Commercial buildings can contain a mixture of electrical supplies, plant, tenant spaces and individual loads. When more detailed electricity measurement is needed, one of the first questions is whether the area being monitored uses a single phase or three phase supply.
Single phase and 3 phase sub meters perform the same basic job: they measure electricity consumption for a defined part of an electrical system. The difference is the type of supply they are designed to measure.
For commercial property managers, facilities teams and energy managers, getting this distinction right is an important part of specifying useful metering. It helps ensure that the meter suits the electrical arrangement and that the consumption data relates to the area or equipment you actually want to monitor.
What is single phase metering?
Single phase metering measures electricity consumption on a single phase electrical supply.
Single phase supplies are commonly associated with smaller electrical loads. Within a commercial building, they may serve individual rooms, smaller tenant units, lighting circuits, office areas or other loads where three phase power is not required.
A single phase meter records the electrical energy passing through that supply. Where it is installed as part of a wider metering system, the data can provide a more detailed picture of consumption than the building’s main electricity meter alone.
This can be useful when a facilities or property team wants to separate one area from another rather than reviewing only whole-building consumption.
The presence of a single phase supply does not automatically mean it needs its own meter. The decision should be based on whether measuring that supply will provide useful information.
For example, separately monitoring a small tenant area may be useful for cost allocation or property reporting. Measuring another minor circuit may add little value if nobody will use the resulting data.
That is why meter selection should follow the measurement requirement, rather than the other way round.
What is three phase metering?
Three phase metering measures electricity consumption across a three phase electrical supply.
Three phase supplies are widely used in commercial and industrial environments because they can support larger electrical loads and equipment. Within a commercial property, three phase power may be associated with major plant, mechanical services, larger occupied spaces, distribution boards or other substantial loads.
A 3 phase sub meter can provide a separate record of the electricity used by one of these areas or systems.
This can help a property team answer questions that a main utility meter cannot. For example, the team may want to see how much electricity a particular plant area is using, compare different parts of a building or investigate why consumption has changed.
The meter still needs to be selected and configured around the electrical system it is measuring. Three phase metering is therefore not simply a larger version of single phase metering. The electrical arrangement, current levels, meter type and intended data collection method all need to be considered.
Single phase vs three phase: what is the practical difference?
The practical difference is the electrical supply being measured.
A single phase meter is intended for a single phase circuit or supply. A three phase meter is designed to measure a three phase supply.
For a commercial property team, the decision is normally determined by the building’s electrical distribution rather than personal preference.
A building might contain single phase tenant areas alongside three phase plant and distribution equipment. A larger estate could contain many different arrangements across several buildings.
This is why a site-wide approach to metering is often more useful than selecting meters individually.
Before specifying a meter, it helps to establish what the circuit supplies, whether it is single phase or three phase, how much detail is required and how the resulting data will be collected.
Where might single phase sub meters be used?
Single phase sub meters may be appropriate where smaller areas or loads need to be monitored separately.
Examples can include individual office areas, small commercial units, selected circuits or parts of a building that are already supplied independently.
The value comes from being able to separate that consumption from the rest of the site.
A landlord managing several occupied areas, for example, may want clearer information about electricity use within particular units. A facilities team might want to separate a specific building service from general consumption.
The electrical arrangement ultimately determines whether single phase metering is suitable.
For a wider explanation of how additional meters can be used across buildings, see Elcomponent’s electrical sub metering systems page.
Where might a 3 phase sub meter be used?
Three phase metering becomes relevant when the supply or equipment being measured operates on three phases.
In a commercial property, this can include plant rooms, larger distribution boards, mechanical equipment, larger tenant supplies or other significant electrical loads.
The purpose is not necessarily to measure every large piece of equipment. It is to identify the areas where separate consumption data will help the organisation manage the building.
For example, if overall electricity consumption rises, a whole-building meter may show the change but not explain where it occurred. Separately monitored three phase loads can provide more information for investigation.
This can be particularly useful in buildings where plant consumption represents a significant part of the total electrical load.
Direct metering and CT-operated metering
The way a meter measures a circuit also depends on the electrical current involved and the type of metering arrangement.
Some meters measure current directly. Other applications use current transformers, often shortened to CTs, to provide the current measurement required by the meter.
This is a separate consideration from whether the supply is single phase or three phase.
If you are looking for technical installation information relating to three phase sub meters and current transformers, Elcomponent has a dedicated submeter installation guide.
Keeping that technical subject separate from the initial metering decision helps ensure that the right meter is specified before installation details are considered.
How many meters does a commercial property need?
There is no single answer.
A useful metering system is based on the questions the property or energy team needs to answer.
Some buildings may benefit from only a small number of additional meters. Others may require more detailed measurement across tenants, plant, floors or separate buildings.
The starting point should therefore be the information requirement.
Ask what needs to be compared, investigated or reported. Then identify which parts of the electrical system correspond with those needs.
This approach helps avoid installing additional meters simply because measurement is possible.
Elcomponent’s metering and energy monitoring services include system design, site surveys, commissioning and system management, allowing the metering requirement to be considered as part of the wider site.
How will the meter readings be collected?
Another important question is what happens after the meter is installed.
If a member of staff needs to visit every meter and record a reading manually, the process can become difficult to manage across a large commercial property or multi-site estate.
Compatible meters can form part of a data collection system so readings can be brought together for analysis and reporting.
This creates a clearer route from individual meter measurements to useful property information.
Elcomponent’s MW2 energy monitoring software is designed to bring energy data into dashboards, reports and analytical tools where the wider monitoring system supports that approach.
The technology used should follow the property’s needs. Not every site requires the same level of data collection.
Why meter specification matters
Electricity metering is most useful when the meter, supply, communications and reporting requirement have been considered together.
Choosing between single phase and three phase metering is one part of that process.
A correctly selected meter still needs to measure a useful point within the electrical system. The data then needs to be available to the people responsible for the property.
This is particularly important for commercial sites where several stakeholders may need different information.
A property manager may focus on occupied areas and cost allocation, while an energy manager may focus on trends and unusual consumption. A facilities team may need information about plant and building services.
The metering arrangement should support those real operational needs.
For broader government information about metering in non-domestic premises, see the Department for Energy Security and Net Zero’s non-domestic smart metering guidance.
From individual meters to a wider monitoring system
Single phase and 3 phase sub meters can both form part of a wider approach to understanding electricity consumption.
The goal is not simply to produce more readings. It is to create useful information about how energy is being used across the building.
That may mean measuring tenant spaces, plant, separate buildings, individual departments or selected electrical loads.
Once the measurement requirement is clear, the appropriate meter type can be selected.
For property teams looking beyond individual meters, Elcomponent’s energy monitoring systems page explains how metering, data collection and monitoring software can work together.
Discuss your metering project
If you need additional electricity measurement across a commercial property or estate, Elcomponent can help assess the existing setup and identify a suitable metering approach.