The gas meter is the smallest visible part of a gas connection, and one of the last things fitted, but it drives decisions that run all the way back to the earliest design stage. Get the meter sizing or position wrong and the whole gas connection can fail to meet capacity, planning, or safety requirements.
This guide covers gas meter installations for new builds, commercial premises, and housing developments.
Meter Classes in the UK
UK gas meters are classified by maximum flow rate in m3/hr. The common classes are:
U6 (6 m3/hr). Standard domestic meter. Covers typical household demand of a combi boiler plus gas hob.
U16 (16 m3/hr). Larger domestic or small light-commercial, for example a house with a high-output system boiler or a small cafe.
U25 (25 m3/hr). Small commercial. Typical for small restaurants, convenience stores, and light industrial units.
U40 (40 m3/hr). Medium commercial. Common in mid-size restaurants, laundrettes, and small factory units.
U65 and U100 (65 and 100 m3/hr). Larger commercial and industrial.
Above U100, meters are typically rotary or turbine and are specified project-by-project.
The meter class must match the declared maximum load. Undersizing causes pressure loss and undersupply. Oversizing is wasteful and can cause poor accuracy at low flow rates.
Positioning
Meter position is regulated by IGEM/G/5 and by the gas emergency rules that apply to all meter installations.
On domestic properties, the meter should ideally be in an external meter box on the front of the property. Internal meters are permitted but require ventilation and emergency access arrangements.
On commercial and industrial properties, the meter must be accessible to the emergency service without entering secure or occupied spaces. A dedicated meter housing or boundary kiosk is standard for anything larger than U25.
Minimum clearances must be maintained around the meter. Gas meters must not be installed above electrical equipment, in sleeping areas, or in unventilated enclosures. They must be accessible for reading and maintenance.
Meter Housings and Kiosks
For larger commercial meters, a dedicated meter housing kiosk is usually required. The kiosk contains the regulator, the meter, and any associated pressure test points. It is sited at the property boundary with GDN-approved access.
Kiosks need to be specified alongside the connection design. Their size affects the site layout, and their foundations affect the civils programme. Specifying them early avoids late-stage design changes.
Registration and Supply
A newly installed meter is registered to the property via a Meter Point Reference Number (MPRN). The MPRN is what retail gas suppliers use to set up the supply contract.
Registration is handled by the meter operator, but the occupier or developer needs to provide it to the chosen retail supplier to activate the contract. Without this step, the meter is live but not billable, and the supply may be cut off during routine reconciliation.
Smart Meters on Commercial Connections
Smart meter rollout started with domestic meters and has expanded to small and medium commercial. Most U6 and U16 installations are now SMETS2 smart meters. U25 and above are transitioning.
Smart meters provide half-hourly consumption data, which is useful for energy management. For commercial sites with high consumption or demand-response ambitions, specifying smart from day one avoids a later meter exchange.
Commissioning
Meter commissioning involves a tightness test across the installation, a purge to remove air from the pipework, and a let-by test at the meter regulator. Once all three are signed off, the meter is live.
Commissioning is usually the last step in the gas connection process, and it can only happen once the downstream installation (pipework to appliances) has been completed by the building contractor and is ready to be pressurised.
Common Pitfalls
Three problems come up repeatedly on new build gas meter installations.
First, meter position changes late in the build. The connection was designed for one position, but the architect or builder has moved the boiler to a different wall. This forces a design variation and, in the worst case, re-excavation.
Second, load changes without meter re-specification. A kitchen design is upgraded, a new appliance is added, but the meter and regulator are sized for the original load. The result is pressure drop and poor appliance performance.
Third, delayed retail supplier registration. The meter is installed and commissioned, but the occupier has not registered with a supplier. They turn up on day one expecting gas, and there is no contract in place. On housing developments, this often hits multiple plots at once if the developer has not set up a standing registration process.
How to Run a Smooth Meter Installation
Lock the meter position and load at the design stage.
If the load or position changes during construction, notify the connection provider immediately so the design can be updated before civils.
Coordinate the commissioning date with the building contractor so downstream pipework is ready.
Register with a retail supplier as soon as the MPRN is issued.
Keep the meter accessible during and after installation. Items such as sheds, fences, or bin stores can block meter access and create compliance issues down the line.
The Bottom Line
Gas meter installations are the most regulated and most visible step of the connection process, but they are also the step with the least flexibility. Specify correctly, position correctly, and commission on a realistic programme timeline, and the meter quietly does its job for 20 years or more.