Can your factory roof and production load justify solar panels?

Assess factory solar against production-time electricity demand, roof condition and the connection route before comparing funding. The standard G98 microgeneration threshold is 16 amps per phase; larger generation normally follows G99 [S1]. A large sheet roof does not establish its structural capacity or your export allowance. Model shutdowns as well as normal shifts. Checked October 2026.

Last checked 17 October 2026

Solar panels on your UK factory roof are worth assessing when generation matches production-time electricity demand and the roof is suitable [S3]. Cost the installation alongside roof works and the network connection, rather than treating roof area as a quote [S1], [S3]. Use the commercial solar cost hub and the explicitly assumed example below to frame a site-specific tender.

Is your factory roof suitable for solar panels?

Commission the roof assessment before treating roof area as generating capacity. Give the surveyor roof age, repair records, original drawings and the asbestos register where available. Ask for an assessment of sheet condition, steel deck, fixings and supporting structure. Record the proposed mounting loads and the roof’s remaining serviceable condition [S3].

HSE lists fibre-cement sheets, corroded metal sheets, rooflights and liner panels among potentially fragile surfaces. Staff should not walk a roof to count panels or take measurements without a safe system of work [S2]. Request a survey method and a priced access plan from competent contractors.

If replacement is needed, compare reroofing with and without solar. Include removal and reinstatement during later repairs in the tender. The engineering review should cover wind loads, penetrations and the proposed cable route. Use warehouse solar for comparison where your building is primarily storage.

How much electricity could solar replace during your shifts?

Create separate demand profiles for normal production, reduced shifts and shutdowns. Identify process loads, compressors, refrigeration and ventilation in the readings rather than inferring them from your annual bill. BRE’s commercial guide links solar design to electricity consumption; the useful output is generation your site can consume when it is produced [S3].

A continuous manufacturing scenario may absorb more midday generation than a factory that closes for maintenance in summer. That is a modelling question, not a sector-wide percentage. Put weekend and holiday export into the calculation. If you are electrifying heat or adding fleet charging, ask for a second design that shows the timing of those loads.

The business solar hub sets out the overall process. Compare your contracted unit cost with business electricity price data, without treating a national average as your next contract price.

What does the G99 application need to cover?

A distribution network operator (DNO) assesses the electricity network connection. Engineering Recommendation G99 is the connection standard normally used above the G98 microgeneration threshold of 16 amps per phase. That corresponds to 3.68 kilowatts (kW) on single phase or 11.04 kW across three phases. Kilowatts measure power; kilowatt-hours (kWh) measure energy [S1].

Provide existing generation, proposed inverter ratings and any battery details. Export permission and panel peak capacity are different quantities. Ask the designer to obtain the agreed connection conditions before energising the system; an export restriction does not itself remove the application requirement [S1]. See how to apply for G99.

What is the factory solar payback under different funding models?

An illustration, not a quote. These are deliberately labelled assumptions for a manufacturing building. No yield, electricity price, contract share or installed price below is a measured result or an offer. “kWp” describes the panels’ peak power. Review the solar cost hub alongside a site-specific tender.

Generation × direct-use fraction gives on-site kWh. Multiply those units by £0.22; multiply remaining units by £0.05. Add them for gross energy value, then deduct £2,000 for annual net benefit. This benefit includes avoided electricity purchases alongside export cash. It excludes fixed supply charges.

For fully funded, assume the equipment owner sells power consumed on site at 22p, exports at 5p, meets operating costs and pays your 10% cash share. There is no extra electricity discount in this scenario. For part funded, assume an agreement gives you 60% of net benefit. Neither agreement is an actual offer.

Redo the mid case: 144,000 × £0.22 + 36,000 × £0.05 − £2,000 = £31,480. Your assumed part funded allocation is £31,480 × 60% = £18,888. Simple return on investment (ROI) divides annual net benefit by your capital and multiplies by 100. Payback in years divides capital by annual net benefit.

Roof renewal, grid connection, supply upgrades, storage and EV charging equipment are additional. VAT, grants, tax relief, borrowing, output degradation and replacement costs are excluded. Ask your accountant to check the tax basis before using the figures in a budget.

What changes the tax, reporting and PPA decision?

The main Climate Change Levy electricity rate from April 2026 is £0.00801/kWh [S4]. Check whether your actual bill uses that rate, a reduced rate or an exemption. Do not add a separate levy benefit if your assumed avoided unit cost already includes it. Check the treatment with your accountant; see the levy explanation.

Energy Savings Opportunity Scheme (ESOS) duties depend on organisation and group eligibility [S5]. Streamlined Energy and Carbon Reporting (SECR) has separate reporting requirements [S6]. Retain generation, imported energy and exported energy records for your reporting team; installing panels does not complete either compliance task.

HMRC’s guidance excludes solar from full expensing and explains the conditional special-rate allowance [S7]. A fully funded PPA instead involves buying output under negotiated terms. The solar roadmap identifies long-term commitments and counterparty credit as commercial considerations [S8]. Request indexation, minimum purchases, shutdown treatment, insolvency rights, roof repair liability and end-of-term removal terms. Have your accountant and solicitor review the proposal before signing.

What is the next step for your manufacturing site?

Use the site check with production readings and roof records. Compare the different demand patterns in offices and care homes, then get matched with an installer that covers your area.

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