The Conduction Company installs standby generators and the changeover gear behind them across Auckland. This guide covers when you need a generator changeover switch, how one works, who can install it, and what it costs to install in NZ. The estimates below are for standard installation of a generator changeover switch or a full generator setup. The Conduction Company confirms final pricing after a property assessment.
You need a generator changeover switch whenever a generator will power your house wiring, because it keeps the house off the power network while the generator runs. The Conduction Company fits one from about $450 including GST, and a full setup from about $1,700 including GST.
Do you need a generator transfer switch?
Yes, you really do need a generator transfer switch if the generator will power your house wiring, says The Conduction Company. AS/NZS 3000, the Wiring Rules, says an installation that uses a generator at household voltage must comply with AS/NZS 3010, the standard for generators (clause 7.8.2.10). AS/NZS 3010 then requires a changeover device wherever a generator is the standby supply for when the mains fails (clause 2.7.1). That device must stop the generator feeding back into the power network.
The Conduction Company's advice is never to run a house off a generator through a power point with a double-ended lead. That can put voltage back onto the network while people are working on the lines. A changeover switch, or a generator inlet and changeover, is the safe way to do it.
"You can't just connect a generator and have it running live at the same time as the grid. It causes real problems," says Jordan Statham, director of The Conduction Company. "You need that changeover switch to accurately switch between the two different supplies to ensure they never touch each other."
Jordan saw why during his apprenticeship, on a commercial job testing a generator built to run in parallel with the grid. That takes a complex system to match the generator to the grid's timing, and in testing the match was off. "It made a horrendous noise, and we had to shut it down immediately for safety's sake," he says. Jordan Statham says that kind of setup is rare, mostly heavy industry and power stations. In a house, the changeover switch keeps the two supplies apart.
How does a generator changeover switch work?
A generator changeover switch connects your house to one supply at a time, the mains or the generator, never both, says The Conduction Company. AS/NZS 3010 requires a mechanical interlock that stops the two being connected at once (clause 2.7.3). Some changeover switches also have a middle off position, so the house can be cut off from both (clause 2.7.4).
With a manual transfer switch, you flip the switch by hand. With an automatic one, the generator just picks up.
A manual changeover switch usually has three positions, says The Conduction Company: grid at the top, off in the middle, and generator at the bottom. In a power cut, Jordan Statham's order is:
- Turn off all the circuit breakers at the switchboard.
- Start the generator and let it come up to speed. Check it is showing 230 volts.
- Turn on the isolator at the generator inlet. Generator power now reaches the switchboard, but nothing runs on it yet.
- Flip the changeover switch from the grid side, through off, to the generator side.
- Turn the circuit breakers back on, one at a time.
Bringing circuits on one by one adds load to the generator gently, instead of all at once, Jordan says. You will probably hear it change pitch as it works harder. With only small loads, you can skip the breaker steps and switch the whole house across. Where the generator is not huge, some circuits, such as the oven and hob, stay on the grid supply only, so they cannot overload it. With a manual switch, The Conduction Company gives you a full run sheet to keep on site.
One Oratia home shows it in practice. The client had frequent power cuts and wanted a backup. The house has a three-phase supply, and The Conduction Company fitted a changeover switch that runs it from a single-phase generator. In a power cut, the client starts the generator and flips the switch. The generator can run for up to 12 hours straight, so it can go off overnight and back on in the morning if the power is still out.
How does an automatic changeover switch work?
An automatic changeover switch moves the house onto the generator with nobody touching it, says The Conduction Company. Generac, a generator maker, describes the sequence: when the mains power is interrupted, the generator starts and signals the switch to move the load across. When the mains comes back, it moves the load back. Jordan Statham says the power is usually back in about a minute this way, with nothing for you to do.
AS/NZS 3010 adds a wait before the return. The switch moves the house back to the mains only once the mains voltage and frequency have held at normal levels for a set period (clause 2.7.9). The standard says that delay is usually adjustable between 1 and 30 minutes, and 15 minutes is typical.
