Rooftop solar PV designed around your building's load

A roof that fits 800 kWp is not automatically a roof that should carry 800 kWp. The financial case rests on self consumption, because every kilowatt hour used on site displaces an import at your full unit rate, while every exported unit earns a fraction of that.

The starting point is twelve months of half hourly data from your supplier. That shows the shape of the working day, the size of the overnight base load, and how weekends and shutdown weeks behave. Where half hourly data is not available, we work from bills, meter readings and your operating pattern instead.

Sizing to the load curve usually produces a smaller array than the roof could hold and a better return per pound spent. Where the roof has more room than the load justifies, the surplus can be brought into the case through storage, EV charging or an export contract, but only if those numbers stand up on their own.

A credible commercial proposal rests on four checks. The structural capacity and remaining life of the roof, the electrical route from the array back to the intake position, the grid connection position with the distribution network operator, and the fire and access strategy required by your insurer.

Roof age matters more than most buyers expect. A twenty five year system on a roof with eight years of membrane life left means paying twice to lift and refit the array. Where that is the case we say so at feasibility, and installers in the network can price a re roof and a solar installation as one programme.

NRG Solar carries out the desk assessment and manages the process. The design, the installation and the ongoing maintenance are delivered by a vetted installer from our network working in your region.

Anything beyond a very small system needs an application to your distribution network operator under Engineering Recommendation G99. The operator assesses the effect of your generation on the local network and either accepts the connection, accepts it with conditions, or offers a connection that requires reinforcement work at a cost.

Timescales are the part that catches programmes out. Allow a meaningful lead time between application and determination, and treat the answer as a gate on the installation date rather than a formality. Applications are submitted by the installer, and NRG Solar tracks the milestone so the project does not stall quietly.

Where the network cannot accept the full export, an export limitation scheme keeps the array within the accepted figure. That is often the pragmatic route, since a system sized to self consumption exports comparatively little anyway.

The assessment works from indicative UK commercial averages for installed cost, annual yield, import and export rates, system life and panel degradation. Installed cost per kWp falls as system size rises, and yield is adjusted for orientation, roof type and region. These are averages, not a quotation.

Two sites with identical roofs can produce very different results from the same assumptions, because payback is driven by how much of the generation is consumed on site. A single shift operation running five days a week is a different proposition from a cold store running continuously.

Every figure the calculator shows is displayed alongside the assumption that produced it, so your finance team can test the case rather than take it on trust. Real pricing comes from the installer after a site visit.

Rooftop work is generally undertaken without stopping production. The parts that touch operations are the crane or hoist positions, the cable route through the building, and the shutdown needed for the final connection at the switchboard, which is usually a matter of hours and can be scheduled out of production time.

Responsibility sits with the installer under their contract with you. They hold the design responsibility, the workmanship warranty and the accreditations. NRG Solar does not install, and does not sit between you and the contract.

What NRG Solar does carry is the matching decision. We only put forward installers we have vetted, and we stay involved through feasibility, proposal and survey so that the comparison you are making is a fair one.