Free Victron design tools, built the way we build systems
Two free tools from Tiny Build Electrics. We built them ourselves from Victron's datasheets and manuals and checked them against BS 7671, the IET Wiring Regulations. Each one shows its working and names its sources, so you can check every step.
TBE Designer
Plan a whole Victron system
For campervans, motorhomes and off-grid cabins. Tap what you'll run and how you'll charge, one question at a time.
Battery, MultiPlus, solar, alternator charging and hook-up
Every cable and fuse sized by TBE Cable Check
A wiring diagram, a parts list and the working behind it
Cabin plans compared with what real cabins we monitor need
Built from
Victron datasheets and manuals
Checked against BS 7671:2018+A4:2026 (Amendment 4)
Informed by anonymised data from 180+ monitored installations
Replacing a generator? Pick the kind of unit you let and see what solar and a battery would save on it each year, worked on 19 years of Cumbrian sun data.
You answer a few questions. What you'll run, where it's going and how you'll charge.
We size it against the makers' figures. Ratings come from Victron's datasheets and manuals, and the battery maker's for the battery. Cabin plans are then compared with what the cabins we monitor really use.
You see the working. Each answer lists the steps it took and the document behind each one.
From the cabins we monitor
We monitor 50+ off-grid cabins remotely. Their anonymised figures are how we check the designer's cabin plans against real life.
1.12 to 1.49kWh a dayWhat the middle half of cabins needed in summer (energy supplied per day; 34 cabins, May to August, 2024 to 2026).
99.5% solarShare of their energy that came from the sun from 27 April to 24 October 2026 (43 cabins reporting).
89% solarLast winter (November 2025 to February 2026), 14 of the 37 cabins reporting needed a generator or other top-up. That's why TBE Designer sizes winter solar on December sun.
Anonymised remote monitoring data, January 2024 to 24 October 2026. Totals and medians only: no names, places or system IDs.
Checked by Tom
Checked by Tom
Tom Alderdice founded Tiny Build Electrics and checked the rules and sources these tools work from. Your answer is worked out by the tool from what you enter. If you'd like a person to go through it, book a call and Tom will look at your plan with you.
Tom's qualifications
EAL Level 3 Award in the Requirements for Electrical Installations BS 7671:2018
EAL Level 3 Initial Verification & Certification of Electrical Installations
EAL Level 2 Fundamental Inspection, Testing and Initial Verification
NCC Test & Inspection, Electrical Maintenance of Touring Caravans & Motorhomes
NCC Extra Low Voltage Systems, Circuits & Equipment in Touring Caravans & Motorhomes
NCC Electrical Manufacturers Advanced Level, EIC
Plus 10 Victron Energy training courses since 2020, listed on our About page.
Tiny Build Electrics: Authorised Victron Energy Installer
BS 7671 is published by the IET and BSI and is their copyright. Our tools cite it; they don't reproduce it. Fleet figures are anonymised and only ever shown as totals or averages across cabins.
These are design aids, not a design or a certificate. Check every rating against your own parts, and have the 230 V side installed, tested and certified by a qualified electrician to BS 7671.
We use essential cookies to run the site and shop. With your permission we also use analytics and marketing cookies (Google and Meta) to improve the site and our ads. You can change your choice at any time.
Functional
Always active
The technical storage or access is strictly necessary for the legitimate purpose of enabling the use of a specific service explicitly requested by the subscriber or user, or for the sole purpose of carrying out the transmission of a communication over an electronic communications network.
Preferences
The technical storage or access is necessary for the legitimate purpose of storing preferences that are not requested by the subscriber or user.
Statistics
The technical storage or access that is used exclusively for statistical purposes.The technical storage or access that is used exclusively for anonymous statistical purposes. Without a subpoena, voluntary compliance on the part of your Internet Service Provider, or additional records from a third party, information stored or retrieved for this purpose alone cannot usually be used to identify you.
Marketing
The technical storage or access is required to create user profiles to send advertising, or to track the user on a website or across several websites for similar marketing purposes.
Tiny Build Electrics: Authorised Victron Energy Installer