Installation
Access and scaffolding drive more of the price than the panels do
Modules are now among the cheaper parts of an installation, so the cost of a job is set largely by how difficult the building is to work on.
By Arjun Nair4 min read
Where the money in a quotation goes
People approach solar quotations expecting the panels to be the main expense, which was true once and is no longer. Module manufacturing has scaled enormously and the price per unit of capacity has fallen a great deal, while labour, access equipment, electrical materials and compliance have not fallen at all.
The result is a cost structure dominated by everything except the generating equipment. A typical domestic job pays for a crew for one or more days, an access system for at least a week, mounting hardware, an inverter, cabling and containment, electrical alterations at the consumer unit, and the administrative work of certification and notification.
This inversion explains a lot of otherwise puzzling pricing. It is why two identical arrays on two different houses can be quoted very differently, and why a quotation broken down by line item is far more informative than one expressed as a price per unit of capacity.
Access is a fixed cost, and fixed costs reward size
A scaffold doesn’t care how many panels it serves. Erecting and dismantling it, hiring it for the period, and the associated safety work cost much the same whether eight modules or twenty-four go up. The same is true of the crew’s travel, the mobilisation and most of the paperwork.
That fixed component is why cost per unit of capacity falls sharply as an array grows, and why very small installations look poor value. It is the strongest argument for filling the usable roof at the outset rather than starting small with the intention of adding later, because adding later means paying the entire access cost a second time.
It also argues against phasing an installation across years for budgeting reasons. The second phase will cost more than its share, the two systems may need separate notifications, and matching modules to the originals becomes difficult once a product line has moved on.
What makes a building expensive to work on
Height is the obvious factor, and storey count changes the scaffold specification more than a simple proportion suggests. Beyond that, awkward geometry does the damage: a conservatory or lean-to below the working area, a roof that can only be reached over a neighbour’s garden, a steep slope with no safe standing, or several small planes rather than one large one.
Ground conditions matter in ways nobody anticipates. A scaffold needs a stable base, so sloping ground, a light well, a flat roof beneath or a driveway that must remain usable all add complication. Restricted street access adds another layer, and in many towns using a pavement or a parking bay requires a licence from the local authority with its own lead time and fee.
Then there are the neighbours. Where a scaffold must stand on adjoining land, or where an array sits on a party wall boundary, agreement is needed and can’t be assumed. This is one of the more common causes of a job being delayed after everything else was ready.
The things that quietly add days
Cable routing is the most frequent. Getting from the array to the inverter and from the inverter to the consumer unit sometimes means an easy route through a loft and an airing cupboard, and sometimes means chasing walls, lifting floors or running surface containment through occupied rooms. The difference between those two situations is a day of work and a decorating bill.
Electrical works come next. An older consumer unit may not accommodate the new circuit, or the earthing arrangement may need upgrading before generation can be connected, and both are legitimate requirements rather than upselling. A quotation that assumes the existing board is fine, without anyone having looked inside it, is a quotation with a hole in it.
And then the surprises that stop work entirely: asbestos in an older outbuilding or in cement sheeting, a chimney in poor condition adjacent to the array, structural timber that turns out to be inadequate, or weather. Wind is the usual culprit, since roof work stops well below the wind speed at which most trades would carry on at ground level.
How to spend less without buying less
The most effective lever is combining the access with other work. If the roof needs attention, if a chimney needs repointing, if gutters need replacing, doing them under the same scaffold converts three separate access costs into one. That saving is often larger than any discount available on the equipment.
The second is scheduling. Installers are seasonal, and a job booked into a quieter period is easier to price keenly and less likely to sit waiting for a crew. This varies by market and it is worth asking directly when they are least busy.
The third is simply not buying complexity. Optimisers on an unshaded roof, a battery bought before the consumption data has been examined, an inverter sized for a future expansion that may never happen, a monitoring subscription. Each adds cost that does nothing for the yield, and a quotation that includes them without a stated reason deserves a question rather than a signature.
Common questions
Can the work be done without scaffolding?
Sometimes, using other access methods on lower or simpler roofs, and the choice belongs to the installer under the safety rules that apply to them. Be sceptical of a quotation that is cheaper specifically because access has been left out, since the saving comes from somewhere and working at height without proper provision is exactly where it comes from.
Is it cheaper to supply my own panels?
It rarely works out well. Installers buy at trade terms, warranty handling becomes complicated when the equipment came from elsewhere, and any certification scheme they belong to may restrict what they can install. The labour is where the money is anyway, so the saving on the components is smaller than most people expect.
Why do quotations vary so much for the same array?
Because they are pricing different amounts of work, and often different amounts of risk. One may include a consumer unit replacement, scaffold to the rear elevation and a full survey; another may assume the simplest possible case and issue variations later. Comparing totals without comparing scope is the commonest mistake in the whole purchasing process.
Staff writer, Power Your Roof
Arjun has been reporting on solar basics, batteries, bills & tariffs since long before it was fashionable and thinks most subjects are more interesting once you know how they work.
