Electrical Contract Works · Question

What does an electrical contractor need to see on the site before quoting?

Short answer

A contractor needs the architectural and structural drawings, the equipment or load list, any electrical design already prepared, and a physical visit to the site. Together these show what must be wired, where cables can run and what already exists. A quotation given without them is an assumption, and assumptions tend to reappear later as extra charges.

In more detail

A reliable quotation comes from three sources of information, and a careful contractor will ask for all of them.

Floor plans and sections show room layouts, ceiling heights and where panels and shafts can go. If an electrical designer has produced a single-line diagram or a layout, the contractor prices from that. If not, the contractor may price from a brief and flag what is assumed. Either way, the quotation should say which documents it was based on.

Machines, lighting types, air conditioning and planned future additions all shape cable and panel sizes. Without a list, the contractor guesses, and guesses are usually either too low or padded.

Drawings do not show everything. A visit lets the contractor see:

the stage of construction and whether walls, ceilings and floors are finished
the location of the incoming supply and any existing meters or panels
access for cable routes, conduits and equipment delivery
the condition of any existing wiring that will be retained or removed

Compare like with like

Give every contractor the same documents and the same visit. When quotations differ widely, the cause is usually different assumptions rather than different value, so ask each to list what is included and excluded.

Contractors may also ask who supplies items such as light fittings, who handles the supply authority application, and whether testing and documentation are included. Settling these points before the quotation avoids disagreement after work starts.

Key points

Share drawings, the equipment list and any existing electrical design with every contractor.
A site visit reveals access, existing wiring and supply details that drawings omit.
Ask each quotation to state the documents and assumptions it relies on.
Clarify who supplies fittings, handles authority applications and provides test records.
Wide gaps between quotations usually reflect different assumptions, not different quality.

Who this applies to

Owners inviting quotations for a new building or a major renovation.
Project managers comparing several electrical contractors.
Businesses planning to retain part of an existing installation.

Last reviewed 3 October 2026

This answer is general information, not advice on your particular case. Terms, eligibility, and requirements change, so check the current position with the relevant institution or authority.