Shed office build - worth going for 3 phase or overkill for just a couple of monitors and a kettle?

For a shed office setup, 3 phase is almost certainly overkill unless you're planning to run industrial equipment down the line. Single phase will handle monitors, a kettle, laptop chargers, and general office kit without breaking a sweat.

That said, I'd think carefully about how you're powering it before worrying about phases. If you're anywhere near the shed with decent roof exposure, a small solar setup with a Victron inverter/charger and a decent lithium bank (Fogstar do good value cells) could mean you're barely touching the grid at all for most of the year. That's the route I went with my motorhome setup and the principles translate well to a garden office.

If you do want a grid connection though:

• A decent 32A single phase feed will be more than enough
• Get a sparky to sign it off properly — garden offices can get complicated with Part P
• Factor in an RCD/consumer unit regardless

The kettle is probably your biggest draw at ~3kW, everything else is trivial by comparison. 3 phase starts making sense when you're talking about EV chargers, CNC machines, or serious workshop tools.

What's the rough square footage of the office? And are you thinking fully off-grid, hybrid, or just a straightforward grid spur? Makes a difference to what people would suggest.

@OldSailor78 pretty much nailed it. 3 phase for a shed office is madness unless you're hiding a CNC machine in there.

Single phase with a decent Victron inverter and some solar panels will handle everything you've listed no problem. I run my whole setup off a 5kWh Fogstar battery bank and a couple of panels — kettle, monitors, the lot.

Only caveat: if you're thinking EV charging down the line, plan the cable runs now even if you don't install the charger yet. Retrofitting conduit through walls is a pain. A 32A single phase feed covers most home EV chargers anyway, so still no need for 3 phase.

Keep it simple.

Agree with the above. Single phase, done properly, will be absolutely fine.

What actually matters for a shed office is the cable run distance from your consumer unit. Long runs = voltage drop, and people consistently undersize their cable for this. Calculate it properly or you'll end up with a kettle that barely boils and equipment running at the wrong voltage.

For off-grid specifically — and I'm guessing some of you are considering that route given the forum — a decent Victron inverter on single phase will handle everything you've listed without breaking a sweat. My setup runs a full workstation, monitors, and ancillaries no problem.

3 phase would just give you an unnecessarily expensive install, a more complex inverter requirement, and headaches you don't need. Unless @HarbourHermit's CNC machine comment was less of a joke than it sounded.

Totally agree with the consensus here. One thing worth adding — if you're even slightly tempted to go off-grid or add a battery backup (very worthwhile for a shed office that loses mains during outages), single phase plays far more nicely with inverter/charger combos like the Victron MultiPlus.

Running a proper off-grid or hybrid setup on a boat taught me that 3-phase inverters are a different beast entirely — significantly more expensive and complex for absolutely no gain in a domestic/light commercial context.

For your load list — monitors, kettle, laptop chargers — you're looking at maybe 2-3kW peak. A 32A single-phase feed is genuinely more than you'll ever need, and leaves plenty of headroom if you later bolt on a small solar array via a Victron SmartSolar MPPT.

Keep it simple and scalable. Single phase all day long.

Solid consensus here already. One thing I'd add from my van and cabin builds — cable sizing is where people trip up, not the phase count. Even for a modest shed office, if you're trenching cable from the house, factor in voltage drop over that run. A 2.5mm² cable that looks fine on paper can let you down over 20–30 metres once you're pulling kettle loads simultaneously with everything else.

Run 4mm² from the outset and thank yourself later. Cost difference in cable is minimal compared to re-digging a trench.

Also worth putting a small consumer unit in the shed itself rather than just a single socket — gives you proper circuit protection per circuit and room to expand. A 4-way unit from Screwfix is pennies relative to the job.