Power to Your Garage or Shed: A Rotherham Electrician’s Honest Guide

You’ve got a garage or a shed at the bottom of the garden, and it’s dark, cold and a bit useless once the evenings draw in. You want a couple of lights, a few sockets, maybe somewhere to plug the freezer in or run the tools. Nothing fancy.

That’s one of the most common jobs I get asked about as an electrician in Rotherham. It’s also one where I see a lot of dodgy setups that people have lived with for years without realising how risky they are.

So here’s the plain English version.

Quick answer

To get power to a garage or shed safely, you’ll normally need a new dedicated circuit from your house, run in armoured cable (usually called SWA) that’s buried or fixed properly, with RCD protection and a small consumer unit in the outbuilding. A new circuit like this is notifiable under Part P in England, so it should be done by a registered electrician who can certify it. Every job is quoted properly after we’ve had a look.

This is about the everyday garage and shed

This post is for the bloke (or anyone else) who just wants a working garage or shed. Lights so you can find things, sockets for a drill or a battery charger, and somewhere to plug in the spare freezer.

If you’re planning a proper insulated garden office with heating, data and a desk you’ll sit at all day, that’s the bigger version of this job. Have a look at our garden office electrics content for that. A lot of the principles are the same, it’s just more of everything.

Why the extension lead through the window has to go

I see this all the time across Rotherham, Maltby and Bramley.

A common call I get starts with “we’ve had an extension lead running out to the shed for years and it’s been fine”. Then something trips, or the lead gets chewed by the mower, and suddenly it isn’t fine.

The usual bodges

• An extension lead fed through a window or under the back door, left there permanently
• A length of flex clipped along the fence to the shed
• A cable reel left half wound on the garage floor running a heater
• Indoor extension leads daisy chained together to reach the end of the garden

Why they’re dangerous

These leads aren’t built to live outdoors. Sunlight, frost and damp break the outer sheath down over time, and there’s nothing to stop a spade, strimmer or hedge trimmer going straight through them.

A cable clipped to a fence is at the mercy of the fence. Panels blow down and posts rot.

Cable reels left partly wound can overheat when you run something like a heater off them. Electrical Safety First have some sensible garden electrical safety advice on leads and RCDs that’s well worth a read.

How a proper garage or shed supply is done

Armoured cable (SWA)

The cable we normally use to feed an outbuilding is steel wire armoured, which everyone in the trade calls SWA. It has a layer of steel wires wrapped around the inner cores, with a tough outer sheath on top.

The armour protects it, so it can be buried or run outside where ordinary twin and earth cable has no business being.

Buried depth and routing

When SWA goes underground, it needs to be deep enough to stay clear of normal gardening. The depth depends on the ground and what’s going over the top, such as a lawn, a border or a path, so I’ll look at your garden before deciding.

A few general points on routing:

• Warning tape is usually laid above the cable so anyone digging later knows it’s there
• We plan the route to avoid where you’re likely to put fence posts, trees or a new patio
• Sometimes the cable can be clipped along a wall at height instead, if the route suits
• Where it rises out of the ground and enters the building, it’s protected and glanded properly

A small consumer unit in the outbuilding

At the garage or shed end, we’d normally fit a small garage consumer unit. This is a compact fuse board that splits the incoming supply into its own circuits, typically one for lights and one for sockets.

You can switch the outbuilding off locally, and a fault on the sockets doesn’t leave you in the dark.

RCD protection

An RCD watches for current leaking to earth, which is what happens when someone touches something live, and it cuts the power very quickly.

The wiring regulations expect electricians to provide 30mA RCD protection for socket circuits like these. How and where it’s fitted depends on your existing board. If your house board is old, that’s a conversation worth having too, and our consumer unit upgrades page explains more.

For a deeper dive, see our post on RCD, RCBO, AFDD and surge protection explained.

Earthing for detached outbuildings, explained simply

This one genuinely needs a judgement on site.

