Three weeks ago, an electrical contractor I work with lost a £312,000 tender by £1,400. Not fourteen thousand. Fourteen hundred. 0.45% of the total. He thought it was bad luck. It wasn't.

It was a margin leak — and once we found it, he saw the same leak in the last six tenders he'd lost.

When you lose by single-digit percentages repeatedly, it almost never points to bad luck or a cut-throat competitor. It points to systematic leaks in how you're pricing. Here are the six leaks we see most often in UK electrical estimating — and what to fix in each.

Leak 1

Preliminaries that aren't really priced

Preliminaries — the costs of being on site that aren't tied to a single trade — are where the largest single percentage of bids leak. Site supervision, scaffolding access charges, welfare facilities, temporary power, waste removal, programme contingencies. Most estimators apply a flat 8–12% mark-up to cover them and call it done.

That works for jobs you've done before. On unfamiliar projects it routinely under-funds the prelims by 2–4% of contract value. On a £312k tender, that's £6,000–£12,000 of cost you're absorbing without realising.

The fixItemise prelims rather than applying a percentage. Even a rough line-by-line — site supervisor days, parking permits, scaffolding hire weeks — surfaces the missing cost.
Leak 2

Subcontractor enquiries that aren't really subcontracted

This is the most common leak we see. The estimator marks a sub-package in the BOQ as "subcontracted" and applies a placeholder rate from a previous job — without actually sending an enquiry to a current sub.

The placeholder rate was right twelve months ago. It isn't right today. Sub rates for fire alarm install, data cabling, and BMS commissioning have moved by 8–18% in the last 18 months alone.

The fixSend live enquiries on every tender, every time. Track sub response rates so you know which subs respond inside 48 hours and prioritise them on tight deadlines. A REMC tender response sends an average of 3–5 sub enquiries per tender, chases them at 24 and 48 hours, and uses a "live rate or no rate" rule — placeholders are never carried into a final submission.
Leak 3

Materials priced from yesterday's prices

Wholesaler pricing on the UK electrical market is genuinely volatile right now. Copper, aluminium, switchgear, and LED luminaires have all moved 5–12% over the last six months in ways that don't filter through to the monthly trade price list immediately.

Estimators relying on Excel spreadsheets with materials prices last updated three months ago are systematically under-pricing — or worse, over-pricing and losing on the bid.

The fixGet live quotes from your preferred merchants on every material-heavy tender. Yes, it adds two hours of work. It also stops you from losing a £312k job by £1,400.
The qualifications library we use on every tender

30+ tested clauses that protect margin on every UK electrical tender. Inside the Commercial Templates pack.

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Leak 4

Labour hours estimated from gut, not data

How long does it take to install a 32A radial circuit in a domestic property? How long to terminate a 2nd-fix lighting point in a commercial fit-out? Most estimators will give you a confident answer — but when you cross-check against actuals from completed jobs, the variance is often 20–40%.

The estimator's gut is calibrated to one period of their career. The market moves. Crew composition changes. Site conditions vary by region. If you're not adjusting your labour rates against your own delivered job data, you're systematically wrong.

The fixBuild a feedback loop. Every completed job updates your labour-rate library. Estimators who price using actual recorded data from your last twelve months win at materially higher rates than ones priced on memory.
Leak 5

Missing qualifications that swallow risk you didn't price

This is the leak that hurts most when it becomes a live job — not at tender stage.

Tender packs are full of small clauses that shift risk onto the contractor: undefined access windows, pay-when-paid sub clauses you didn't notice, retention release schedules tied to the main contractor's certification, programme penalties of £500/day.

If you don't qualify them out at tender, you're absorbing them at delivery — at 100% of your margin's expense.

The fixMaintain a standing qualifications library — 30+ tested clauses ready to drop into any submission. Read every tender pack against the library and flag every clause you'd qualify.
Leak 6

Mark-up maths that doesn't add up

Last leak, often the most embarrassing. Most estimators apply mark-up correctly to materials but apply it inconsistently across labour, plant, sub-packages, and prelims. Or they apply gross-up where they meant net, or net where they meant gross.

A single mis-applied mark-up on a £40k sub-package costs you 1.5–2.5% on the total bid. On three out of every ten tenders you submit, by the time the mark-up errors compound, you're 3–5% off where you intended to be.

The fixA single locked mark-up calculator that every estimator in your team uses. No freelance Excel sheets. No "I'll just multiply it in my head". One source of truth, audited monthly.
1 in 4

The contractor we mentioned at the start tightened up four of these six leaks. His tender win rate moved from 1 in 7 to 1 in 4. Same volume, more wins, identical mark-up policy.

The leaks compound. So does the fix.

You don't need to fix all six at once. Most clients we work with knock out the top three in their first month and see a measurable win-rate change within a quarter. The remaining three follow as the workflow matures.