Temporary builder's supply
Site power and water, ready before the build starts
Temporary electricity and water for welfare cabins, tools, mixers and site offices. We apply to the network operator and water company, tell your electrician what has to be in place, and plan the supply so it can become the permanent one where possible.
A temporary supply is a real connection, not a formality
Generators and bowsers get a site started, but they are noisy, costly to run and need refuelling and refilling. Most builders want mains power and water on site as early as they can. That means an application to the electricity network operator and to the water company, just like a permanent supply.
The network operator treats a temporary builder's supply as a new connection. It needs a site plan, a load figure and a position for the supply. It is then quoted and programmed like any other job. If you leave it until the groundworks start, the site can run on generators for months.
We start the temporary applications as soon as you have a site layout, alongside the permanent ones. Planned together, the temporary supply can often be placed where the permanent one will go, which saves a second set of works later.
A temporary supply usually runs
- Welfare cabins, drying rooms and site offices
- Power tools, mixers and small plant
- Site lighting and security
- Temporary heating and drying out
- Hoists and larger plant on bigger sites
- Water for welfare, mixing and wheel washing
- Demolish-and-rebuild projects on an existing plot
Small or large temporary supply: which do you need?
Network operators split temporary building supplies by size. The size decides what the operator has to build, and so the price and the lead time.
| Small temporary supply | Large temporary supply | |
|---|---|---|
| Size UK Power Networks' split | Up to 69 kVA | Over 70 kVA |
| Typical sites | Self-builds, extensions, demolish-and-rebuild on a single plot, small developments. | Larger developments, commercial builds, sites with several cabins, hoists or tower cranes. |
| What is usually involved | A service cable from the nearest low-voltage network to a site cabinet or meter position. | A bigger cable, three-phase supply and sometimes new network equipment, such as a substation. |
| What to plan for | Where the cabinet goes, and whether it can stay as the permanent position. | The total site load, how long it is needed and how it fits with the permanent network design. |
Each network operator sets its own bands and process. The figures above are UK Power Networks' split, shown as an example. We confirm your operator's rules when we apply.
The RCD, earth electrode and TT earthing explained
The network operator brings the supply to its cut-out. Everything after that is your responsibility, and the operator expects some of it to be in place before it connects.
RCD protection
You must provide a residual current device (RCD) on the site installation, to BS 7671, the wiring regulations. It cuts the power quickly if current leaks to earth, which matters on a wet, busy building site.
Earth electrode
You must also provide your own earth electrode, again to BS 7671. This is usually an earth rod driven into the ground near the site board, installed and tested by your electrician.
TT earthing
Temporary building supplies are usually TT earthing systems. That means the site relies on its own earth electrode, not an earth provided by the network operator, which is why the RCD and electrode are needed.
Have your electrician ready before the connection date
The site board, RCD and earth electrode should be installed and tested by a qualified electrician before the operator arrives. If they are not ready, the visit can be wasted and the new date may be weeks away. We give your electrician the operator's requirements as soon as the offer is accepted.
You also need an energy supplier for a temporary supply, so that a meter can be fitted and the electricity billed. We tell you when to arrange it so the meter isn't the thing holding you up.
Building water and standpipes
Water for welfare, mixing and cleaning has to come through a supply the water company has agreed to. Each company has its own options and charges.
On many sites the simplest route is to apply for the permanent water service early and use it as the building supply once it is laid and metered. Where that isn't possible, the water company may provide a separate temporary connection.
Some water companies also hire out metered standpipes for use on approved hydrants. Taking water from a fire hydrant without the water company's permission isn't allowed, and the water used on site is charged either way.
Any temporary pipework and fittings on site still have to meet the water fittings rules, including protection against water flowing back into the mains. We confirm the water company's requirements when we apply.
Permanent service, used early
Often the tidiest option, where the water company allows it.
Temporary connection
A separate metered supply, removed or converted later.
Metered standpipe
Hired from some water companies for approved hydrants only.
Fittings rules
Backflow protection on site pipework still applies.
Can the temporary supply become the permanent one?
Sometimes. It saves money and a second set of works, but it has to be planned from the first application.
Whether a temporary supply can be converted varies by network operator, by water company and by site. Some will let the temporary cable or service become the permanent one if it is in the right place and the right size. Others want the temporary supply removed and a new permanent service laid.
Decide before you apply
Once a temporary cabinet is in the wrong place, moving it is a new job with its own quote and lead time. Settle the permanent meter position first.
- 1
Fix the permanent position
We agree the permanent meter or cabinet position with you before the temporary application goes in.
- 2
Size for both stages
We look at the site load during the build and the permanent load once the building is finished, including heat pumps and EV charging.
- 3
Ask the operator
We ask whether the temporary supply can be converted, and what it would need. The answer goes into the application.
- 4
Build the position early
Your builder prepares the meter box, cabinet base or ducting to the operator's drawing, so the supply lands in its final place.
- 5
Switch over
When the building is ready, we arrange the change from builder's supply to permanent supply, including any meter change with your supplier.
How long does a temporary builder's supply take?
A temporary supply goes through the same process as a permanent one: application, quotation, acceptance and payment, then the works. The quotation times are set by the national Guaranteed Standards of Performance, which all network operators follow.
A simple supply from a nearby low-voltage cable is usually the quickest. As an indication only, National Grid Electricity Distribution's pricing guide shows about 8 weeks from acceptance and payment for a single domestic connection. Every operator publishes its own figures, and larger supplies take longer.
Allow more time if any of these apply:
- The supply has to cross or dig up a public road, which needs highway permits.
- Cables cross land you don't own, which needs a wayleave.
- The local network is full and needs a new substation or reinforcement.
- Your side of the installation isn't ready on the day.
Information for a temporary supply
- Site address and a location plan
- Where you want the temporary supply, marked on a plan
- What it will run: cabins, tools, heaters, hoists or cranes
- Single-phase or three-phase, if you know
- When you need it and for how long
- The permanent meter position, if it is decided
- Details of any existing supply on the plot
Send what you have. We'll work out the load with you if you don't have a figure. Our fee is fixed and agreed before we start.
How long connections takeTemporary supply questions
What is a temporary builder's supply?
It is a temporary electricity or water connection that powers a building site before the permanent supply is in. It runs cabins, tools, lighting and welfare facilities during the build.
Do I need my own RCD and earth electrode?
Yes. For a temporary electricity supply you provide an RCD and an earth electrode to BS 7671. These supplies are usually TT earthing systems, so the site relies on its own earth rather than one from the network operator.
What does TT earthing mean on a building site?
It means your installation is earthed through its own earth electrode in the ground, not through the network operator's cable. An RCD is used so that a fault cuts the power quickly.
Can my temporary supply become the permanent supply?
Sometimes. It varies by network operator, water company and site. If you plan the permanent position before applying, the temporary supply can often be placed there and converted later.
How big a temporary supply do I need?
It depends on what will run at the same time. A single plot with cabins and tools usually needs a small supply. Hoists, cranes and several cabins can push you into a large or three-phase supply. We work the load out with you.
Can I use a fire hydrant for building water?
Not without the water company's permission. Some water companies hire out metered standpipes for approved hydrants. Often the better option is to get the permanent water service in early and use it during the build.
Do I need an energy supplier for a temporary supply?
Yes. The network operator provides the connection, but a supplier has to fit a meter and bill for the electricity. We tell you when to arrange it.
Need power and water on site?
Tell us where the site is and what the supply will run. We'll confirm the operator, the route and a clear quote for managing the application.