Fire alarm installation is priced from the device schedule, not from the floor area, and the device schedule comes from the category. That is why two quotes for the same building can differ by half: they are quoting different systems. Fixing that before you compare prices is the single most useful thing a buyer can do.
What drives the price
The number of devices, which follows from the category. The difficulty of getting cable to them, which follows from the building. The panel, which follows from whether the system is conventional or addressable and how many loops it needs. And the interfaces, because every door holder, damper and lift recall is a cable, a module and a line in the cause and effect matrix that has to be commissioned and tested.
The lines that get left off
Making good after cable routes. Out of hours working in an occupied building. The zone plan and log book. Commissioning and the certificates. Training somebody on site to operate the panel. Handover documentation. All of those are real work and all of them appear on some quotes and not others, which is most of the apparent price difference between two firms quoting the same category.
Design before price
Get the category and the device schedule fixed, in writing, before asking for prices. Then every quote is pricing the same system and the comparison means something. If a firm proposes a different category, that is a useful conversation to have on its merits rather than something hidden inside a lower number.
Placement is a design output, not a site decision
Where each detector goes follows rules about ceiling height, obstructions, airflow, distance from walls and proximity to things that cause false alarms. Devices placed on site by eye are the most common cause of a system that works and annoys everybody. The design drawing should show positions, and the commissioning should confirm they were followed.
Questions people ask about fire alarm installation cost
Why do fire alarm quotes vary so much?
Usually because they are quoting different categories and therefore different device counts, and because commissioning, documentation and making good appear on some quotes and not others.
Should I pay for a design separately?
For anything beyond a small like for like replacement, yes. A fixed design makes quotes comparable and is normally cheaper than the spread between uncomparable ones.
What should I receive at handover?
Design, installation and commissioning certificates, the cause and effect matrix, as installed drawings, the zone plan, the log book and operating instructions. Ask for the list in the order rather than at the end.