UK commercial solar glossary

The Energy Networks Association (ENA) rule for the smallest grid connections. It covers up to 16A per phase: about 3.68kW on a single-phase supply or 11kW on three-phase. The installer tells the network operator after the system is switched on. There is no need to apply first, because the system is so small.

The ENA rule for anything bigger than G98. You must apply to the network operator and get its approval before you connect. Larger systems also need a technical study, which can bring extra costs or a wait for grid upgrades.

The firm that owns the local power lines and substations in your area. UK Power Networks and National Grid Electricity Distribution are two examples. The DNO handles G98 and G99 requests and tells you how much spare grid capacity a site has, if any.

The UK scheme that certifies small-scale renewable installers and products, including solar panels. Many funders, insurers and export tariffs ask for an MCS-certified installer, so it is worth checking. It pays to check this before you invite quotes.

The MCS standard for fitting solar panels. It sets rules for design, fixings, electrical safety and hand-over papers. Naming it in your spec means every installer prices the same quality of work, while also giving you a standard to check against.

An Ofgem scheme that makes some electricity suppliers pay you for power you send to the grid. It covers solar, wind, hydro, anaerobic digestion and micro-CHP, up to 5MW. Each supplier sets its own rate. The only rule on price is that it must be above zero.

The old government scheme that paid small generators for the power they made and exported. It closed to new applicants on 1 April 2019. Sites already on it keep being paid until their term ends, and the rates rise with inflation.

Using the same land for solar and farming at once. Sheep may graze under the panels, or crops may grow between the rows. The field keeps producing food while it also makes power and income.

A deal where a third party pays for, owns and runs a solar system on your roof or land. You buy the power it makes at an agreed price, usually below what your supplier charges. Terms often run for 10 to 25 years. You pay nothing up front.

A tax relief that lets a business deduct the full cost of plant and machinery from its profits in the year it buys it. The limit is £1 million a year. Solar counts. However, the £1 million is shared across all of that year's plant spend.

HMRC classes solar panels as special rate spend (manual CA22335). That means they cannot use 100% full expensing. Spend above the AIA can get a 50% first-year allowance, but only companies can claim it. What is left goes into the special rate pool and is written down at 6% a year.

Solar panels on frames set into open land rather than on a roof. It suits sites with little or weak roof space, and it is the usual choice for solar farms. A ground-mounted scheme of any size will almost always need planning permission.

Rooftop solar means panels fixed to an existing roof. It is the most common kind of commercial solar. BIPV, or building-integrated PV, is different: the panel takes the place of a roof tile, wall panel or glass, and makes power as well.

kWp (kilowatt-peak) is a panel's rated output in standard test conditions. It is how system size is quoted. kW is the power being made or used at a given moment. A system's kW output changes with the sun and the heat, and is nearly always below its kWp.

The share of the solar power you use on site as it is made, rather than export. Power you use yourself saves the full price you would pay your supplier, while exported power earns much less. So a higher share of self-consumption usually means a faster payback.

The rate you are paid for solar power you send to the grid. Since the Feed-in Tariff closed, this is usually a Smart Export Guarantee rate set by your chosen supplier. Under a private PPA, the parties can agree a rate of their own.

Natural England's grading of farmland, from Grade 1 (excellent) to Grade 5 (very poor). Grade 3 is split into 3a and 3b. Grades 1, 2 and 3a are known as best and most versatile land. Planning policy tries to steer solar farms onto lower grades.

Rights that let some building work go ahead without a planning application. Much rooftop solar on business buildings falls under them, within limits on height and on listed or protected sites. The rules for ground-mounted panels are much tighter, so most solar farms need full consent.

The panel capacity (DC) divided by the inverter's output rating (AC). It is also called the inverter loading ratio. Commercial systems often run at about 1.1 to 1.3. That is because extra panels cost less than extra inverter, and the small loss at peak sun is usually worth it.

The box that turns the direct current (DC) from the panels into the alternating current (AC) your building and the grid use. Most systems need a new inverter once or twice in their life. Plan for it in your long-term budget.

How fast a panel's output falls over time. For modern silicon panels it is often about 0.3% to 0.5% a year. Makers' warranties commonly promise 80% to 90% of the first-year output after 25 years. Any payback model should allow for it.

The lasting weight that panels, frames and cables add to a roof or frame. A structural survey checks that the roof can carry it. This check often decides whether a site is in or out, since a weak roof stops the project.

A UK duty on quoted companies and large unquoted companies and LLPs to report their energy use and emissions in the annual report. Size is judged by the Companies Act test. For financial years starting on or after 6 April 2025, a company is large if it passes two of: over £54m turnover, over £27m balance sheet, over 250 staff.

A way for investors, lenders and buyers to judge how a firm treats the planet, its people and its own governance. On-site solar is often cited as evidence under the 'E'. Still, it sits alongside legal duties such as SECR, not in place of them.

The point where an organisation has cut its emissions as far as it can and balances the rest with removals. Solar is one tool for getting there. It works best with energy saving, storage and green power buying, and is rarely enough on its own.