PV Suite

Have the dimensions of every roof plane, the module you intend to specify, the dwelling ground floor area and — if you are going as far as the money — the quoted installed cost and the household electricity demand. The five steps share one set of arrays, so set the roof up first and everything downstream follows from it.

Project details and Site & basis sit in the toolbar and open as modals, so they stay out of the way. Your name and company are printed on the PDF and are needed before it can be produced. The SAP region sets the radiation from Table U3, and the basis — SAP 10.2, SAP 10.3 or HEM v1.0 — sets the fuel prices, the carbon factors and the storage model.

Requirement L3 of Approved Document L Volume 1, 2026 edition. A dwellinghouse is sized from its ground floor area under equation 5.1; a building containing dwellings from its footprint, which equation 5.2 takes as the gross internal area divided by the storeys. The benchmark is an array over 40% of that area at 0.22 kWp/m², facing south-east to south-west, pitched at 45 degrees and not overshaded. The chart compares it against everything the roof carries, stacked so each plane’s contribution is visible.

Every plane you switch on is drawn below, at one common scale, with a compass arrow above it showing which way it faces. Click a module to take it off, click bare roof to add one, or drag a module to another plane. Requirement L3 is assessed on the whole building, so every plane counts towards the total, and the generation, storage and cashflow all follow immediately.

Modules are spread evenly across the rows a plane can take, and each row is centred across the plane. Six on a two-row plane sit three and three rather than four and two; where the total does not divide, the odd ones go to the rows nearest the eaves, so five sits two over three. The grid of rows is centred up the slope, so the array sits centrally whether it is full or not.

Rows are independent. Clicking a module takes it off that row and recentres that row alone — nothing is pulled up or down from another row to fill the gap, so you can deliberately leave a row short. Clicking bare roof adds a module to the row you clicked in, or the nearest one with space. Dragging a module to another plane takes it from the row it was in and puts it in the row you drop it on. When you want the even arrangement back, Even rows re-spreads whatever is on each plane without changing any totals.

Max fit puts a module in every position on every plane. Add a module puts one on the best-yielding plane that still has room. Where you have a target — a quoted system size, or the number needed to reach the L3 benchmark — type it into Roof planes and press Allocate: the modules go to the best-oriented plane first and spill onto the next only when that one is full, because a module on a south plane is worth roughly half as much again as the same module facing north. You can also type a count straight into a plane’s Modules cell.

The dashed line is the usable area, and the small figures on each side are the edge offsets in millimetres. They default to Appendix B of Approved Document L 2026 — 600 mm from the ridge, 500 from an eaves, verge or parapet — and are all adjustable under Setbacks and gaps, alongside the other Appendix B figures: 750 mm from a party wall centre line, 300 from a vent or flue, 500 from a window or door, 1000 from an automatic opening vent and 2000 mm maintenance access to an unprotected roof edge. Approved Document B does not currently set numerical distances for panels; the Building Safety Regulator has proposed fire provisions for roofs with energy-generating installations, so check the position at the time of the work.

Because the array always sits as a centred block, an obstruction is handled by reducing the count on that plane, or by setting a larger edge offset on the side it sits, rather than by leaving a hole in the middle of the array. Slope length is measured up the pitch, not the horizontal projection: a plan dimension will undersize the array.

Every plane is laid whichever way round fits more modules, worked out for that plane on its own, so a wide plane and a tall one can come out differently. Where a plane has to be laid a particular way — a rail run, a sightline, matching an existing array — set its Layout column under Roof planes to Landscape or Portrait and it will be. The caption under each drawing says which way it is laid, and if forcing an orientation fits fewer modules than the other way round the tool says so and by how many. The Module dialog sets the starting point for every plane.

Most UK residential modules in 2026 are about 1.70 to 1.76 m by 1.13 m at 400 to 450 W, roughly 1.9 to 2.0 m² each, and the default is that mainstream 1722 × 1134 mm, 440 Wp size. The list holds the common size classes and there is a custom option; always take the actual dimensions from the datasheet for the module being specified.

Each plane goes through equation (M1) on its own orientation and tilt, and only the monthly outputs are summed. That matters: a north plane produces roughly a third less than a south plane of the same size, and adding the capacities then applying one orientation would flatter a split roof substantially. Where the starting point is a quoted system size rather than a roof, switch the array source to “entered directly” and you get the same table for arrays instead of planes.

Storage is off by default. With it off the split is whatever Appendix M1 step 3 gives without a battery, and the curve still shows what one would add, so the decision can be made on the numbers. Switch it on and enter usable capacity, not nameplate: a 10 kWh battery at 90% depth of discharge has 9 kWh usable. Step 3c caps the capacity used in its coefficients at 15 kWh, which is why the curve flattens and why the ceiling is drawn on the chart.

A cashflow on the split from the previous step. Prices default to SAP Table 12, which is an energy rating figure and will usually differ from a live tariff — enter your own where you have them. Degradation reduces generation each year, inflation raises the value of each kWh, and the inverter is replaced once in the year you give. Break-even is interpolated within the year, so it is not always a whole number.

Appendix M1 is a monthly energy rating method, not an hourly simulation, and not a yield guarantee. The storage model excludes round-trip efficiency, depth of discharge, control strategy, export limits, degradation and time-of-use tariffs — and a time-of-use or export-optimised tariff is often the main reason a battery pays in practice. Packing modules onto a roof is ordinary geometry: SAP has no procedure for it, and structural capacity, fixing, wind loading, string layout and inverter sizing are all outside this tool.

PDF contents in the toolbar decides which of the five steps the report carries. A planning submission may want the roof and the drawings and nothing else; a client may want the money. The cover, the headline result and the verification code are always printed, the step numbers close up around whatever is left, and the summary panel drops any figure belonging to a step you left out rather than quietly contradicting it. Leaving out Method and limitations is not advisable for anything sent to a third party.

With Roof drawings on, each plane is drawn to scale with its modules laid out on it, dimensioned in millimetres, with the edge zone hatched, the buildable area dashed and a compass showing the aspect. The scale is a standard one — 1:20, 1:50, 1:100 and so on — stated under every drawing, so it can be measured off the page. Planes share a scale where they are near enough in size to be compared; where they are not, each takes the largest scale it fits at. A plane that takes no modules is still drawn, because the drawing shows why.

The PDF needs your name and company. It shows the working for whichever steps you asked for, including a plane-by-plane roof table and a per-array generation table. Save inputs writes a .briarypv file that reopens the whole workspace. Outstanding inputs are listed on the right of whichever step they belong to, and each is a link that opens the modal holding the field and focuses it. For problems, email toolsuite@briary.co.uk with the browser and what you entered.