Warehouse solar glossary
The terms that come up when you plan a warehouse solar project, explained in plain English, from half-hourly data and self-consumption to G99, TNUoS, the AIA, MEES and RC62.
- Clear-span steel-portal roof
- The dominant modern warehouse roof: a wide, column-free steel portal frame that gives a large, uninterrupted area for a rooftop solar array.
- Standing-seam / trapezoidal metal roof
- The two common profiled-metal roof types on industrial units. Each needs a specific non-penetrative clamp or clip so panels are fixed without piercing the weatherproof sheet.
- Non-penetrative clip-fix mounting
- A mounting system that clamps onto the roof seams or ribs rather than drilling through them, preserving the roof warranty and the weather seal.
- Ballasted array
- A flat-roof mounting method that holds panels down with weighted trays instead of roof penetrations, used where the structure and wind loading allow it.
- Half-hourly (HH) meter data
- The 48-readings-a-day consumption data from a commercial meter. Twelve months of it is the basis for sizing a warehouse array to real daytime load rather than roof area.
- Daytime base-load
- The steady floor of electricity a warehouse draws between order peaks (lighting, chargers, small power). Solar matched to it is self-consumed rather than exported cheaply.
- Self-consumption
- The share of generated solar used on site rather than exported. Higher self-consumption drives the return, because each on-site unit is worth the full grid price you avoid.
- DNO (Distribution Network Operator)
- The regional company that owns the local grid. It must approve any new generation connection and sets the timeline, which can run to 12-24 months for systems above 1 MW.
- G99 connection application
- The Energy Networks Association process for connecting generation above 3.68 kW per phase. Required for essentially every commercial rooftop array.
- G100 export limitation
- A control scheme that caps or prevents export to the grid, letting a larger array be installed where the DNO cannot grant a full export connection.
- TNUoS / BSUoS network charges
- Transmission and balancing charges levied on imported electricity. Both are rising, so every unit solar displaces is a growing saving and a hedge.
- PPA (Power Purchase Agreement)
- A zero-capital route where a funder owns the array and sells you the power below grid price. Well suited to tenants and shorter leases where capital purchase does not fit.
- AIA (Annual Investment Allowance)
- The £1m allowance giving 100% year-one tax relief on qualifying plant, which covers most warehouse solar projects. Note that solar is special-rate plant, so full expensing does not apply.
- 50% First-Year Allowance (special-rate pool)
- The relief that applies to solar spend above the AIA cap: 50% in year one, then a 6% writing-down allowance on the balance.
- MEES (Minimum Energy Efficiency Standards)
- The rules governing the minimum EPC a commercial building needs to be let. Currently band E, with a proposed uplift for larger buildings from 2031 that is not yet law.
- EPC / SBEM
- The Energy Performance Certificate and the modelling method behind it for non-domestic buildings. A solar array is captured in SBEM and typically lifts a warehouse one to three bands.
- The insurer-backed guidance on rooftop PV fire safety, covering panel clearances from sprinkler zones and firewalls, DC isolation and rapid shutdown.
- Sprinkler clearance
- The gap that must be kept between panels and sprinkler heads or fire-break zones so the suppression system still works. A common reason a naive roof-fill design gets rejected by insurers.
- Green-lease addendum (BBP toolkit)
- A set of lease clauses from the Better Buildings Partnership that shares the cost and benefit of solar between landlord and tenant, solving the split-incentive problem.
- MHE (materials-handling equipment)
- Forklifts, reach trucks and conveyors. Electrifying MHE adds daytime load that a solar array can serve, which improves self-consumption.
- 3PL (third-party logistics)
- An operator that runs warehousing and distribution on contract for other companies. Usually a tenant, so lease length and the split incentive shape the solar case.
- Embedded network / private wire
- A private distribution arrangement that supplies generated power directly to occupiers on a multi-let estate without using the public grid.
- BESS (battery energy storage system)
- On-site batteries that store surplus solar for use at peaks or overnight, raising self-consumption and enabling export limitation.
- Freeport Enhanced Capital Allowance
- 100% first-year tax relief on qualifying new plant installed within a designated Freeport tax site. A valuable extra for warehouses inside those zones.