Solar Panels on New Build Homes

What a new build brings to the job

New build roofs are, structurally, the most predictable we work on: trussed rafters at regular centres, a modern breathable membrane, dry-fix ridge and verge systems, and a covering with spares readily available. The electrical installation is current, earthing is conventional, and there is generally a sensible place to put an inverter.

The complications are almost all contractual and geometric rather than structural. Warranties, covenants, roof shape and the developer’s own installation are what shape the design.

Structural warranty and notification

This is the point to get right first. New homes are typically covered by a ten-year structural warranty, and those policies generally require the homeowner to notify the provider before alterations affecting the structure or the weathering envelope, and to use an appropriately certificated contractor with documentation kept.

An array fixed through the covering into truss members is exactly that kind of alteration. Handled in the right order — notify, install to the mounting manufacturer’s published method, retain the certification — it is a routine matter. Handled the wrong way round, a later roof claim can become a difficult conversation. We provide the documentation; the notification is the homeowner’s to make.

If the property is still within its initial defects period with the developer, that adds another party to inform.

Roof geometry

New build roofs look simple from the street and rarely are. Pitches are often shallower than on older housing, which lowers winter yield and slows self-cleaning. Roof planes are interrupted — rooflights, soil vents, mechanical ventilation terminals, half-hips, catslides over garages, and the small stepped planes that come with a varied elevation.

The result is a roof that measures well on plan and offers a much smaller clean rectangle in practice. Array layout gets drawn around what is actually up there.

Dry-fix verge and ridge systems also affect method: the perimeter details are proprietary components that need reinstating correctly rather than bedded and pointed.

Developer-fitted arrays

Many new homes arrive with a small array already fitted, sized to satisfy an energy calculation rather than to cover household demand, and sometimes placed on a slope chosen for compliance rather than sun. Extending one is common work.

The questions are whether the existing inverter has spare capacity and a free MPPT input, whether the existing string can be reconfigured with the new panels, whether panel electrical characteristics are compatible, and whether the combined system crosses 16A per phase — around 3.68kW single phase — which moves it from a G98 notification to a G99 application requiring approval before installation. Where an existing G98 system is being enlarged, that approval has to be in place first.

Sizing against a modern house

New builds increasingly come with an air source heat pump, mechanical ventilation and provision for vehicle charging. That changes the consumption profile the array is sized against — more winter electricity demand, more of it running through the day, and a stronger case for storage than an equivalent older house.

Access and limitations

Scaffolding is usually straightforward, though on dense developments there may be little space to stand it and shared driveways or communal parking to negotiate with a management company.

The honest limitations: shallow pitches produce less in winter, interrupted planes limit array size, and covenants occasionally restrict what can go on a road-facing elevation. Where the front is the sunny side and the covenant is restrictive, in-roof mounting with all-black panels is usually the design that gets agreed.