Peak electrical demand and all-electric heating

Going all-electric removes the gas connection and replaces it with a much larger electrical one. On a site of any size the question that decides the programme is whether the distribution network operator can supply the all electric heating grid capacity the scheme needs, and when. Nobody doubts that heat pumps work. Reinforcement is measured in months and sometimes years, and it sits outside the developer's control.

That makes the connection an evidence question for the planning application as much as a technical one. An energy statement that promises an all-electric strategy without any connection evidence is promising something the scheme may not be able to deliver on the assumed programme.

Why all-electric raises the connection question

A gas-heated house draws electricity for lighting, appliances and hot water only. An all-electric house draws it for space heating and hot water as well, and if it has a charge point it draws it for the car too. The peak coincides with a cold winter evening, which is also when the network is most heavily loaded.

Distribution network operators size connections using an after diversity maximum demand figure per dwelling, which assumes that not every home peaks at the same moment. The figures applied to all-electric homes with heat pumps and charging are materially higher than the assumptions used for gas-heated estates, and they have been revised as the evidence base has grown. Get the current figure from the network operator for your area rather than from a textbook or a previous scheme.

For flats the position is different again, because a communal system concentrates the load in a plant room and an individual system spreads it across a rising main that was sized on older assumptions. On a conversion or a retrofit that distinction often decides which strategy is feasible.

Estimating diversified peak demand

Do the arithmetic properly and show it. The submission needs a demand figure, the basis for it, and the design decisions that reduce it.

The components to set out are the space heating load at design conditions, the hot water load and how it is stored, the unregulated electrical load, any communal plant including lifts and ventilation, and the vehicle charging load after any load management. Then state the diversity assumption and where it came from.

Two design moves reduce the number materially. Fabric performance, because a heat pump serving a well-insulated dwelling at a low flow temperature draws less at peak than one compensating for a leaky envelope. And thermal storage, because a hot water cylinder charged outside the evening peak with a smart control shifts a significant part of the load to a time the network can serve. Batteries and photovoltaics help at the margin, and photovoltaic output at a winter peak is close to nothing, so do not claim it.

Say plainly which of these the scheme relies on. An Energy Statement that gives a single kilowatt figure with no derivation invites an officer to treat it as an assertion.

Network capacity and when to ask

Engage with the network operator at the point you have a site and a unit count, not at technical design. The sequence is a point of connection enquiry, a budget estimate, a formal connection offer, then the reinforcement and connection works themselves.

Each stage has a quoted turnaround, and the reinforcement works at the end are where the programme risk sits. Where the local network needs upstream work, the timescale is driven by the operator's own investment planning and by outages that can only be taken at certain times of year. That is not something a planning condition can shorten.

Two mitigations are worth pursuing in parallel. A flexible or curtailable connection agreement, under which the site accepts limits on import at defined times in exchange for an earlier and cheaper connection, can bring a scheme forward by a long way, and it has to be designed into the building services rather than bolted on. And an independent connection provider can carry out the contestable works, which sometimes compresses the programme.

Record all of this in the Utilities Assessment rather than leaving it in a consultant's email. An officer asked to grant permission for an all-electric scheme wants to see that someone has asked the question.

Substation space, access and easements

A new substation is a building with a footprint, an access requirement and a legal interest, and it is routinely drawn at the wrong size on planning drawings.

Allow for the operator's standard enclosure dimensions, the statutory clearances around it, vehicular access for a cable drum and for replacement of the transformer, and a route for the incoming cable that does not cross land you do not control. Then allow for the fact that the operator will want a lease or a transfer of the land with rights of access in perpetuity, which affects the layout and the plot boundaries.

Position matters for other reasons. A substation hums, so keeping it away from habitable rooms avoids an acoustic problem later, and the same logic applies to external heat pump units, whose noise is assessed against the relevant standards and whose position needs to be fixed at planning stage rather than left to the services engineer.

Where the site is phased, the electrical strategy has to work for each phase in isolation as well as for the whole, which is the same discipline described in our note on energy masterplanning across a phased site.

Storage, load shifting and what to claim

Load management is the difference between a connection that can be served and one that cannot, so describe it accurately.

Be careful with battery claims. A battery sized for daily solar shifting will not cover a multi-hour winter evening peak for a whole block, and an officer who has seen the same claim before will ask for the duration as well as the capacity.

Overheating pulls the other way and has to be reconciled in the same document. A fabric specification tuned for a low heating load can raise summer internal temperatures, which is assessed separately in the Overheating Risk Assessment against the relevant methodology, and councils normally expect a suitably qualified author for that work.

Evidence the application should carry

Assemble a short, specific package rather than a long generic one.

1. The connection enquiry or budget estimate from the network operator, with its date and reference.
2. The calculated diversified peak demand, with the assumptions listed.
3. The substation location, footprint and access shown on the layout, with the cable route.
4. The load management strategy, stated as design commitments rather than aspirations.
5. The noise position for external plant, with indicative positions fixed on the drawings.
6. A statement of what happens to the programme if reinforcement is delayed.

That last item is the one applicants leave out and officers most want. Saying that occupation of later phases depends on completion of the electrical infrastructure is not a weakness in the application; it is the basis for a sensible condition.

The decision about whether to take a gas connection at all is a separate question with its own commercial and policy dimensions, covered in our note on the all-electric new homes gas connection decision.

Conditions that tie occupation to capacity

A phasing condition is the usual mechanism, and it protects both sides. The wording restricts occupation of a defined part of the development until the electrical infrastructure serving that part has been provided and is operational, in accordance with details approved by the authority.

Two refinements make it workable. Define the parts by reference to a phasing plan rather than by plot numbers that may change. And keep the approval requirement to the infrastructure within the site, because a condition that makes occupation depend on works the network operator will carry out off site, with no reasonable prospect of a date, is a condition that fails the tests in the Planning Practice Guidance.

One honest uncertainty. The after diversity figures used for all-electric homes are still moving as metered evidence accumulates, so a demand estimate made today may be revised before the site is built out. Say in the statement which figure you used and when you obtained it.

PlanScope can draft the Energy Statement, Sustainability Statement and utilities narrative in minutes, structured to UK planning policy, ready for your engineers to check. Enter your postcode on PlanScope to see which reports the site is likely to need.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.