# Designing Solar Into a New Commercial Build: Roof, Structure, Cables and Grid

Building solar into a new commercial project at the design stage is cheaper and cleaner than retrofitting later. Deciding roof pitch and orientation, allowing extra structural load, routing cables and starting the grid connection while the building is still on paper avoids costly rework and lets the array be sized for the building’s real demand.

## Why is it cheaper to design solar in from the start?

Adding solar to a finished building often means working around decisions already fixed: a roof pitched the wrong way, a structure with no spare load capacity, or cable runs that have to be surface-mounted after the fact. Doing the same work on the drawing board costs a fraction of the price and avoids disturbing a building already in use.

Designing it in also lets the array be sized properly. The architect and services engineer can match the roof layout and electrical design to the building’s expected demand from the outset, rather than fitting whatever a completed roof happens to allow.

## What should the design team allow for?

A few things repay early attention. Roof orientation and pitch decide how much the array generates, so a south-facing slope or a flat roof suited to mounting frames is worth planning for. The structure needs to carry the extra weight of panels and ballast, which is cheap to allow for in the frame design and expensive to add later.

The services design should reserve space for inverters and isolators, plan cable routes from roof to plant room, and leave room in the switchgear. Roof penetrations, fixings and fall-arrest points can be built in cleanly. On the grid side, the DNO connection process takes time, so an early application avoids the array being ready before permission to export is.

## How does funding fit a new build?

Funding a new-build array works much like a retrofit. You can buy it outright as part of the construction budget, use hire purchase or leasing, or fund it through a PPA with no upfront cost. Under a PPA the rate per kWh is guaranteed at least 30% below the grid, and the system becomes yours for £1 at the end of the term.

Coordinating this with the main contract takes a little planning, since the solar may be installed by a specialist rather than the principal contractor. Raising funding options during design, not after completion, keeps the choice open and the wiring and roof ready. As an introducer, we can bring in funders and installers to work alongside your project team.

## Frequently asked questions

**Is it really cheaper to fit solar during construction?**

Usually yes. Orientation, structural load and cable routes are set once at the design stage instead of being worked around later. Retrofitting means extra scaffolding, disruption and sometimes strengthening work on a building already in use.

**Can I still use a PPA on a brand-new building?**

Yes. A PPA can fund the array with no upfront cost, keeping capital for the rest of the build. The rate is guaranteed at least 30% below the grid and the system becomes yours for £1 at the end of the term.

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Source: [Designing Solar Into a New Commercial Build: Roof, Structure, Cables and Grid](https://ppafunding.com/guides/designing-solar-into-a-new-commercial-build) · Author: PPA Funding team · Updated: 2026-08-03

PPA Funding is an independent introducer operated by DVC Group Ltd (Companies House 10462808), Shrewsbury — not the funder, the installer or the maintenance provider. The service is free to use; a commission may be earned from a partner at no extra cost. Content is educational and is not financial or tax advice.