Planning one or two charge points for staff vehicles is a relatively straightforward job, requiring perhaps a site visit, a load check and a few metres of cable. But once you’re looking at ten or more vehicles returning to the same site each night, it’s a completely different proposition.
Grid capacity, phased cabling, DNO applications and load management all come into play, and the decisions you make at the start will either save you significant cost later, or leave you with infrastructure that can’t grow.
This guide is for fleet managers, operations directors and procurement leads who are scoping a fleet electrification project and want to understand what’s actually involved before talking to a contractor. Our commercial EV charger installation service covers the full scope from site survey through to commissioning, and the points below reflect what we see on the ground when businesses start this process.
Start With Fleet Size and Charging Patterns, Not Charger Numbers
The question most operators ask us is: how many chargers do I need? But this really isn’t the right place to start. Instead, the right questions are:
- How many vehicles return to base each night
- What is the average daily mileage?
- How long is the dwell window?
- What charge level do vehicles need to be at when they leave the next morning?
Let’s take a quick look at an example:
A 20-vehicle light commercial fleet covering 80 miles a day returns to depot at 6pm and leaves by 7am. That’s a 13-hour dwell window. At 7kW per charger, each vehicle picks up roughly 91kWh overnight, which is well in excess of what a typical electric van needs for 80 miles. This shows that you don’t need rapid chargers and you probably don’t even need all 20 chargers running simultaneously, if you stagger start times through a load management system.
Here’s another example:
A 50-vehicle fleet with mixed shift patterns, short dwell windows and vehicles doing 150 miles a day is a completely different infrastructure project. Some vehicles may need 22kW AC charging to recover enough range between shifts, while others may tolerate overnight 7kW just fine. The mix matters, and no two depots are the same.
With this in mind, the place to start is a proper demand analysis: vehicle types, daily mileages, return times, departure times, and target state of charge at departure. This analysis drives everything else, including how much grid capacity you actually need.
What Your Site Can Actually Handle: Power Capacity and Grid Constraints
Existing supply capacity is the first limiting factor on any fleet charging project, and it catches more operators off guard than any other single issue.
A typical commercial building on a 100A three-phase supply has a theoretical maximum demand of around 69kW. If you add 20 simultaneous 7kW chargers you’re drawing 140kW, which immediately exceeds that supply. For most sites, adding fleet charging means either upgrading the supply or managing the load carefully enough that you never draw close to the limit.
Where a significant capacity increase is needed, your business must apply to its Distribution Network Operator (DNO) for a new or upgraded connection. The DNO is the regional company responsible for the cables and substations that deliver power to your site.
Under government guidance on connecting EV chargepoints to the electricity network, the DNO will assess whether the local network has the capacity to accommodate the new load and issue a connection quote, which can take anywhere from 5 to 65 working days, depending on connection size. For larger schemes requiring significant reinforcement, the full process including design, quotation and physical works can run to 6 months or more.
That timeline is the single most common cause of fleet charging project delays, and operators who start the contractor conversation in October and expect chargers by January rarely get there. The DNO process sits outside your contractor’s control and the only way to manage it is to start early and engage a contractor who will notify or apply to the DNO on your behalf as soon as the site survey is complete.
For smaller installs on sites with existing headroom, a full DNO application may not be required at all. Some projects proceed with a notification only, which is a much faster process. Either way, a qualified site survey will tell you which route applies.
Load Management: Getting More From the Supply You Already Have
Smart charging systems don’t simply plug vehicles in and draw full power simultaneously. They distribute the available supply across all connected chargers dynamically, adjusting each vehicle’s charge rate based on how much headroom remains on the site’s electrical supply. This is called dynamic load balancing, and it’s a significant part of making fleet charging work on sites where the supply is constrained.
Take the same 100kW supply shared across 20 chargers. Rather than each charger attempting to draw 7kW and overloading the supply, the system throttles each one to an average of 5kW. For a vehicle with a 13-hour dwell window, that still delivers around 65kWh overnight, which covers most light commercial vehicle requirements.
The other tool in the load management toolkit is time-of-use tariff optimisation. Most business electricity tariffs are cheaper between 11pm and 6am. A properly configured smart charging system will schedule the bulk of charging for those hours, reducing your overnight electricity costs substantially. For a 20-vehicle fleet, the difference between charging at peak and off-peak rates adds up quickly across a year.
