How to choose your distribution board size
Distribution board size is measured in modules -- the number of DIN-rail positions the devices take up. This page walks through the reasoning for reaching the right size, rather than handing you a fixed number. The exact module count is always calculated at the design stage, from your home's actual circuit list.
How to think about sizing
List your existing circuits
Each circuit -- lighting, sockets, kitchen, heat pump -- takes up its own space in the board. The first step is knowing how many you'll have.
Think about the future
An EV charger, solar panels, extra rooms, or a smart-home module -- if any of it might come later, it's worth accounting for now.
Add reserve modules
A board filled right to the edge at installation leaves no room for expansion later without a full replacement -- good practice is to plan reserve from the start.
Confirm the size with a specialist
The exact module count and enclosure size is calculated at the design stage from your home's specific circuit list -- not from a rough average.
What shapes the board's size
The DIN rail standard
Every device in a distribution board mounts on a 35 mm wide DIN rail (EN 60715) -- the module is the basic unit of that width used to measure board size.
The module as a unit
Each device -- MCB, RCBO, contactor -- takes up a set number of modules; the total sets the minimum required board width.
Your circuit list as the baseline
However many circuits your home has, that's the base module space you need -- lighting, sockets, and larger appliances are usually separate circuits.
Reserve for future needs
An extra circuit, a smart-home module, or EV charger protection fits far more easily into a board that isn't filled to the last slot.
Room for other devices
Sometimes the board also needs space for other protection devices, for example solar inverter protection -- worth knowing at the planning stage.
Precision comes from the project
The exact module count and enclosure size is precisely calculated at the design stage -- this page gives you the framework, not a fixed number.
What a consultation includes
Want to know what size would suit your specific home? We can talk it through one-on-one.
- Discussion of current and planned circuits
- A recommendation on reserve capacity
- Room planning for extra devices (EV, solar)
- A link to full design and installation services
- No sales pressure
Frequently asked questions
How many modules do I need?
It depends on your circuit count and planned expansions -- the exact figure is calculated at the design stage, not from a rough average.
Is a bigger board always better?
Not necessarily -- a sensible reserve matters more than maximum size; an oversized board can be needlessly expensive and space-consuming.
What if I'm planning solar panels later?
Worth mentioning it now while sizing the board, so there's room for inverter protection without a full replacement down the line.
Can I add a second board later?
That's a possible solution, but it's usually cheaper and simpler to plan reserve from the start than to add a second enclosure afterwards.
How is the exact board size calculated?
From your home's actual circuit list and any planned additional devices -- that's design work done together with an electrician or designer.
Not sure what size fits your home?
Book a consultation -- we'll talk through your circuit list and the reserve you need, no sales pressure.