Avoid £3,600 Connection Costs: Building Regs Part S for UK Developers
Part S applies if your project is a new residential or non-residential building, a material change of use, or a major renovation with parking, and it became mandatory in England in mid 2022. Headline obligations include active charge points with a 7 kW minimum, smart-charging capability, untethered sockets where required, and cable routes for extra spaces once you pass 10 parking bays. First step: confirm your building type and count associated parking, then speak to building control and a qualified installer.
TL;DR:
All mandated charge points must have a minimum output of 7 kW, smart-charging functions, dedicated circuits, and proper fault protection according to BS 7671 standards.
Projects submitted before June 15, 2022, or with connection costs above approximately £3,600 per point, may qualify for exemptions or deferred installation.
Proper planning involves early load assessments, detailed cost estimates, and clear parking allocations to prevent delays and costly rework during installation.
Grid connection timelines and limited electrical capacity often pose the biggest obstacles, making early engagement with DNOs and load management essential.
Table of Contents
What is Approved Document S and which projects does it cover?
Approved Document S is the technical guidance that supports Part S of Schedule 1 to the Building Regulations 2010. It tells you what “compliant” actually looks like on site: how many charge points, what cable routes, and to what electrical standard.
The guidance splits scope into six categories, labelled S1 to S6:
S1 covers new residential buildings with associated parking.
S2 covers residential buildings undergoing a material change of use.
S3 covers residential buildings undergoing major renovation.
S4 covers new non-residential buildings.
S5 covers non-residential buildings undergoing major renovation.
S6 covers mixed-use developments, apportioned between the categories above.
Approved Document S applies in England. If you’re working across borders, check local building-control expectations directly, since devolved administrations run separate regimes.
How many charge points and cable routes does your project need?
The numbers differ sharply between residential and non-residential schemes, and mixed-use developments need the calculation done twice.
Residential new-build (S1): every dwelling with associated parking needs either an active charge point or, at minimum, the cable route to install one later. A 12-flat development with 12 allocated bays needs 12 charge point provisions, full stop. There’s no “1 in 5” discount here.
Residential material change of use or major renovation (S2/S3): the same principle applies where parking already exists or is being created. Each dwelling served by that parking should have a charge point or cable route unless an exemption applies.
Non-residential new-build or major renovation (S4/S5): this is where the one-in-five rule kicks in. Once a scheme has more than 10 parking spaces, you need:
At least one active charge point.
Cable routes for a minimum of one in five of the remaining spaces.
A retail unit with 40 spaces, for example, needs one live charger plus cable ducting ready for roughly eight more.
Mixed-use (S6): apportion the total parking between residential and non-residential use, then apply the relevant rule to each portion separately. A ground-floor retail unit under 30 flats treats the retail bays under S4/S5 and the residential bays under S1, rather than blending the two into one calculation.
What technical standards must the installation meet?
Meeting the parking-space count is only half the job. Every mandated charge point needs a minimum nominal rated output of 7 kW and smart-charging capability under Regulation 44J, meaning it can respond to signals that shift charging away from peak demand periods. Untethered sockets are the default expectation, with tethered cables generally accepted only in specific circumstances such as fleet or controlled-access sites.
On the electrical side:
Dedicated circuits are required, not shared spurs off existing sockets.
BS 7671 Section 722 governs earthing and fault protection for EV charging circuits specifically.
RCD selection (Type A, F, or B, or an RDC-DD device) depends on the charger’s own built-in DC fault-detection, so the installer must check the manufacturer’s spec sheet, not assume.
Every installation needs commissioning tests, a completion certificate, and clear labelling before handover.
The IET Code of Practice for Electric Vehicle Charging Equipment Installation sits alongside BS 7671 as the reference document your electrician should be working from, and it’s worth asking to see it referenced on the design.
Roughly one in five remaining bays needs a cable route on qualifying non-residential sites, which is the figure that trips up estimators most often when they price a job from the active-charger count alone.
