Plain English
The words in a solar and battery quote
Twenty terms, defined the way we use them on this site — each one with the page that puts it to work. If a quote from anyone uses a word that is not here, ask them what it means.
In short
Four of these decide most quotes: the kWp of the array, the G98 or G99 paperwork the inverter needs, the export rate you would be paid for what you do not use, and PAS 63100, which decides where a battery can go. The guides on each are linked from the definitions.
- kWp (kilowatt-peak)
- The rated output of a solar array under standard test conditions — the size of the system. A typical domestic array is a few kWp; what it actually makes in a year depends on where it is and which way it faces. how a system is sized →
- kWh (kilowatt-hour)
- A unit of electricity — what your bill counts and what a battery stores. A 1 kWp array in the South East makes somewhere between about 857 kWh a year (the conservative MCS figure our calculator uses) and the PVGIS model for a south-facing roof. the calculator →
- Inverter
- The box that turns the direct current the panels make into the alternating current the house uses. Its rated output per phase, not the number of panels, decides whether the installation is a G98 notification or a G99 application. G98 or G99 →
- Hybrid inverter
- One inverter that handles both the panels and a battery. A stacked assembly like the Sigenergy puts the inverter and the battery modules in one position on the wall; other lines pair a separate battery inverter with the array. the lines we fit →
- AC-coupled battery
- A battery with its own inverter, connected on the house side of the existing solar inverter. It is how a battery is usually added to panels that are already on the roof, when the existing inverter cannot take one directly. adding a battery to existing panels →
- DNO (distribution network operator)
- The company that owns the local cables and substations, as distinct from your supplier. On our patch it is UK Power Networks for most of Sussex and the eastern Surrey edge, and Scottish and Southern Electricity Networks for Chichester, Billingshurst, RH20 and the western Surrey towns. two operators, one county line →
- MPAN
- The 13-digit Meter Point Administration Number on your electricity bill. Its first digits say which network operator serves the address, which is why we read the operator from the MPAN and not from the postcode — the boundary between operators is not tidy.
- G98
- The Engineering Recommendation covering an inverter rated at up to 16 amps per phase — 3.68 kW on a normal single-phase supply. It is a notification: the system is installed and commissioned, and the network operator is told afterwards. G98 or G99 explained →
- G99
- The route for anything above 16 amps per phase. An application goes to the network operator before the inverter is energised and the system waits for approval; a battery inverter can take a job from G98 to G99. G98 or G99 explained →
- Smart Export Guarantee (SEG)
- The scheme, launched on 1 January 2020, under which SEG licensees pay small-scale generators for the electricity they export. Licensees set their own rates, which must be above zero; the rate current in our tariff reference was 12p per kWh as at June 2026. what exporting pays →
- Export meter / half-hourly data
- SEG payments are calculated from export meter readings, so a smart meter that records export half-hourly is part of the eligibility. The same half-hourly data, where the meter will share it, is what we size a battery from. sizing from your bill →
- Self-consumption
- The share of what the panels make that the house uses itself rather than exports. Without storage a typical home manages somewhere around half — our model assumes 48% — and with a battery sized to the evening load the model moves to 85%. is a battery worth it? →
- PAS 63100:2024
- The British Standards Institution fire-safety specification for battery storage in homes, published 20 March 2024 and required by the wiring regulations for batteries in dwellings since April 2026. It governs the location of the stack, the clearances around it and the detection near it. where a battery can go →
- BS 7671 (the wiring regulations)
- The standard every circuit we add or alter is certificated against. Its 2026 amendment added a chapter on stationary battery installations and requires home batteries to be installed to PAS 63100.
- Permitted development (solar)
- The national rules under which roof-slope panels on a house need no planning application, including inside a conservation area or a National Landscape. What they exclude is a panel on a wall or balcony fronting a highway, a flat-roof array without prior approval, and anything on a listed house. planning permission in Surrey →
- Prior approval (flat roofs)
- The lighter planning step a flat-roof array needs on designated land — a conservation area, a National Park or a National Landscape — before it goes up. In Brighton, where ballasted flat-roof arrays do a lot of the work, it comes up on most jobs. solar panels in Brighton & Hove →
- Conservation area / Article 4 direction
- A conservation area is designated by the council for its special architectural or historic interest; an Article 4 direction removes some permitted development rights inside one, so that particular street features are protected. Roof-slope panels usually stay permitted; a visible enclosure on a front wall may not. the Dorking example →
- Listed building consent
- The consent a listed house needs before anything goes on the roof — and, for a battery, sometimes for the position of the stack and the route of its cables even though the outside is untouched. We put a drawing to the conservation officer before we quote. the Lewes example →
- PVGIS
- The European Commission’s photovoltaic geographical information system, which models what an array at a given place, pitch and orientation will make. We publish its figures for a south-facing 4.5 kWp array at 35° with 14% system losses: about 1,037 kWh per kWp at Dorking, 1,125 at Washington and 1,177 at Lewes. the Surrey worked example →
- Consumer unit
- The fuse board. On a pre-war house it is often the real constraint on a solar or battery job — whether it has anywhere left to go, and what the earthing arrangement is — which is why the survey looks at it before the roof. general electrical work →
- Time-of-use tariff
- An import or export tariff whose rate changes by time of day — a cheap overnight window for charging a car or a battery, or a higher export rate in the 4–7 pm peak. A time-of-use export rate only earns its peak on electricity you can export in that window, which in practice means a battery. export tariffs compared →
- Retention point (cycle life)
- The percentage of original capacity a battery cell is warranted to keep after a stated number of cycles at a stated temperature. A bigger cycle number is only a better warranty if the retention point and the temperature are the same. how to read a warranty →
- Performance warranty
- The promise, usually on panels, that output will still be at least a stated share of the original after a stated number of years — a curve rather than a cliff, and a different promise from the product warranty against defects. how to read a warranty →
- Load-managed charger
- An EV charging point that watches the incoming supply and eases off rather than tripping the main fuse when the oven and the shower are running at the same time — which matters more in an older Sussex property than in a new build. sizing solar, a battery and a car →
The next step
Ask us the question the quote did not answer
Send us the quote you are looking at, or just the roof and the bill. We will tell you which of these words matter for your house, in writing, with the reasons.
- Call 01243 882444
- Email hello@solar-squirrel.co.uk
- Based Washington, West Sussex
If solar genuinely won’t pay for itself on your usage, we’ll say so and save us both an afternoon.
Rather see the numbers before you speak to anybody? Put your own bill on the house — it works out the size, the saving and the payback while you watch, and brings them down to this form with you.