The short answer
For a small, low-complexity building — a single-storey office, a small care home, a shop with a kitchen and washrooms — a competent Legionella risk assessment typically costs between £250 and £450 in 2026.
For a medium commercial building with multiple floors, plant rooms and a more complex hot and cold water system, expect roughly £450 to £900.
For large, high-risk or healthcare estates — hospitals, multi-building campuses, sites with cooling towers or calorifiers — assessments run from £900 well into the low thousands, and are often priced per building across a portfolio.
Those are realistic 2026 UK ranges, not headline 'from £99' marketing numbers. A genuinely competent assessment of anything beyond a tiny premises does not cost £99 — and that gap is where most of the risk hides.
What actually drives the price
The single biggest cost driver is the number of outlets and assets. Every tap, shower, calorifier, cold-water storage tank, expansion vessel and dead-leg has to be located, assessed and recorded. A building with 12 outlets is a fundamentally smaller job than one with 200.
System complexity is next. A simple mains-fed direct system is quick to assess. Stored systems, recirculating hot water, multiple plant rooms, mixed-age pipework and previous unrecorded alterations all add time — and time is what you're paying for.
Risk profile and sector matter too. Healthcare and care settings carry vulnerable occupants and trigger HTM 04-01 expectations on top of ACOP L8, so the assessment is more thorough. Cooling towers bring HSG274 Part 1 into scope and raise the bar again.
Finally, access and condition. If plant rooms are locked, roof tanks need ladder access, or the existing records are missing, the assessor spends longer on site. Good record-keeping on your side genuinely lowers the cost on ours.
What a proper assessment includes
A competent Legionella risk assessment to BS8580-1 should always include: a full survey of the water system; an asset register listing every relevant outlet and item of plant; an up-to-date schematic of the system; an evaluation of the risk at each point; and a prioritised, time-bound remedial action register.
It should also confirm — or recommend — a written scheme of control specific to your site, and identify who your 'responsible person' is. If a quote doesn't mention a schematic, an asset register and a remedials register, it isn't a full BS8580-1 assessment, whatever the price says.
You should receive the written report within a sensible window of the site visit — we issue ours within 48 hours — and it should be in a format your insurer, auditor or HSE inspector will accept without follow-up questions.
The cheap-quote traps
A surprisingly large share of 'budget' assessments are carried out by an unqualified surveyor with a clipboard, producing a generic template with the site name changed. These fail audit, and an HSE inspector will probe assessor competence aggressively after any incident.
Watch for quotes that exclude the schematic, that don't commit to an asset register, or that are priced 'per visit' with the report as an expensive add-on. Watch, too, for assessments that quietly omit cooling towers or infrequently-used outlets to keep the headline price down.
The real cost of a bad assessment isn't the fee — it's the false sense of compliance. If the assessment misses a risk and someone is harmed, the duty holder carries unlimited fines and potential personal liability. The few hundred pounds 'saved' is irrelevant against that.
Cost versus risk — the honest framing
A competent annual or biennial Legionella risk assessment is one of the cheapest pieces of statutory compliance a building operates. Set against the cost of a confirmed outbreak — closure, remediation, investigation, legal costs, reputational damage and potential prosecution — the assessment fee is a rounding error.
The sensible way to think about price is therefore not 'what's the cheapest quote' but 'who is competent, what's actually included, and will this stand up if it's ever tested'. On that basis, the spread between a good assessment and a cheap one is small — and the downside of getting it wrong is enormous.
How we quote
We quote on scope, not guesswork. A free site survey — or a structured phone conversation about your building, outlet count and system type — lets us give you a fixed price rather than a vague 'from' figure. For multi-site portfolios we price per building and bundle the programme.
You'll have the quote within 48 hours, it will list exactly what's included, and the engineer who'd carry out the work is the person who scopes it. No call-centre, no bait-and-switch on the day.