Pro Tip: Ask your installer which RCD type the charger’s datasheet specifies before wiring design starts. Getting it wrong at first fix means ripping out first-fix cabling later.
When can you delay installation, and what costs trigger an exemption?
Two dates matter more than any other figure in Part S. If you submitted a building notice, full plans application, or initial notice before 15 June 2022, and started work on site before 15 June 2023, the new rules likely don’t apply to your project. Everything submitted after that first date falls under Part S in full.
Cost is the second lever:
Get formal connection quotes from your Distribution Network Operator or electrical contractor for each mandated charge point.
If the average connection cost per point comes out above roughly £3,600, you may install cable routes only and defer the active charger.
Keep both quotes on file. Building control will want evidence, not a verbal estimate, before accepting the cheaper route.
Other exemptions cover sites with no associated parking, covered car parks where the wider parking count rule doesn’t bite in the same way, and some heritage or disproportionate-cost cases assessed individually.
Compliance checklist: what to confirm before work starts
Run through this before your electrician arrives on site, rather than after:
Confirm building category (S1 to S6) and count every associated parking space, including visitor and accessible bays.
Decide, space by space, where you need an active charge point versus just a cable route.
Commission an early electrical load assessment and request a connection-cost estimate from your supplier or DNO.
If costs sit near the £3,600 threshold per point, get two written quotes and keep them for building control.
Specify dedicated circuits, correct RCD type, and full commissioning tests in the electrical scope.
Require compliance certificates and labelling on completion, not as an afterthought.
Future-proof spare bays with cable routes and clearly labelled future connection points, even where not strictly mandated yet.
Pro Tip: Building control inspectors increasingly ask for the load assessment paperwork alongside the electrical certificate. Have both ready at first-fix inspection, not final sign-off.
What site risks catch developers out on real projects?
Communal electrical supply capacity is usually the constraint that decides a project’s fate, not the Approved Document itself. On blocks fed by a single landlord supply, diversity allowances can’t be relied on the way they can for individual dwellings, so load calculations need to be conservative and often point towards a new supply.
Where a full upgrade isn’t affordable, load-management systems, array-based charging, or staggered smart controllers can bring several charge points onto one modest supply without tripping the main fuse. Grid-connection timelines from DNOs can run to several months on constrained networks, so build that into your programme early rather than discovering it after tender.
Some landlords and flat owners can access grant support that changes what’s worth specifying upfront.
Get a load assessment done before finalising the electrical design, not after.
Loop in your installer and building control together, early, so design and sign-off aren’t fighting each other later.
A practitioner’s view on where Part S projects go wrong
Most delays trace back to the same three mistakes: load assessments done too late, connection costs underestimated at feasibility stage, and parking allocation left ambiguous on mixed-use schemes until building control asks awkward questions.
Swift Charging works with property owners and developers from site survey through to design, grant application support, and the compliance paperwork building control actually wants to see. Bring us in before the electrical design is fixed, not after.
— Swift Charging
Get Part S compliance sorted before it becomes a site problem
Getting Part S right on paper is one thing. Getting a compliant, commissioned installation onto a live site, on budget, is another, and that’s the gap Swift Charging closes for property owners, builders and developers across the south of England. We run the site survey, design the electrical scheme to BS 7671 and the IET Code of Practice, handle installation and commissioning, and hand over the certificates building control will actually ask for.
If your connection costs are hovering near the £3,600 threshold per point, or you’re not sure whether your parking count triggers the one-in-five cable-route rule, get that checked before you commit to a design. We also help clients assess eligibility for available EV charging grants, which can shift the specification worth installing now versus deferring. If you’re delivering a scheme in the south, our commercial EV charging installation team in Chichester can walk through your site requirements and give you a realistic cost picture before you go back to building control. Request a site survey and we’ll tell you plainly what your project needs.
Where to check the official rules yourself
Read Approved Document S and its full technical PDF directly, alongside BS 7671 guidance and Swift Charging’s EV infrastructure articles.
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