RCD Requirements in NZ: What Homeowners Need to Know

Rudi Visser

2 days ago

10 min read

Homeowner discussing an RCD with electrician

In New Zealand, new circuits that supply lighting or socket outlets in a home must have RCD protection, normally fitted at the switchboard. Existing safe installations do not have to be upgraded. Only the parts you alter, add or relocate need to meet the current rules. This guide explains what that means for a renovation, a purchase or a repair, which type of RCD to expect, how fast it must trip, and how to test the ones you already have.

An RCD (residual current device) monitors the current flowing through a circuit. If some of it leaks to earth, for example through a person, the RCD cuts the power. It does this in milliseconds.

TL;DR

New circuits from the switchboard that supply domestic lighting or socket outlets need RCD protection, normally at the switchboard.
Existing safe wiring can stay as it is. There is no mass retrofit requirement, but altered or added parts must meet current standards.
For work starting after 12 November 2026, the cited AS/NZS 3000:2018 requires shock-protection RCDs to be Type A, F or B, not plain Type AC.
WorkSafe recommends testing switchboard RCDs every six months. Switchboard RCD work must be done by a licensed electrical worker.
If you are buying an older home, check the switchboard for RCDs and press the test button before you commit.

What the rules say about RCDs in homes
Do older homes have to be retrofitted?
What type of RCD do you need?
How fast must an RCD trip?
The three kinds of household RCD
Testing your RCDs
Who is allowed to do the work?
What first-time buyers should check
RCDs when you renovate
Our perspective
How we can help
FAQ
Sources

What the rules say about RCDs in homes

RCD installation in New Zealand is governed by the Electricity (Safety) Regulations 2010 and the version of AS/NZS 3000 that the regulations cite. WorkSafe sets this out for low voltage installations, and Standards New Zealand advises users to consult WorkSafe when they need clarity on what a requirement means in practice.

In practical terms, the rules work like this:

New circuits. All new circuits from the switchboard supplying domestic lighting or socket outlets must have RCD protection, normally at the switchboard.
Where it is not at the switchboard. The homeowner code of practice, ECP 51, says the RCD must be connected to the first socket outlet on a new wiring circuit if it is not installed at the switchboard.
Damp areas. WorkSafe recommends RCDs in damp areas that have electrical fittings: bathrooms, laundries, kitchens, garages and areas with external outlets.

The last point is a recommendation for existing homes, not an order to retrofit. The next section explains the difference.

Do older homes have to be retrofitted?

No. WorkSafe’s guidance on the recent regulation changes says that existing installations may continue and be repaired if they are not unsafe. Only the parts changed in relocations, additions or alterations need to meet the new standards.

This matters most when you renovate. Moving a kitchen, adding a bathroom or adding a heat pump circuit usually means new or altered circuits. Those circuits need RCD protection even when the rest of the house does not have it. A renovation can therefore bring a switchboard upgrade into the scope even if you did not plan one.

Two situations come up often:

A like-for-like repair. Replacing a faulty socket or a damaged cable on an existing circuit is a repair. It does not by itself trigger a full upgrade, as long as the installation is not unsafe.
An addition or alteration. A new circuit for an oven, a new set of sockets in an extension or a relocated switchboard counts as new work. It must meet the current standard.

If you are unsure which category your job falls into, ask a licensed electrician before work starts. Also see our guide to electrical consent in NZ, which covers what needs paperwork and when.

What type of RCD do you need?

RCDs come in types that differ in the fault currents they detect. A plain Type AC device detects ordinary alternating leakage. Modern appliances such as inverters, EV chargers and some heat pumps can produce pulsating or smooth DC leakage. A Type AC device may not respond properly to that.

The cited AS/NZS 3000 addresses this. WorkSafe’s update says RCDs must be selected and installed to suit the intended loads, taking into account pulsating and constant DC fault currents and waveform distortion. Shock-protection RCDs must be Type A, F or B as specified.

The date matters. WorkSafe states that new installations whose construction begins after 12 November 2026 must comply with AS/NZS 3000:2018, including Amendments 1, 2 and 3 (same WorkSafe update). In plain terms:

Situation	What to expect
Work started before 12 November 2026	Your electrician works to the standard in force when the work began. Ask which one applies.
New installation begun after 12 November 2026	AS/NZS 3000:2018 with Amendments 1, 2 and 3. Shock-protection RCDs must be Type A, F or B.
Electric vehicle charger at a home	The final subcircuit must be protected by a Type B RCD, unless a Type A RCD is combined with an RDC-DD that complies with IEC 62955.

The EV requirement comes from WorkSafe’s addendum to its EV charging guidelines. The same document says charging subcircuits at residential locations must include a means of monitoring earth connection continuity.

You do not choose the RCD type yourself. Your electrician selects it from the circuit and the loads on it. What you can do is ask which type is being installed and why, and make sure it appears in the electrical certificate paperwork.

How fast must an RCD trip?

Speed is what makes an RCD protective. The Electricity (Safety) Regulations 2010 define when a shock-protection RCD is unsafe. An RCD with a rated residual current above 30 milliamperes is electrically unsafe if it fails to interrupt within 300 milliseconds at its rated residual current, or within 40 milliseconds at five times that rated current.

For a homeowner, three points follow:

Trip time is measured with a proper test instrument. The test button on the device only confirms that the mechanism works. It does not measure how fast the device trips.
Trip time is part of formal RCD function testing. WorkSafe’s update says testing must include trip time, confirmation that the device operates as intended, and checks for DC leakage and constant DC where applicable (same WorkSafe update).
A device that does not meet these limits is a safety defect. Do not rely on it while you wait for a repair.

