Hourly rate or fixed price? How to choose the right billing model

The debate about hourly rates versus fixed prices really comes down to one thing: risk. When you bill by time, the customer pays for the hours the job actually takes - and therefore carries the risk if it overruns. With a fixed price, you are the one who promised a number, and you are the one who pays if reality refuses to cooperate. Neither model is best in every situation. The skill lies in choosing correctly from job to job - and in setting up the agreement properly, whichever you choose.

The advantage of billing by time is simple: you get paid for the hours you spend. Hidden damage, changing requests along the way and awkward access cost the customer, not you. That makes the model ideal for repairs, fault-finding, renovation of older properties and any job where the scope only reveals itself once you are under way. The downside is that the customer does not know the final bill in advance. That creates uncertainty, can lead to disputes about hours afterwards - and it demands ongoing documentation from you: timesheets, photos and short status updates, so the bill never comes as a surprise.

With a fixed quote, the customer knows exactly what the job costs, and you know exactly what you will take in. That makes it easier to win the job, and it rewards you for working efficiently: if you finish faster than calculated, the gain is yours. In return, you carry the entire risk. If you have miscalculated, forgotten a line item or hit hidden conditions, you pay the difference yourself. A fixed price therefore requires two things: a thorough calculation based on your actual cost prices, and a clear written definition of what the price covers - and, just as importantly, what it does not.

Most private customers prefer a fixed price. It is rarely about distrust, but about budget: a family getting a new bathroom wants to know whether the bill will be 80,000 or 120,000 kroner before they say yes. Business customers and regular partners are often more comfortable with billing by time, because the relationship and track record make the hours predictable. You can use this actively: offer a fixed price on what can be clearly defined, and be honest about why the rest must run by time. A customer who understands why is far easier to work with than one who has simply been told 'I cannot say in advance'.

Here is how badly it can go when a fixed quote makes no reservations for hidden conditions. All amounts exclude VAT:

• Fixed price for a bathroom renovation: 85,000 kr
• Calculation: 60 hours at 550 kr = 33,000 kr in labour
• Materials: 40,000 kr
• Planned contribution margin: 85,000 - 33,000 - 40,000 = 12,000 kr
• Hidden under the floor is rot damage: 15 extra hours (15 x 550 kr = 8,250 kr) and 6,000 kr in extra materials
• Total extra costs: 8,250 + 6,000 = 14,250 kr - more than your entire contribution margin
• Result: 85,000 - 33,000 - 40,000 - 14,250 = a loss of 2,250 kr

One hidden defect turned a sensible contribution margin into a loss - and you still spent 75 hours on the job. With a written reservation for hidden conditions, the 14,250 kr would instead have become extra work billed by time, agreed with the customer before the repair. The reservation costs nothing to write in. It is the insurance you only miss once the damage is done.

In practice, the best agreements are often a combination:

• Fixed price with reservations: a fixed price on the visible, calculable work, with written reservations for hidden conditions such as rot, mould and non-compliant installations
• Time billing with a cap: the customer pays for hours spent, but never more than an agreed maximum - certainty for the customer, documentation duties for you
• Fixed price per stage: split the job up, so you only quote a fixed price on what you can genuinely inspect and calculate
• Fixed price on the main job, an agreed hourly rate on all extra work - and a firm rule that extra work is always approved in writing before it is carried out

The rule of thumb is simple: fixed price when you can see and calculate the job. Time billing when the scope is uncertain. Hybrid when the job is both. What matters is that the choice is deliberate and the agreement is in writing - with clear scope, reservations and an agreed procedure for extra work. If you are quoting a fixed price, everything stands or falls with the calculation: describe the job thoroughly, and use a tool like Calco to build the quote on your own hourly rates and material prices, so the fixed price rests on numbers rather than hope.