What runs? How long off-grid? How it charges Cables and fuses Shopping list
Tap what you will have Tap a tile to add it, tap again to take it out. Open a tile to change the watts, the hours a day and how many. Items marked 230 V run through the inverter.
Daily use, winter
Daily use, summer
Inverter standing by
Peak 230 V together
Peak 12 V together Advanced: season (winter = October to March), "not at the same time" for 230 V loads that never run together, and the surge a motor pulls on starting. Inverter standby counts all day whenever any 230 V load exists.
Solar Panels on the roof
Where you will mostly be Scotland, north Scotland, south North of England Wales Midlands South-east South-west Northern Ireland
Panels
Controller
June, a day
December, a day How we got there Alternator (DC-DC charger) Charger None 18 A 20 A 30 A 40 A 50 A 60 A Driving a day
From driving, a day
Input from the starter battery How we got there Charger efficiency
A smart (Euro 6) alternator needs a DC-DC charger, not a split-charge relay; so does lithium.
Hook-up Mains charger None 10 A 15 A 20 A 30 A 40 A 50 A 60 A
Suggested
Refill from empty How we got there Hook-up days are not in the chart: it shows the van off-grid.
Month by month Month Solar Wh Driving Wh In Use Net Bank lasts
Every run One-way length of each run; the current comes from what it feeds. Cable sizes round up; the fuse protects the cable (fuse ≤ the cable's derated rating), the main fuse as close to the battery as possible. Negatives are sized the same as their positives.
Cable ratings: BS 7671:2018 Table 4D1A, column 4: reference method B (enclosed in conduit on a wall or in trunking), 2 cables single-phase a.c. or d.c., 70 °C thermoplastic, 30 °C ambient, derated for grouping (80 %, Table 4C1, two circuits bunched); voltage drop from Table 4D1B column 2 (2 cables d.c., mV/A/m). Source: Eland Cables, 'BS7671 Wiring Regs Table 4D1A and 4D1B' (reproduced from BS 7671:2018 Wiring Regulations) , retrieved 2026-10-29. Deliberately conservative: a van's cables run bunched through warm voids, and method B with that factor sits at or below method A (enclosed in a thermally insulating wall).
Grouping derating Main fuse class
Class T MEGA ANL MRBF
Check the fuse's interrupt rating against your battery's short-circuit current on its datasheet.
Class T is the default for lithium: its interrupt rating covers a lithium bank's short-circuit current.
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Before you build Every fuse here is at or below its cable's rating, and the main fuse goes as close to the battery as possible. A maker's manual overrides this page: fit the fuse it asks for, on a cable rated for it. Lithium: a BMS, charging cut off below 0 °C, the battery strapped down and fused at the terminal. 230 V (inverter output, hook-up inlet, RCD, consumer unit, sockets): done or certified by a qualified electrician. Nothing on this page tells you how to wire 230 V. Gas is not on this page. When it comes it will be planning only (use, bottle size, alarms), with a Gas Safe engineer for the installation. This is a planning guide, not a substitute for a qualified installer. Sizes are rounded the safe way; check every figure against the parts you actually buy. The link carries the whole plan with the van design; nothing is stored here. Solar yields: PVGIS (EU JRC), fetched 2026-10-29, flat panel, PVGIS-SARAH3.
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