How it works, from first enquiry to switch-on
Four stages, and you can stop at any of them. Nothing is committed until you have seen real numbers for your own building and read the agreement in full.
1. Free desktop assessment
We start remotely. Give us the site address and a recent electricity bill, and we measure your roof from aerial and mapping data, model the array that would fit, and run the expected generation against your actual consumption pattern.
What you get back is indicative rather than final: system size, expected annual generation, the likely saving, and whether the site is a candidate for a funded agreement or better suited to purchase. It costs nothing, nobody visits, and there is no obligation at this stage or any other.
Most sites are assessed within a few working days. If the numbers do not work we will tell you that plainly rather than pushing you into a survey.
2. Survey, design and funding
If the desktop numbers stack up, a full site survey confirms them. A surveyor checks roof construction, condition and loading, shading from surrounding structures, the state of your incoming supply and where inverters and isolation would sit. This is the point at which indicative figures become firm ones.
Alongside the design, the funding route is settled. Either an energy investor funds the system and you buy the power it generates, or you buy the system outright. The differences are set out on our funding page.
Two pieces of paperwork are handled for you at this stage. A grid connection application goes to your regional network operator, since the network needs to know about new generation connecting to it. Connection sits within the industry framework overseen by Ofgem. Planning is usually not required. Rooftop solar on commercial buildings in England is generally permitted development, and the December 2023 amendment removed the previous 1MW cap. Scotland and Wales have their own rules, and listed buildings and conservation areas remain exceptions worth flagging early.
3. Installation
Installation is carried out by accredited UK engineers. Rooftop work happens from outside the building and is scheduled around how you operate, so in most cases the site carries on trading throughout. Typical single-site installations are measured in weeks rather than months, depending on system size and roof access.
One short planned shutdown is needed to make the electrical connection. That is arranged with you well in advance, and on sites where continuity matters, such as care homes or continuous production, it is planned around your contingency arrangements.
Commissioning follows: the system is tested, signed off, registered with your network operator, and monitoring is switched on.
4. Generation, monitoring and reporting
From switch-on the system generates into your building, reducing what you draw from the grid. Monitoring runs continuously, so underperformance is visible rather than something you discover on a bill months later.
Under a funded agreement, monitoring, maintenance, cleaning and insurance sit with the system's owner rather than with you. You receive performance reporting covering generation, savings and carbon reduction, which is generally what finance and sustainability reporting needs.
How long the whole thing takes
Assessment to switch-on is commonly a few months rather than a few weeks, and the variable is rarely the installation itself. Grid connection responses and internal approvals on your side are usually what set the pace. We would rather say that plainly than quote a timeline nobody can hold to.
Where Hawthorne fits
We are an introducer rather than an installer. We handle the assessment and the commercial side, then introduce you to an accredited funding and installation partner who designs, installs and maintains the system. There is no cost to you for our involvement, at any stage.
Related reading
- Commercial solar funding options
- Solar for warehouses and distribution centres
- Solar for manufacturing businesses
- Solar for schools and academies
- Solar for care homes
- What is a solar Power Purchase Agreement?
- Common questions about fully funded commercial solar
The first step
A free desktop assessment. We use your site address and a recent electricity bill to model what your roof could produce and what it could be worth. No site visit, no cost, no obligation.
Common questions
How long does the assessment take?
Most desktop assessments come back within a few working days. It needs your site address and a recent electricity bill, and it does not require anyone to visit.
Do we have to close while the system is installed?
Generally no. Rooftop work is carried out from outside the building and scheduled around your operation. One short planned shutdown is needed for the electrical connection, and that is arranged with you in advance.
Do we need planning permission?
Usually not. Rooftop solar on commercial buildings in England is generally permitted development, and the 1MW cap that used to apply was removed in December 2023. Scotland and Wales have their own rules. Listed buildings and conservation areas are the main exceptions, and those are worth raising at the first conversation.
What if the assessment says our site does not suit solar?
Then we tell you, and that is the end of it at no cost. A site that does not work is not a project we would want to push.