Why nobody will quote you for AV installation

So the useful question is not what AV installation costs. It is which of these you are actually asking about, because the answer changes by a factor of fifty between the first and the last.

What the phrase is doing the work of

One screen, one source, one room

A television on the wall, a soundbar under it, a streaming box behind it and the cables hidden. An afternoon, one technician, no trades involved. This is the overwhelming majority of what people mean when they type the phrase, and it is the cheapest thing on this list by a wide margin.

One room, done properly

The same room with separate amplification, five or seven speakers, a subwoofer positioned rather than dropped in a corner, and the whole thing calibrated to the room instead of left on the factory preset. More hardware, and considerably more time, because most of the work is speaker placement and measurement rather than mounting.

A dedicated room

A projector, a screen, treated acoustics, tiered seating, and a rack of equipment somewhere else in the house feeding it. This is a building project with AV in it, and it involves an electrician and often a builder. Anyone quoting this from a phone call is guessing.

The whole house

Audio in several rooms, screens fed from a central rack, network and control on top of it. The cost here is dominated by cable runs and by whether the walls are open. The same system in a new build and in a finished double-brick house are different jobs with different numbers.

The three questions that decide your number

Whichever tier you are in, the same three things move the figure more than the brand of anything.

Are the walls open?

This is the big one and it is binary. Cable run before the plasterboard goes on is quick and invisible. The same cable in a finished house has to find a path through a roof cavity, down a wall that may be double brick, around a fire collar and past whatever the last renovation left in the way. If you are building or renovating, the cheapest AV work you will ever buy is the cabling you put in before the walls close.

How many rooms have to talk to each other?

One room is one system. Two rooms that need to show the same thing is a distribution problem, and distribution is where the cost stops being about speakers and starts being about infrastructure. The jump from one room to two is much larger than the jump from two to three.

Does it have to be invisible?

Concealment is labour, not hardware. In-wall and in-ceiling speakers, a screen with no visible cable, equipment in a cupboard in another room: each of those is a decision that adds hours rather than parts. It is a legitimate thing to want and it is worth knowing it is the part you are paying for.

How to get a number that means something

Describe the end state rather than the equipment. Not "how much to install a home theatre", but "a 75-inch screen on the brick wall in an open-plan living room, sound that works for films and for television, nothing visible, and it has to be simple enough that my parents can use it". That paragraph can be quoted. The word "AV" cannot.

It is also worth saying what you do not want, because it is usually the faster half of the conversation. Most people who ask about home cinema do not want a dedicated room, and most people who ask about multi-room audio want two rooms rather than six. Saying so early stops you being quoted for something you were never going to buy.

For the tier most people mean by the phrase, that is home theatre and cinema room installation, quoted after a look at the room rather than from a price list.