Earthing is what gives fault current a safe path so the protective devices can do their job. In a detached garage or shed, there are two broad ways of handling it.

Option one: extending the earth from the house

In some cases the house earth can be carried out to the outbuilding through the SWA cable. That can be the right answer, but it depends on what type of supply you’ve got and what’s in and around the outbuilding.

Option two: a separate earth at the outbuilding (TT)

In other cases the outbuilding is better set up with its own earth electrode, an earth rod driven into the ground. This is called a TT arrangement, and it relies on RCD protection to work properly.

Why I won’t decide it over the phone

Many homes in South Yorkshire have a supply type (often called PME) where extending the house earth outdoors needs careful thought. Things like metal pipes, a metal framed building or an outside tap nearby all come into it.

So which option you get is decided by the electrician after looking at your supply and the building. Our post on earthing and bonding explained goes into this a bit more.

What power do you actually need?

People often under or over estimate this.

Light use

• LED lights
• A few double sockets
• Phone or battery tool chargers
• A radio

A modest cable will usually do it.

Medium use

• A chest freezer or fridge
• Power tools like a mitre saw or grinder
• A compressor
• A small heater now and then

Still fine for most setups, but I’ll want to size the cable with some headroom.

Heavy use

• A welder
• An oil filled or fan heater running for hours
• A lathe or bigger workshop kit
• Maybe charging a car later on

This is where cable size and the length of the run really matter. A long run to the bottom of a big garden in Wickersley loses more voltage than a short hop to a garage beside the house, so the cable has to be chosen for both.

If there’s any chance you’ll get a welder or an EV charger in future, tell me now. It’s far cheaper to fit the right cable once than dig the garden up twice. If a car charger is on the cards, have a look at our EV charger installation page as well.

Attached garage or detached garage?

These are quite different jobs.

Attached or integral garage

If the garage is part of the house, there’s often no need for buried cable. We can usually run a circuit through the house to it, and sometimes the garage can be fed straight from your main board.

Integral garages are common in newer estates around Rotherham and Doncaster, and they’re usually the simpler and cheaper option.

Detached garage, shed or workshop

Anything standing on its own needs the cable to get across the garden somehow, which is where SWA, the route and the earthing decision all come in. Older terraces and semis in Barnsley and Sheffield often have the garage at the end of a long yard, so the run can be longer than people expect.

Is it notifiable under Part P?

Yes, in most cases. In England, installing a new circuit in a home is notifiable building work under Part P, and that includes circuits feeding a garage, shed or other outbuilding in the garden. The Approved Document P guidance on GOV.UK sets this out.

As a NAPIT registered electrician, we can certify our own work. You get an Electrical Installation Certificate, and the job gets notified to building control for you, so you receive a Building Regulations compliance certificate afterwards.

Frequently asked questions

Can I just use an outdoor extension lead for my shed?

For occasional use, like the odd bit of hedge cutting with a plug in RCD, an outdoor rated lead is fine. As a permanent supply to a shed or garage, it isn’t a safe setup.

Do I need a consumer unit in my garage?

For a detached outbuilding with lights and sockets, a small garage consumer unit is the usual approach. It gives local switching and separate protection for each circuit.

How deep does the armoured cable need to go?

Deep enough to stay clear of normal digging, and it depends on the ground and what goes over it. I’ll assess this on site and use warning tape above the cable.

Can I run a welder in my garage?

Often, yes, but the cable and supply need choosing with that in mind from the start.

How much does it cost?

Every job is quoted properly after we’ve had a look, because the cable run, the ground and what you want to power all vary. It’s free to ask.

Related services and guides

• Outdoor electrical work
• Garden office electrics
• EV charger installation
• Earthing and bonding explained
• RCD, RCBO, AFDD and surge protection explained
• Hot tub electrics: what to sort before it arrives

Contact MP Electrical

If you need help with power to your garage or shed, or any electrical work in Rotherham or South Yorkshire, MP Electrical are happy to help.

📞 Call our office on 01709 645115

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