Single-phase electricity supply

What a single-phase domestic connection provides and how to assess it for solar, storage, EV charging and heat pumps.

A single-phase supply provides one line conductor and neutral to the customer installation. It is the normal arrangement for a house and can support substantial electrification when the service, maximum demand and control strategy are suitable.

“Single-phase” does not mean “low power”, and “three-phase” is not automatically better. The design should start with the equipment’s actual electrical demand, the confirmed connection capacity and the DNO’s response.

Voltage and network arrangement

The public low-voltage network distributes three-phase electricity. A single-phase property is connected between one phase and neutral, while other properties are distributed across the phases.

As at 22 July 2026, the declared low-voltage supply under the Electricity Safety, Quality and Continuity Regulations remains 230 V, with a permitted variation of +10% and -6%. That is a range of 216.2 V to 253 V. Proposals to modernise the statutory range do not change the law until the regulations are amended.

The nominal voltage is used for the familiar capacity calculations. Actual appliance current and voltage can vary, so circuit and voltage-drop design uses the applicable standards and manufacturer data rather than the rounded headline figure alone.

Connection capacity

For a single-phase connection, approximate apparent power at nominal voltage is:

60 A: 13.8 kVA
80 A: 18.4 kVA
100 A: 23.0 kVA

These figures apply only when the fitted fuse rating is confirmed. The DNO may authorise a connection capacity on different terms, and the service cable or upstream network may prevent an uprating even where the cut-out body can accept a larger fuse.

The whole-property maximum demand must be assessed. A domestic installation can have circuit ratings whose sum is far higher than the service rating because justified diversity applies. A new sustained or deliberately scheduled load changes that assessment.

Identifying the phase arrangement

One fuse carrier and a single-phase meter usually indicate a single-phase service. Three carriers and a polyphase meter indicate three-phase. There are exceptions: a multiphase cut-out can feed only one live phase to a single-phase meter.

Do not remove covers or seals. Confirm the phase arrangement from the accessible equipment, meter details and DNO records. The number of spaces in a consumer unit says nothing about the number of supply phases.

EV charging and heat pumps

A typical nominal 7.4 kW single-phase charge point can draw 32 A for hours. That is a material part of a 60 A or 80 A connection. Dynamic load management can reduce the charge rate when the home approaches its confirmed import limit.

For a heat pump, use the manufacturer’s maximum electrical input and current, including start behaviour and every auxiliary source that can operate. The thermal output printed in the product name is not its electrical demand. Backup heaters, immersion elements and other heating controls can dominate the peak.

The ENA route current at this review date distinguishes straightforward connect-and-notify cases from those requiring an application. The installer should submit the whole-connection demand and service information through the current process rather than deciding from the head fuse alone.

Many homes can operate an EV charger and heat pump on single-phase with a suitable service and control design. Others need a load limit, fuse or service upgrade, or three-phase. Product type alone does not decide which.

Solar and battery storage

For generation, 16 A per phase is the key upper limit within the G98 definition for a Type Tested micro-generator installed on a single customer’s installation. At nominal 230 V, 16 A corresponds to 3.68 kW.

That is a connection-path threshold, not a universal single-phase export cap. A larger or aggregated system may be accepted on a single phase through G99, with or without an export limit under G100. The DNO decides from the proposed registered capacity, export, network and equipment evidence.

This distinction matters for batteries:

the inverter’s Registered Capacity affects the G98 or G99 assessment
a configured export limit can affect the agreed export but does not erase installed capacity
grid charging contributes to import maximum demand
backup operation and islanding need a separate installation design

Do not specify three-phase solely because a proposed inverter is above 3.68 kW. Apply with the actual design and compare the DNO’s single- and three-phase options.

Phase balance and tariff schedules

A single-phase home places all its net demand and export on one network phase. With three-phase, equipment and circuits can be distributed, but single-phase devices still load only the phase to which they are connected unless a genuine three-phase unit or coordinated system is used.

Cheap-rate schedules can create a new peak when the EV, battery, immersion heater and heat pump all start together. A design that appears acceptable from annual kWh can still overload the connection during that window.

Coordinate schedules or use a whole-site controller. Confirm what happens if internet access, a CT sensor or cloud service fails. The safe fallback must preserve the agreed import limit.

When three-phase becomes relevant

A three-phase connection becomes relevant where:

assessed demand cannot be kept within the available single-phase capacity
equipment requires a three-phase supply
a larger generation or storage scheme receives materially better connection terms on three phases
the site needs several simultaneous high-power charge points
voltage rise, phase imbalance or network constraints make the single-phase design unsuitable
planned future loads justify doing the civil and metering work once

Compare the actual connection offer, equipment changes, metering, consumer-unit work and phase allocation. A theoretical three-phase capacity calculation is not an offer from the DNO.