What Is a Meter Isolator Switch – And When Do You Need One?
A meter isolator switch provides a means of isolating the customer's installation on the load side of the electricity meter. It allows work such as a consumer-unit change to be carried out without repeatedly removing the distributor's cut-out fuse.
Quick answer: A meter isolator is normally installed after the electricity meter and before the consumer unit. When authorised and correctly operated, it disconnects the customer-side installation while leaving the metering equipment energised upstream.
Ownership and permission vary. The supplier, meter operator or distribution network operator may control who can install, seal or operate equipment at the intake position.
Browse meter isolation and changeover switches or compare main switches and rotary isolators.
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What Does a Meter Isolator Switch Do?
Its job is straightforward: provide a switching and isolation point between the metering equipment and the consumer installation. The device should disconnect the conductors required for the supply arrangement and be correctly rated for its duty.
It is not an overcurrent protective device and does not replace the service cut-out fuse, RCDs, RCBOs or the consumer unit's main switch.
Where Is a Meter Isolator Installed?
The typical sequence is:
| Order | Equipment | Purpose |
|---|---|---|
| 1 | Distributor's service head and cut-out | Service connection and supply protection |
| 2 | Electricity meter | Energy measurement |
| 3 | Meter isolator | Customer-side isolation point |
| 4 | Consumer unit or distribution board | Main switching and circuit protection |
The physical arrangement must respect meter tails, enclosure space, sealing, access and the requirements of the relevant organisations. Do not assume that space inside a meter cabinet gives permission to install there.
When Do You Need a Meter Isolator?
A meter isolator is especially useful for consumer-unit replacements, intake alterations and future maintenance. It gives an authorised electrician a defined isolation point without needing the cut-out fuse removed each time.
Whether one is mandatory for a particular job depends on the existing intake, supplier or network process and the scope of work. If no safe means of isolation is available, arrange the correct attendance rather than interfering with sealed equipment.
Why Are 100A Meter Isolators Common?
Many UK single-phase domestic supplies use service equipment and meter tails associated with a maximum 100A arrangement, so 100A double-pole isolators are widely used. That does not mean every property has a 100A cut-out fuse or that a 100A device automatically suits every installation.
Confirm the supply capacity, conductor size, terminal capacity, prospective fault current, enclosure and manufacturer data. For three-phase supplies, a suitable four-pole arrangement may be required.
Options include the 100A Plastic Meter Isolator and the metal meter isolation unit.
Who Can Install or Operate a Meter Isolator?
Responsibility at the intake can be split between the network operator, energy supplier, meter operator and customer. Seals and the cut-out must not be disturbed without authority. In many cases, the supplier or meter operator arranges the isolator or authorises the work.
Before attending: Establish who owns the equipment, who can remove seals, and whether an isolation appointment is required. Local processes vary even when the hardware looks identical.
Meter Isolator vs Consumer Unit Main Switch
| Device | Position | Primary Job |
|---|---|---|
| Meter isolator | Between meter and consumer unit | Isolate the customer installation from the metered supply |
| Consumer-unit main switch | Inside the consumer unit | Isolate the board and its outgoing circuits |
| Rotary isolator | Usually local to equipment | Provide local isolation/switching for a specific load |
Meter Isolator FAQs
Does a smart meter include an isolator?
Do not assume it does. A meter may have internal switching for metering functions without providing an installer-operable isolation device.
Can an electrician pull the service fuse?
Only where the relevant authority and procedure permit it. Sealed network or metering equipment must not be interfered with.
Is a meter isolator the same as the main switch?
No. They may both isolate an installation, but they occupy different positions and serve different operational purposes.
Do three-phase supplies need a four-pole meter isolator?
The required poles depend on the supply and isolation design. Confirm the specific arrangement rather than selecting by phase count alone.
Final Word
A meter isolator is a practical customer-side isolation point between the meter and consumer unit. Select it for the actual supply and arrange the work through the organisation responsible for the intake equipment.
Need an intake isolation option? Browse meter isolation and changeover switches.
Compare the 100A plastic and metal-enclosed options.