Day rate or fixed price? How to compare Power BI quotes

Ask for a day rate and you learn what somebody's attention costs. Ask for a fixed price and you learn what they think the job is. The second is far more useful, because the number that decides your budget is not the rate — it is the day count, and that is what suppliers actually disagree about.

What each pricing model actually transfers

The difference between the two is not administrative. It is about who carries the risk that the estimate is wrong.

	Day rate (time and materials)	Fixed price
Who carries estimating risk	You	The supplier
What you approve up front	A rate	A deliverable and a total
What happens if it takes longer	You pay more	The supplier absorbs it
What happens if scope changes	Absorbed silently	Visible change request
Best suited to	Discovery, support, open backlogs	A defined first build
Main failure mode	Drift, no natural stopping point	Under-scoping, then padding

Neither is virtuous. A fixed price is only meaningful if the scope behind it is written down, and a day rate is only dangerous if nobody is watching the total. But the asymmetry matters for a small business: if the estimate is wrong on a day-rate engagement, that is your problem, and you usually discover it in month three.

Why the rate tells you so little

For context, the median UK contract day rate for a Power BI consultant was £450 in the six months to 1 September 2026, with the tenth percentile at £360 and the ninetieth at £508 (IT Jobs Watch). Treat that as directional — it is drawn from a thin sample of advertised contract roles, and advertised contract rates are not consultancy quotes.

Here is the arithmetic that matters. Two suppliers quote for the same first data model:

• Supplier A: £400/day, estimates 25 days → £10,000
• Supplier B: £600/day, estimates 12 days → £7,200

Supplier B is 50% more expensive per day and 28% cheaper overall. Experience shows up in the day count, not the rate, and the day count is the number nobody puts in the headline. Someone who has built the same star schema twenty times does it in fewer days than someone learning on your budget — and leaves behind a model the next person can read.

This is why a rate comparison between two quotes is close to meaningless, and why we publish planning day bands per scope rather than a rate card. That post is the canonical one for what a whole project costs; this one is only about how the two pricing shapes behave.

The questions that reveal the real number

Ask all five of every supplier, and compare the answers rather than the prices.

"What exactly will exist at the end?" A named artefact — a semantic model over these four sources, three report pages, refresh scheduled, one handover session. If the answer is a duration rather than a deliverable, you have been quoted for attendance.

"What is explicitly not included?" The exclusions list is the single most informative part of a quote. A supplier who has done this before knows precisely what people ask for in week five, and will have written it down. A supplier with no exclusions list has not thought about scope.

"What happens when the source data turns out to be worse than we said?" It usually is. Ask whether that is a change request, absorbed, or a conversation. Any answer is fine; not having one is not.

"How many review rounds are included?" Two is normal. Unlimited is a supplier who will run out of goodwill, then patience, then care.

"Who owns the output, and can our own team maintain it?" A model only one person can read is a subscription you did not agree to.

When a day rate is genuinely the right answer

Three cases, and they are real:

Discovery. When nobody yet knows what should be built, a fixed price is either padded or wrong. Buy a short, time-boxed discovery — three to five days — and expect a scoped fixed price to come out of it.

Ongoing support. A retained half-day a month for changes, refresh failures and new questions. There is no deliverable to fix a price against, and pretending otherwise helps nobody.

A backlog you control. If you have a prioritised list and a person internally who can direct the work week by week, day rates are efficient and honest.

Outside those three, if you can describe what you want, ask for a price for it.

Two traps worth naming

"Fixed price" with no exclusions. A total with no scope statement behind it is a day-rate engagement in disguise. When the work overruns, the conversation will be about what was "obviously included", and neither side will have written it down.

Comparing quotes with different scopes. The cheapest quote is frequently the one that quietly omitted the data cleansing. Line the deliverables up side by side before you line the numbers up. If one supplier's quote is 40% below the others, the usual explanation is that they are pricing a different job.

One UK-specific note on contractors

If you engage an individual contractor on a day rate rather than a consultancy, the off-payroll working rules are worth understanding. For small private-sector clients, HMRC's rules place responsibility for determining the worker's employment status on the worker's own intermediary rather than on you (GOV.UK, understanding off-payroll working). Medium and large clients carry that responsibility themselves. It is one practical reason many SMEs prefer buying a defined deliverable from a firm over a day rate from an individual — though it should not be the deciding factor.

To sanity-check any quote against licence costs and your own user numbers, our Power BI pricing estimator models the ongoing side. The Power BI consultancy page and our wider data practice explain how we scope and price this work, and if you are earlier in the process, what a Power BI consultant actually does is the place to start.

Frequently asked questions

Is a day rate or a fixed price better for a Power BI project?

Fixed price is usually better for a first, well-defined piece of work, because it puts the estimating risk on the supplier and gives you a number you can approve. Day rates are better for genuinely open-ended work — discovery, ongoing support, a backlog with no fixed end. The mistake is using day rates for something you could have scoped.

How do I compare a day rate quote with a fixed price quote?

Convert both to a total for the same defined scope, then compare what happens when that scope changes. A day rate multiplied by an estimate is not a price — it is a forecast the supplier can revise. Ask each supplier what the deliverable is, what happens if it takes longer, and who pays for rework.

Does a higher day rate mean a more expensive project?

Not reliably. Total cost is the rate multiplied by the days, and experience mostly shows up in the second number. Someone who has built the same semantic model twenty times will do it in fewer days than someone learning on your budget, which is why comparing rates alone tells you very little.

Do IR35 rules apply when we hire a Power BI contractor?

If you are a small private-sector business, the responsibility for determining employment status sits with the worker's own intermediary rather than with you, under HMRC's off-payroll working rules. That is one practical reason many SMEs prefer engaging a consultancy on a fixed-price deliverable rather than a contractor on a day rate.

What should a fixed-price quote actually contain?

A named deliverable, a list of what is explicitly excluded, the number of review rounds included, who provides the data and by when, and what happens if the scope changes. A quote with a price and no exclusions list is not really fixed — it is a day-rate engagement wearing a disguise.

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Easy Insight is a UK consultancy for AI, web, apps and data — senior specialists only, no juniors.