The practical benefit of getting load management right is that it can push back the point at which you need a DNO supply upgrade, potentially by a significant margin. That’s a real project cost saving, not just a theoretical one. It doesn’t eliminate the need for a larger supply as your fleet grows, but it buys time and reduces the urgency of the initial capital spend.
| Planning a fleet charging rollout? Our commercial EV charger installation service covers the full scope from site survey through to commissioning, including DNO applications and load management setup. Get in touch to arrange a site assessment. |
Phasing Your Infrastructure Rollout
Most fleet operators don’t need to electrify all their vehicles at once. The ZEV mandate requires 80% of new cars and 70% of new van sales to be zero emission by 2030, and 100% of all new car and van sales to be zero emission by 2035. It’s worth noting that the April 2025 mandate updates, while leaving those headline targets unchanged, introduced greater flexibility in how manufacturers meet them, including allowing new ICE vans to be sold until 2035. In practice, this means the transition timeline for van availability is more gradual than the original mandate implied, and fleet operators have more room to phase in electrification than the top-line figures suggest. With that in mind, a phased approach is both practical and financially sensible.
The key insight is that the phasing of charger installations and the phasing of the infrastructure underneath them are two different decisions, and the second one should be made in full for the eventual fleet size, even if the first is made incrementally.
Here’s what that looks like in practice:
- Phase 1: Install cabling, containment and consumer unit capacity sized for the full eventual fleet, but only fit the number of chargers you need now. The groundworks are the expensive part. Digging trenches twice costs far more than leaving empty conduit in place.
- Phase 2: As your fleet grows and more vehicles return to base each night, add chargers into the existing infrastructure. This is a relatively minor electrical job if the groundworks were done correctly the first time.
- Phase 3: Apply for the DNO supply upgrade when load management data shows you’re consistently hitting the headroom limit. By this point you have real consumption data to support the application, and you’re not paying for a supply upgrade before you actually need it.
The design decision made in phase one determines how expensive or straightforward phases two and three will be. Bear in mind then that a contractor who quotes only for the chargers you need today, without accounting for future growth, will leave you with cable routes that can’t carry additional load, a consumer unit that has no spare capacity, and groundworks that will need to be opened up again.
Ask any contractor you speak to how they approach the infrastructure sizing question, and if the answer is based purely on current vehicle numbers, that is a red flag. Our approach to commercial EV charger installation starts with where your fleet will be in five years, not where it is today.
What to Expect From the Installation Process
The stages of a properly scoped fleet charging installation run roughly as follows:
- Site survey and power assessment: A qualified engineer visits the site, checks the existing supply, measures available headroom, and maps the proposed cable routes and charger positions.
- Load modelling: Based on the fleet demand analysis and the site survey findings, the engineer calculates peak and average load, confirms whether load management alone is sufficient or a DNO upgrade is required, and sizes the infrastructure accordingly.
- DNO notification or application: For smaller installs on sites with spare capacity, the contractor notifies the DNO and can proceed. For larger schemes, a formal connection application is submitted and the project waits for the DNO’s assessment and quote before works begin.
- Design sign-off: The full electrical design is documented and agreed before any groundworks start.
- Groundworks and cabling: Trenching, containment, cabling runs and any required works to the consumer unit or distribution board.
- Charger installation and commissioning: Chargers are fixed, wired and commissioned. Load management software is configured and tested.
- Handover: Full documentation is provided, load management software is set up for your team, and any monitoring or reporting tools are configured.
The important thing to understand about this process is that a quote based on charger numbers alone, issued without a site visit, can’t account for any of the infrastructure questions that drive actual project cost and timeline.
Before you commit to a contractor, make sure they’ve visited the site and confirmed the cable routes, the consumer unit capacity and the DNO position.
For further context on what the hidden costs of EV charger installations can include, and for a broader look at why more businesses are investing in workplace EV charging, the linked articles cover both in more detail.
| If you are at the scoping stage, the best first step is a site assessment. We’ll confirm your supply capacity, identify the DNO route and give you a realistic picture of what your fleet charging infrastructure will cost and how long it will take. Find out more about our commercial EV charger installation service, or use our contact page to get in touch directly. |