Utilities capacity checks before you fix a unit number

The number of homes a site can deliver is often set by a substation rather than by policy. A utilities capacity check development enquiry costs very little, takes a few weeks, and tells you whether the electricity network can accept your load without reinforcement, whether the water main can deliver the pressure and flow, and whether the sewer downstream has capacity. Run those enquiries before the unit number is fixed, because reinforcement costs and connection lead times change the arithmetic of a scheme more reliably than planning policy does.

The pattern to avoid is familiar: a layout optimised for policy compliance, a permission granted, and then a connection offer that makes the last phase unviable.

Enquiries to make and to whom

Four organisations, four separate enquiries, all of which can run in parallel during the design stage:

• the electricity distribution network operator for the area, for a point of connection and a budget estimate
• the water undertaker, for a pre-development enquiry covering pressure, flow and the point of connection for a new main
• the sewerage undertaker, usually the same company, for foul and surface water capacity
• the telecommunications providers, for a new site connection and the timescale for provision

Each will ask for the site boundary, the proposed number and type of units, the expected load or demand, and a programme. Give them the honest maximum rather than the conservative figure, because an offer based on 40 units does not cover 60, and the second enquiry starts the clock again.

Ask for the response in writing and keep it, since the planning application benefits from being able to say that capacity has been confirmed. A Utilities Assessment is the document that collects those responses in one place.

Electricity capacity and reinforcement

The distribution network operator will state the point of connection, the capacity available at that point, and any reinforcement required upstream, with a budget estimate for the works. Three things in that response matter more than the headline figure.

First, whether a new substation is required on site. If it is, it needs land inside the red line, an access route for a delivery and maintenance vehicle, and an easement, and all three affect the layout. A substation placed at the end of the design process lands on a plot.

Second, whether reinforcement is needed, and how the cost is apportioned. Reinforcement costs can be large and are recovered under the connection charging arrangements, which change from time to time, so treat the estimate as a figure to verify rather than a fixed price.

Third, the load assumption. All-electric schemes with heat pumps and electric vehicle charging draw substantially more than a gas-heated equivalent, and diversity assumptions differ between operators. If the design moves to all-electric after the enquiry, the enquiry is out of date.

Water supply pressure and flow

Pressure is the constraint that surprises people, particularly on higher ground or at the end of a long main. The undertaker's pre-development enquiry gives an indication of available pressure and flow at the proposed connection point, and the answer determines whether a boosted supply is needed for upper floors and whether a sprinkler system, where required by the building regulations, can be fed from the mains at all.

Where a new main is needed, it is requisitioned under the water industry legislation, with the costs and the timescale set out in the undertaker's offer. Where the route crosses third party land, easements are needed, and that has been known to take longer than the planning application.

Put the water answer next to the sprinkler requirement early. A residential block above 11 metres needing sprinklers, on a site where the mains cannot deliver the flow, needs a tank and pump set with a plant room, which is a planning drawing issue and not a detail.

Foul capacity and the undertaker's response

There is a right to connect to a public sewer under the water industry legislation, and it is not an unqualified one: the undertaker can require the connection to be made at a different point, and capacity problems are addressed through its own programme rather than by refusing connection.

What the undertaker's response tells you is whether the downstream network has capacity, whether a connection is available at the point you want, and whether phasing is needed to align with a network upgrade. On sites where capacity is constrained, councils frequently impose a Grampian style condition preventing occupation until the necessary upgrade is complete, and that condition governs your sales programme. Our note on statutory consultees that appear as a scheme grows sets out when the undertaker becomes a consultee in its own right.

Surface water is a separate answer again, and the hierarchy of discharge, infiltration first, then watercourse, then sewer, means a sewer connection for surface water is often refused outright. The Foul Sewage Assessment and the drainage strategy record both positions.

Gas and telecommunications

Gas matters less than it did, and on many schemes not at all, though an existing gas main crossing the site still needs identifying, because diversions are slow and the easement restricts what can be built over it.

Telecommunications is now a building regulations matter as well as a commercial one, with a requirement for gigabit ready physical infrastructure and, where reasonable, a connection to a gigabit capable network. Registering the site with the network providers early is worthwhile, since new site provision runs to months rather than weeks and purchasers notice its absence.

Lead times against the build programme

Set the utilities answers against the programme as a table, with the enquiry date, the validity period of each offer, the acceptance deadline and the lead time from acceptance to energisation or connection.

Two traps recur. Offers expire, and an expired offer means a new enquiry at current prices and current capacity, which may have been taken by another developer in the meantime. And long lead items, transformers and switchgear in particular, have had extended delivery periods in recent years, so an energisation date has to be treated as a programme risk rather than a fixed point.

Where reinforcement or a network upgrade is needed, ask what triggers the upgrade and whether another development in the area is already funding it. Sharing a reinforcement with a neighbouring scheme is common and can halve the cost.

Feeding the answers into the scheme size

Then do the arithmetic that the exercise exists for. Reinforcement and connection costs divided across the units gives a cost per plot, and that figure belongs in the appraisal next to the section 106 and levy assumptions, because it competes with them for the same margin.

Sometimes the answer is fewer units in phase one with capacity released later. Sometimes it is a different heating strategy to reduce the electrical load. Sometimes it is a substation on the least valuable corner of the site, designed in from the start. All three are better than discovering the constraint after permission, and each of them is easier to argue in a viability discussion when the evidence is a written offer from the network operator rather than an estimate.

The report types by category page shows where the utilities evidence sits in a major application pack.

This is general guidance, not legal advice; take the figures from the network operators and undertakers themselves, and check the current connection charging arrangements before relying on any estimate. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.