TBE DesignerFree toolAuthorised Victron Energy Installer
Victron system designer
In short: our free designer plans a whole Victron system for a campervan, motorhome or off-grid cabin, from the battery and solar to every cable and fuse, and shows its working. It is a design aid: the 230 V side must be installed, tested and certified to BS 7671. Checked by Tom Alderdice, qualified electrician.
Designer v1.9.6Working shown
- Built from
- Victron datasheets and manuals
- Checked against
- BS 7671:2018+A4:2026 (Amendment 4)
- Informed by
- Anonymised data from 180+ monitored installations
- Last checked
A whole Victron system for your campervan, motorhome or off-grid cabin, with every cable and fuse sized by our cable size calculator.
How it works
- Energy first. Watts × hours for every appliance, plus the inverter/charger left on all day.
- Battery. Enough lithium for the days you want without any charging, using 90 % of its capacity.
- Solar. Sized on UK sun data for your region and the worst month you plan for, with the panels checked against the solar controller on a cold morning.
- Every circuit. Cable, fuse and lugs from the same engine as our cable calculator, built around a Lynx Distributor with a metal consumer unit and double-pole RCBOs on the 230 V side.
A design aid, not a design
Check every rating against your own parts. The 230 V side must be installed, tested and certified by a qualified electrician to BS 7671. Want it done properly? We'll fit it for you, or book a free call.
What it runs: appliance power and daily use
These are the average figures our system designer uses for each appliance. Pick the ones you have in the designer and it adds them up, sizes the battery, inverter and solar, and shows its workings.
Swipe the table sideways to see every column.
| Appliance | Power (W) | Full-power hours a day | Wh a day | Ah a day at 12 V | Ah a day at 24 V | Ah a day at 48 V |
|---|---|---|---|---|---|---|
| 12 V things (straight off the battery) | ||||||
| Compressor fridge | 60 | 6 | 360 | 30 | 15 | 7.5 |
| LED lights (6 lights, 3 W each) estimate | 18 | 4 | 72 | 6.0 | 3.0 | 1.5 |
| Water pump | 54 | 0.25 | 14 | 1.1 | 0.6 | 0.3 |
| Diesel heater | 30 | 5.5 | 165 | 14 | 6.9 | 3.4 |
| Roof fan | 45 | 1.5 | 68 | 5.6 | 2.8 | 1.4 |
| Phones and tablets (2 people, 15 W each) estimate | 30 | 1.5 | 45 | 3.8 | 1.9 | 0.9 |
| 4G/5G router | 7 | 12 | 84 | 7.0 | 3.5 | 1.8 |
| TV (12 V) estimate | 40 | 2 | 80 | 6.7 | 3.3 | 1.7 |
| 230 V things (through the inverter) | ||||||
| Laptop (230 V) estimate | 65 | 2 | 130 | 12 | 6.0 | 3.0 |
| Kettle (low-watt) estimate | 1,200 | 0.15 | 180 | 17 | 8.3 | 4.2 |
| Induction hob | 1,800 | 0.5 | 900 | 83 | 42 | 21 |
| Microwave (800 W output) | 1,250 | 0.2 | 250 | 23 | 12 | 5.8 |
| Coffee machine (capsule) | 1,310 | 0.1 | 131 | 12 | 6.1 | 3.0 |
| Hair dryer (low-watt) | 1,200 | 0.1 | 120 | 11 | 5.6 | 2.8 |
| Air fryer | 1,550 | 0.3 | 465 | 43 | 22 | 11 |
| Power tool charging | 310 | 0.25 | 78 | 7.2 | 3.6 | 1.8 |
- Full-power hours are the hours at the rated power that give an average day. A fridge cycles on and off all day; 6 full-power hours is its average.
- 230 V rows: Wh a day is what the appliance uses. Ah a day includes 10% inverter losses, as the designer allows.
- Leaving the inverter/charger on adds its standby draw, from Victron's figures: Victron MultiPlus 12/2000/80, 9 W (216 Wh a day); Victron MultiPlus-II 12/3000/120-32, 13 W (312 Wh a day). Search mode cuts this.
- Same energy, fewer amps: Ah a day is Wh divided by the system voltage, so the same use reads as fewer Ah at 24 V or 48 V. We design 48 V systems with you on a call.
- Where the figures come from: makers' datasheets where one exists, otherwise figures from our customer calls. Rows marked estimate are our own estimate, with no single datasheet behind them. Your own appliances may use more or less.
System designer questions
How do I size a leisure battery for my van?
Take the watt hours you use a day and multiply by the days you want to go with no charging. Divide by the system voltage for amp hours: 1,200 Wh at 12 V is 100 Ah. The designer does this and leaves headroom. Our battery guide compares types.
How much solar do I need for a campervan?
Enough to cover your daily use in the months you travel, within your roof space. Most van roofs take 1,000 to 1,200 W at best. The designer uses PVGIS sun data for your region, so you see what solar covers each month, winter included. Our campervan solar guide goes further.
What size inverter do I need?
Size it on the biggest 230 V load you run at once, in continuous watts. A 1,800 W induction hob needs a MultiPlus-II 12/3000: 2,400 W continuous at 25 °C, less in a hot van. The designer adds loads you'd run together and picks the smallest fit. Our inverter guide explains more.
12 V, 24 V or 48 V: which is right?
Victron's guidance is 12 V up to a 3,000 VA inverter, 24 V up to 5,000 VA and 48 V above that. Higher voltage means lower current for the same power, so thinner cables and less voltage drop. Leave it on Auto and the designer chooses. We design 48 V systems with you.
Does the designer size cables and fuses?
Yes. Every circuit is sized for its current, length and route, then checked against the BS EN 1648-2 voltage drop limits for 12 V vehicle circuits. The main battery fuse is a Class T on the board, or an MRBF beside the terminal for a 12 V battery up to 200 Ah. Cable size calculator.
Can I use it for an off-grid cabin?
Yes: pick Cabin first. The designer sizes solar on the worst month of the season you choose, with panels facing south at 35°; December is the worst across our 50+ monitored off-grid cabins. It adds a background draw from that fleet and swaps hook-up for a mains or generator inlet. Off-grid power costs.
What hook-up supply does the plan allow for?
16 A. In vans and motorhomes we fuse the AC input at 16 A and run 2.5 mm² H07RN-F from the inlet to the inverter/charger AC-in, at every size. BS 7671 Table 721 pairs a 16 A hook-up with 2.5 mm² cable. Need more? PowerAssist tops up the supply from the battery.
Is the plan ready to install?
It's a design aid, not a signed-off design. You get the sizing, working and parts list; your wiring diagram follows within three days of checkout. The 230 V side must be installed, inspected and tested to BS 7671, including Section 721, and certified on an Electrical Installation Certificate. Book a free call.