We installed 200 chargers last year. Here are the 5 things that always go wrong.

We've delivered more than 200 commercial EV charging installs across the UK. About a quarter of them ran clean from kick-off to commissioning. The other 150-odd taught us something useful: the same five things go wrong, in roughly the same order, on roughly the same percentage of projects. Each one costs between £400 and £1,200 a day in delay. A 9-day slip on a depot install is £7,650 out of someone's budget, and that someone is usually you.

Here's the part nobody else in the industry will say out loud. The villain isn't bad luck. The villain is vendors who sell you a "smooth, turnkey installation" in the pitch deck and then vanish the moment the snag list appears. The signature dries, the named project manager goes "on leave," and your facilities team is suddenly emailing a generic support address about a Victorian fibre cable nobody surveyed.

We're going to walk you through the five things — ranked by how often they hit — and tell you the contract language that makes the vendor pay for the problem instead of you.

The five things, ranked by frequency

These percentages are from our internal post-install reviews across 200+ commercial sites between 2021 and 2025. Your site won't dodge all of them. With the right contract, it shouldn't matter.

1. Unmapped buried services during trenching (hits ~42% of sites). Statutory undertaker plans are wrong, incomplete, or genuinely from 1973. Trench goes in, fibre comes out, day stops. Typical delay: 3–14 days while the asset owner authorises a repair and re-survey. Typical day-cost on a depot install: £850/day in standing labour, plant hire and rescheduled commissioning slots.

2. Hardware shipment delays or wrong SKU arriving on site (hits ~31% of sites). The unit ordered isn't the unit on the pallet. Or the right unit is on a container off Felixstowe. Or your "in-stock" charger has a 16-week firmware-locked supply chain nobody mentioned. Typical delay: 2–6 weeks. Typical cost when contractors are demobbed and remobbed: £600–£1,100/day equivalent.

3. DNO reinforcement quote arriving at sign-off (hits ~24% of sites). You scoped for an 11kVA upgrade. Your DNO reviews the application and quotes you £180,000 for transformer reinforcement and an 18-month timeline. This should have surfaced at site survey. It surfaces three weeks before commissioning instead, because the installer never actually filed the G99 in time. The single most expensive delay on this list when it lands late.

4. Firmware or OCPP version mismatch between charger and back-office (hits ~22% of sites). The unit speaks OCPP 1.6J. The back-office expects 2.0.1. Or both speak 1.6J, but the vendor has a "proprietary extension" that breaks roaming. Commissioning fails. Two weeks of back-and-forth between hardware vendor and software vendor while both blame each other. Cost: £400–£700/day, plus reputational damage with whoever signed off the project.

5. Commissioning failure from underspec'd cabling (hits ~18% of sites). The cable laid is rated for 100A. The unit pulls 125A continuous at full duty. It works for ten minutes, trips, and won't recommission. You're now digging up a freshly-laid trench. Cost: £1,000–£1,200/day plus the rip-out, redo, and reinstate civils — frequently another £12,000–£25,000 of capex.

That's five problems. On a typical 8-socket depot install that runs 6–10 weeks, you'll hit at least two of them. The question isn't whether you'll get unlucky. The question is whether your contract makes it the vendor's problem or yours.

Worked example: an 8-socket depot, Coventry, late 2024

This is a real site, anonymised. 8 × 22kW twin AC chargers behind a fleet of light commercial vans. Programme: 8 weeks from civils start to handover.

• Week 1: Civils begin. Trench survey identifies utilities from the 2008 statutory plan. Looks clean.
• Week 2: Day 3 of trenching, the excavator finds an unmapped Victorian-era fibre conduit servicing a neighbouring industrial estate. Trip number 1. Trench halts. Asset owner notified. Repair authorised after 9 days.
• Delay cost calculation: 9 days × £850/day = £7,650 in standing labour, hire return penalties, and rescheduled DNO commissioning slot.

In this case the contract included a liquidated damages clause for delays attributable to civils discovery — capped at the daily cost agreed at the survey stage. The £7,650 was deducted from the next milestone payment. Net cost to the client: £0. Net cost to whoever sold them "a smooth turnkey install": £7,650.

The other four risks also showed up across the project — a firmware mismatch (resolved in 4 days), a DNO timeline extension on socket 7 and 8 (resolved by rephasing the install), and one wrong-SKU pallet (caught on goods-in and rejected before unloading). Total delay: 16 days across 56-day programme. Total cost recovered via the contract: £14,200.

This is what good looks like. It isn't that nothing went wrong. It's that the vendor wore the cost.

The contract clauses that save you

If your installer gives you a 4-page contract with "best endeavours" and "industry-standard timelines" in it, you do not have a contract. You have a wish.

Here's what should be in it, in plain English:

• Liquidated damages for delay. A named £/day figure for every day the programme overruns, attributable to vendor causes. Surveyed-civils discoveries are vendor-cause if the vendor did the survey. Make sure that clause exists.
• Surveyed-civils fixed pricing. Trench rates per metre, locked at survey stage, with discovery contingency allocated to the vendor not the client up to a named threshold (e.g. first £15,000 of unexpected civils on vendor).
• Named back-office at signing. Not "compatible with most major back-offices." The specific platform name, the OCPP version, the firmware version of the unit on the day it ships. In writing.
• DNO filing milestone with penalty. G99 application filed within 10 working days of contract signature, evidenced. Late filing triggers daily penalty. This single clause prevents problem #3 entirely.
• Hardware substitution requires written approval. No "equivalent" units. The SKU on the pallet must match the SKU on the contract.
• Commissioning warranty. 90-day post-commissioning warranty covering recalls, firmware patches, and OCPP integration. Vendor covers all costs including site visits.

You can copy and paste those six bullets into your next vendor RFP. We won't be offended.

The supplier discipline that prevents most of it

Here's the boring truth: about 75% of these delays are preventable upstream of the contract.

A real site survey takes a half-day on site, not a desktop drive-by from Google Earth. The DNO filing happens in week 1 of the contract, not week 6. Hardware is ordered to a written SKU lock with a named ship-date. The back-office is contracted by name, version and integration test pre-shipment. Civils trenching follows a fresh GPR (ground-penetrating radar) survey, not a 17-year-old utility map.

If your installer doesn't do those four things by default, change installer. The £400-a-day delay risk is real money, and you're paying for it whether you can see the line item or not.

What to ask before you sign

1. "How many commercial installs have you actually delivered in the last 24 months — and can I speak to two of them?"
2. "Show me your contract's liquidated damages clause."
3. "What's the exact back-office platform, OCPP version, and firmware version going on my unit?"
4. "When will the G99 be filed, and what's the penalty if it slips?"
5. "Who runs your civils survey, and can I see a recent GPR report?"

Vague answers to any of those, walk. There are 200+ commercial installers in the UK who'll answer all five with a straight face.

The short version

Five things go wrong on EV install projects, in roughly this order of frequency: unmapped buried services, hardware delays, late DNO reinforcement, OCPP mismatch, underspec'd cabling. Each costs £400–£1,200/day in delay. Six contract clauses move the cost from your budget to the vendor's. Most of it is preventable with a proper site survey, an early DNO filing, and a written SKU lock. None of it is preventable by trusting a brochure.

Want us to do the maths on your site?

Book a site survey at /site-survey. We'll come out with the ground-penetrating radar, file your G99 within 10 working days of signature, and put the liquidated damages clause in writing before you commit a pound. Especially the LD clause. That's the one that costs us money when we get it wrong.