The three kinds of household RCD

WorkSafe lists three kinds of RCD in homes: fixed RCDs installed in standard socket outlets, circuit RCDs wired into the switchboard, and portable RCDs.

Circuit RCDs at the switchboard protect everything on the circuit: wiring, sockets, lights and what is plugged in. This is the standard for new circuits.
Socket-outlet RCDs protect what is plugged into that socket, and sometimes sockets downstream of it. They are a practical option on an older circuit where adding a switchboard device is not yet planned.
Portable RCDs plug into a socket and protect one lead or appliance. They suit outdoor power tools, a garage or any place where you cannot be sure of the supply.

A circuit RCD gives the widest protection. A portable one is a useful extra, not a substitute for a compliant switchboard on new work.

Testing your RCDs

There is no single legally fixed testing interval for household RCDs. What WorkSafe gives is a recommendation: test switchboard RCDs every six months, for example when the clocks change for daylight saving.

A simple routine:

Find the switchboard, usually in the garage, hallway or a utility cupboard.
Locate the RCD. It has a button marked T or Test.
Press the button. The device should trip and power to its circuits should cut off.
Reset it and check that the circuits come back on.

If the RCD does not trip when you press the button, do not use the circuits it protects until a licensed electrician has looked at it. If it trips repeatedly, that is the device doing its job. Unplug appliances one at a time to find the cause. A faulty appliance, moisture in an outdoor fitting or damaged cable insulation are common causes. If the cause is not obvious, call an electrician.

A periodic test with an instrument that measures trip time is a different thing from the button test. It is the one that confirms the device meets the limits above.

Who is allowed to do the work?

The rules let homeowners do some simple wiring jobs themselves, under ECP 51. The code covers specified wiring work on your own domestic installation and sets conditions for it. The same document makes the limit clear. Critical work such as installing an RCD at the switchboard must be done by a licensed electrical worker.

In practice, treat anything at the switchboard as a job for a licensed electrician. This also protects you at sale time and with insurance. Our guide on renovation insurance in NZ explains what to check before you hire.

What first-time buyers should check

A house that was legal when it was built can still have an older switchboard. Before you buy, look for these:

Is there an RCD at the switchboard? Look for a device with a test button. Ceramic fuses and no RCD indicate an older installation.
Does it trip when tested? Press the button during a viewing, with the owner’s or agent’s permission.
Which circuits are protected? Ask whether lighting and sockets share protection, and whether bathrooms, laundry and outdoor outlets are covered.
What has been altered? Ask for the paperwork on any electrical work done since the house was built. New circuits should have RCD protection.
What do you plan to change? Adding a heat pump, an EV charger or a new kitchen layout will pull those circuits under the current rules.

If you want a professional view, ask a licensed electrician to inspect the installation as part of your due diligence. Because existing safe wiring can stay, an older board is not automatically a defect. It does tell you where your budget may need to go. If the whole house is old, read our guide to NZ rewire costs and consent so you know the scale before you make an offer.

RCDs when you renovate

Renovations are where the RCD rules matter most to homeowners. Four common cases:

Kitchen. New benchtop sockets, a relocated oven circuit or a new island all count as new or altered circuits.
Bathroom. New lighting, a heated towel rail or a new extraction fan circuit will need protection. Our piece on bathroom lighting ideas that avoid rewiring shows how layout choices affect electrical scope.
Extension or garage conversion. New circuits, new RCD protection and often a switchboard review.
EV charger. A dedicated final subcircuit with the protection described above.

Build the electrical scope into the plan and the budget at the start. A switchboard that has to be upgraded halfway through is one of the more common causes of delay and extra cost in older houses.

Our perspective

Most RCD questions we hear are really scheduling questions. An owner plans a kitchen or bathroom, and the electrical side only comes up once walls are open. By then the electrician, the plumber and the plasterer all depend on each other’s timing.

We handle that by managing all licensed trades under one team and giving you one point of contact. The electrical scope, including any switchboard and RCD work, is decided before the job starts and priced in the fixed-fee quote. We also manage the consent process where the work needs it. If something unexpected shows up behind a wall, you hear it from one person, not from three.

Our advice is plain. Do not treat an RCD as an optional extra, do not do switchboard work yourself, and press the test button twice a year. If you are buying, have the switchboard looked at before you settle, not after.

— Rudi

How we can help

If your project involves new circuits, a switchboard upgrade or a full refit, we coordinate the licensed trades and the consent process with one point of contact and a fixed-fee quote. Kitchens and bathrooms are offered in Grade A, B and C packages on our pricing page, and larger jobs are covered on our full home renovation page. For small jobs, see our small jobs and repairs services.

FAQ

Are RCDs mandatory in all NZ homes?

Not in every existing home. They are required on new circuits that supply domestic lighting or socket outlets, normally at the switchboard. Existing installations that are not unsafe may continue, and only altered or added parts must meet the current standards.

What type of RCD do I need?

For shock protection, the cited AS/NZS 3000 calls for Type A, F or B as specified, and it applies to new installations whose construction begins after 12 November 2026. A home EV charger’s final subcircuit needs a Type B RCD, or a Type A RCD combined with a compliant RDC-DD. Your electrician selects the type to suit the loads.

How fast does an RCD have to trip?

An RCD with a rated residual current above 30 milliamperes is unsafe if it does not interrupt within 300 milliseconds at its rated current, or within 40 milliseconds at five times that current. Only a proper instrument test measures this. The test button does not.

How often should I test my RCD?

WorkSafe recommends testing switchboard RCDs every six months. Aligning it with the daylight saving changes makes it easy to remember. If the device does not trip, stop using those circuits and call a licensed electrician.