The cost to rewire an old house can’t be estimated reliably from floor area alone. The age and condition of the wiring, how easily an electrician can reach it, the number of outlets and lights you want, and the state of the switchboard all affect the scope. In New Zealand, a useful budget starts with an on-site assessment and a written quote that spells out what is included, what may cost extra, and whether GST is included. Compare quotes for the same work, not just the headline total, and allow for possible wall repairs and other work that may be needed once existing wiring is exposed.
Rewiring involves more than replacing cable. The electrician needs to assess the existing installation, plan circuits, install and connect wiring and fittings, test the completed work, and identify any related issues that affect safety or capacity. The amount of access work and finishing required can be as significant to the budget as the electrical work itself.
| Cost factor | Why it matters | What to clarify |
|---|---|---|
| Access to wiring | Accessible roof spaces, underfloor areas and wall cavities can make cable routes easier to reach. Tight, obstructed or finished spaces may require more labour or additional access work. | Will walls, ceilings or floors need to be opened, and who will repair them? |
| Condition of existing wiring | Worn, damaged or altered wiring may need more extensive replacement or investigation than expected from a visual inspection. | Does the quote cover a full rewire, or only the circuits identified so far? |
| Switchboard and protection | The existing switchboard may need changes if it is unsuitable for the new circuits or the home’s requirements. | Is switchboard work included, and what would trigger an additional upgrade? |
| Number and position of fittings | More outlets, switches, lights and dedicated circuits mean more materials and installation time. | Does the price use an agreed room-by-room list of fittings? |
| Finishes and access arrangements | Removing or protecting finishes, working around furniture, and repairing surfaces can add work beyond the wiring installation. | Are patching, painting, rubbish removal and furniture moving excluded? |
| Unexpected conditions | Hidden damage, inaccessible routes or other work discovered after opening a cavity can change the scope. | How will the electrician price and approve variations? |
These factors interact. A house with many outlets may still be relatively straightforward to wire if the routes are accessible, while a smaller home with difficult access and deteriorated wiring can require substantial labour. Ask the electrician to explain which conditions they have confirmed and which remain uncertain.
A full rewire replaces wiring throughout the agreed areas of the home. It may be considered when wiring problems are widespread, when previous alterations have left the installation difficult to assess, or when a major renovation makes access practical. It can also let you plan outlet locations and circuits for how you use the house now. Whether it is necessary depends on the installation’s condition and an electrician’s assessment, not simply the home’s age.
A partial rewire replaces or alters specific circuits or areas. It may suit a defined renovation or a localised fault if the remaining installation is assessed as appropriate to retain. It can cost less initially, but it may leave older wiring elsewhere and lead to another round of access and finishing work later. Ask the electrician to explain the risks and limitations of retaining any existing wiring.
Do not compare a quote for a partial replacement with one for a full rewire as if they were competing prices for the same job. Ask each electrician to state which circuits and rooms are included, what existing components will remain, and whether the proposed scope addresses the issues found during inspection.
Not every rewire requires a new switchboard, but the board should be assessed as part of the project. Its condition, available capacity and ability to accommodate the proposed circuits and protection are relevant. If the house needs new circuits for appliances, heating, a workshop or future EV charging, discuss those needs before the quote is finalised rather than treating them as a last-minute addition.
Ask for the switchboard work to be priced as a separate, clearly described item if it is not part of the base quote. Find out what is being replaced, what will be retained, and whether the quoted work includes testing and labelling. If an upgrade is only a possibility pending further investigation, ask for the likely scope and the process for approving it before extra work begins.
Wiring may be routed through ceiling spaces, beneath floors or inside walls, but the available route depends on the house’s construction and later alterations. A clear cavity can make installation simpler. Insulation, blocked spaces, unusual framing or surfaces that are difficult to remove and restore can add time. An electrician may also recommend a surface-mounted option in some situations; discuss how it will look and whether it suits the rooms before deciding.
Electrical work and building repairs are often separate parts of the project. A quote may include cutting access holes but exclude plasterboard replacement, plastering, painting, flooring or reinstating decorative features. If the home has older materials that could contain asbestos, don’t cut, drill or disturb them yourself. Ask how the electrician will handle suspected hazardous materials and whether a specialist assessment is needed before work proceeds.
For a house that will remain occupied, confirm how rooms and services will be affected during the job. Moving furniture, protecting belongings, temporary loss of power and arranging access can all affect the practical plan, even if they are not listed as separate costs. If the house is being renovated, coordinating rewiring with other trades may reduce duplicated access and repair work, but the sequence should be agreed in advance.
Get written quotes based on a site visit and a shared scope wherever possible. A low figure can reflect fewer fittings, excluded repairs or a partial replacement rather than a more efficient way of doing identical work. In New Zealand, make sure the quote identifies the currency and whether GST is included so the totals can be compared consistently.
Check whether each quote identifies:
Ask the electrician to separate confirmed work from provisional items. If two quotes differ substantially, ask each contractor to explain the difference against the same room-by-room scope. Check that the person or business carrying out the electrical work is appropriately licensed in New Zealand; the Electrical Workers Registration Board (EWRB) provides a way to check an electrical worker’s registration. Avoid choosing on price alone if the scope, qualifications or handover arrangements are unclear.
Start with the electrical work that addresses identified safety concerns, then decide which improvements you want included while access is available. Make a list of current problems, such as unreliable outlets or rooms with too few connection points, and a separate list of future needs. That helps the electrician distinguish necessary work from optional additions without assuming every possible upgrade belongs in the project.
Before work starts, agree on how changes will be authorised. If concealed damage or an unexpected wiring route is found, ask for a description of the issue, the proposed fix and its additional cost before approving the change. This keeps decisions visible and helps prevent optional improvements from being mixed up with essential repairs.
Photos and plans can help an electrician understand the layout, but they usually cannot show the condition and accessibility of concealed wiring. A site assessment is the better basis for a detailed quote. If an initial estimate is based on limited information, ask which parts may change after inspection.
No. The access required depends on the house’s construction, existing cavities and proposed cable routes. Ask the electrician how they intend to reach the wiring and which surfaces may need to be opened; confirm who is responsible for repairs.
It depends on the work area, the project sequence and how power will be managed. Ask the electrician which rooms and services may be unavailable and whether working in stages is practical. Make arrangements for occupants and essential equipment before the start date.
It is sensible to discuss likely needs before work begins, because outlet positions and circuit requirements affect the agreed scope. Consider how you use each room and any planned appliances, then ask the electrician what is suitable for the installation. Each addition can change the quote, so approve a revised scope in writing.
Ask the electrician which electrical certificates and records apply to the work and make sure you receive the required documents at handover. In New Zealand, these may include a Certificate of Compliance and an Electrical Safety Certificate, depending on the work. Keep the records with the home’s maintenance documents.
The most dependable way to budget for the cost to rewire an old house is to obtain a site-based quote with a clear scope, explicit exclusions and a written process for variations. Compare like for like, include the cost of making good the finishes, and settle any uncertain access or switchboard work before the project begins.
