideration because a carport is a structure in a way panels on a roof are not.
Solar canopy and pergola solar panels
A solar canopy over a terrace or an entrance and a photovoltaic pergola over a seating area are the domestic scale version, and they behave the same way: a structure that has to be designed for wind and snow, with drainage for the water that now runs off it, and a cable route back to the house. Semi transparent modules exist for pergolas and produce less per square metre in exchange for letting light through, which is usually the point. Expect the structure to cost more than the panels.
Wall solar panels and vertical arrays
Panels on a south facing wall produce less over a year than the same panels on a roof, because the angle is wrong for a British summer sun. They produce relatively better in winter, when the sun is low, which flattens the seasonal curve and can suit a household with a winter heavy load. Vertical bifacial arrangements on east west facing walls or fences generate in the morning and evening. These are niche answers to specific constraints, not general alternatives to a roof, and they need the wall's construction checked before anything is fixed to it.
The common thread: planning and structure
Everything in this category is a structure rather than an addition to one, so two questions come before design. Does it need planning permission, which for a new outbuilding or a structure in a front garden, a conservation area or on a listed curtilage is much more likely than for roof panels. And has somebody competent calculated the wind and snow loads, because a large flat surface on posts is exactly the thing that gets lifted in a storm when it was not.
Questions people ask about solar carport
Is a solar carport worth the cost?
On generation alone, rarely, because the structure costs more than a roof you already own. It becomes worthwhile when you also want the parking cover, an EV charge point with a short cable run, or usable space on a site with no suitable roof.
Do solar carports need planning permission?
More often than roof panels, because a carport is a new structure. Size, siting, whether it is in front of the house and whether the property is listed or in a conservation area all matter, so check before design.
Do wall mounted solar panels work?
They generate less than the same panels on a roof over a year, and relatively more in winter when the sun is low. They are a reasonable answer where no suitable roof exists, not a general alternative to one.
Can a pergola really generate useful power?
A modest amount, and semi transparent modules produce less again in exchange for letting light through. Treat it as a structure with a generation bonus rather than as a power project.