Solar rarely covers a building’s full demand, and it is not right for every site. Where the roof, the load and the funding line up it is one of the cleanest long-term reductions available. The variable that decides it is not the size of the roof, it is how much of what you generate you use yourself.
Verification
- Verified as at:
- Source:
- Omnium method; installed cost and export rates are market-dependent and modelled per site
- Last reviewed by:
- Omnium
Figures in this sheet were current at the verification date above. Regulated charges reset each April. If you are relying on a figure, check the source or ask us.
Designed A4 fact sheet, ready to print or circulate.
Self-consumption decides everything
A unit used on site avoids the full delivered price of a grid unit, including the network charges, levies and VAT that sit on top of the commodity. A unit exported earns only the export rate, which is a fraction of that.
So a self-consumed unit is worth several times an exported one. That single relationship drives the whole case, and it is why solar suits businesses whose demand happens in daylight: hotels, offices, factories, warehouses and leisure sites. A site that runs hard during the day and quietly at night will self-consume most of what it generates. A site whose demand is mostly after dark will export most of it and see a much weaker return.
We size against the half-hourly profile rather than against roof area. A system sized to the roof and not to the load produces a return that looks better on paper than it does on the invoice.
What we will not tell you
We do not publish an installed cost per kWp, an export rate, or a payback period on this page.
Installed cost moves with the market and with system size. Export rates vary by supplier. The delivered grid price a unit avoids depends on your contract, your network region and your capacity position. A payback figure built from three moving numbers, before anyone has seen your site, is a sales figure rather than an analysis.
We model all of it from your own data and show you the workings, including the assumptions we had to make and how sensitive the answer is to each one.
Generation in UK conditions
A well-oriented UK system generates in the region of 900 to 1,000 kWh per kWp per year. That figure is climatic rather than commercial, so it is more stable than anything on the cost side, but it still varies with orientation, pitch, shading and location.
The three funding routes
| Route | How it works | Suits |
|---|---|---|
| Capital purchase | You buy the system outright and own the asset and all the savings. | Businesses with capital available and a tax position that lets them use the allowances. |
| Asset finance or lease | You fund the system over a term. Repayments can be offset against the energy saving, so cash flow can be positive early. | Businesses wanting the asset without the upfront outlay. |
| Power Purchase Agreement | A third party funds, installs and owns the system. You buy the power it generates at an agreed rate for the term, often fifteen to twenty-five years. | Businesses wanting no capital outlay. |
A PPA removes the capital barrier but it is a long contract on your roof, and the rate, the escalator, the end-of-term position and what happens if you sell the building all matter more than the headline discount. We read the agreement before recommending one.
On tax relief
Capital allowances can materially change the net cost of a purchased system. Which allowance applies, and at what rate, depends on how the expenditure is classified and on the buyer’s tax position.
That is a question for your accountant rather than for us. We will model the case with and without the relief so you can see how much it matters, and we will not assert a tax treatment we are not qualified to give.
Where it does not stack up
- A site whose demand is mostly outside daylight hours. Most of the generation exports and the return weakens sharply.
- A roof that will need replacing inside the system life, or that cannot carry the load.
- A lease too short to see the return, or one that does not permit the installation.
- A site where cheaper reductions have not been done yet. Solar sized against unreduced demand is bigger and more expensive than it needs to be.
Related sheets
- Battery storage
Storage shifts load rather than reducing it. Where the value sits, and why this is the technology we most often advise against.
- The net zero roadmap
The order to decarbonise a building or portfolio in, and why measuring and reducing before generating and offsetting costs less.
- Network charges and agreed capacity
Why regulated network charges rose sharply in April 2026, and why the capacity you reserve is a lever most businesses have never pulled.
Take this sheet into a meeting
Solar PV is available as a designed A4 fact sheet, dated and set for printing or circulation.
If this sheet raises a question about your own sites, speak to us.