On off-grid homes, The Conduction Company fits generators with automatic start and an automatic transfer switch, as its guide to running a house on solar power only explains.
Manual or automatic changeover switch: which do you need?
It depends on whether you need the power back in seconds or are happy to walk out and flip a switch, says The Conduction Company. An automatic switch also needs a generator that can start itself. The Conduction Company can recommend automatic for any home, because you do nothing in a power cut. But an automatic transfer switch costs significantly more than a manual one, so weigh it against how often your power goes out.
"If you're having one or two power cuts a year, it's probably not worth the cost," says Jordan Statham of The Conduction Company. "You can just pop out, turn the generator on yourself."
For a home with solar and a battery, The Conduction Company sees a generator as the last piece. When the power goes off, the battery takes over first. When the battery runs low, the generator starts automatically and charges it. Jordan Statham calls it "a really ideal setup".
How much does it cost to have a transfer switch for a generator installed?
The estimates below are for standard installation of a generator changeover switch or a full generator setup. The Conduction Company confirms final pricing after a property assessment.
The Conduction Company fits a generator changeover switch from about $450 including GST, if the existing switchboard has room. If it needs a separate small board, that costs more. A full generator setup from The Conduction Company is from about $1,700 including GST. That covers an inlet on the outside wall, a lead to the generator, cabling back to the switchboard, and the changeover switch. Those are the starting prices to install a transfer switch for a generator to a house. What moves them up is which circuits you want running, whether the changeover is manual or automatic, how far the generator sits from the switchboard, and what the existing board can take.
The Conduction Company prices an automatic changeover on a fixed quote after a site assessment.
We quote on facts, not guesses
Before we give you a price, we carry out a proper assessment of your property and how you'll use the generator.
That way you know exactly what you're buying and the total cost, with no surprises.
Clear expectations from the outset, start to finish.
Can I install a generator transfer switch myself?
No. The Conduction Company strongly recommends against it, and its reading of the law is that a changeover switch is not homeowner work, because the switch goes in the switchboard. Fitting one is prescribed electrical work under the Electricity (Safety) Regulations 2010 (Schedule 1). Regulation 57 lists the only wiring work a homeowner may do on their own home. A changeover switch is not on that list, and the item that lets an owner swap fittings applies only if the work does not involve work on a switchboard.
As a hard rule, The Conduction Company does not test, certify or connect a homeowner's wiring. It may help only where finished work has left a client stuck, and that takes a thorough inspection and often rework. Doing it yourself is dangerous, and most inspectors will not sign it off.
Do I need an electrician to install a transfer switch?
Yes. Under section 74 of the Electricity Act 1992, nobody may do prescribed electrical work unless the Act authorises them, such as a registered electrician with a current practising licence. Once the work is done, the person who completed it must issue an electrical safety certificate (regulation 74A). A new changeover switch is not the replacement of an existing fitting, so it is not low-risk work (regulation 6A), and it needs a certificate of compliance as well (regulation 65). The Conduction Company installs and tests the changeover, and issues the electrical safety certificate for it.
In short
A generator changeover switch lets a generator run your house wiring by keeping the house on one supply at a time, and AS/NZS 3010 requires one wherever a generator is the standby supply. Fitting it is prescribed electrical work, so it needs an authorised electrician and a certificate, and The Conduction Company recommends against doing it yourself. The Conduction Company's own price for a changeover switch is from about $450 including GST, and for a full setup with an outside inlet and a lead, from about $1,700 including GST.
Frequently asked questions
What is the difference between a transfer switch and a changeover switch?
None in practice: both names describe the switch that moves a house between the mains and a generator. AS/NZS 3010 calls them changeover devices, and names a hand-operated one a manual transfer switch and a self-operating one an automatic transfer switch. The Conduction Company installs both kinds.
Can I run two transfer switches with one generator?
In The Conduction Company's view, yes, as long as the generator has enough power for both loads. An example is an outbuilding on one sub-board and another building on a second, each with its own transfer switch. AS/NZS 3010 provides for one or more changeover devices. It is not a common setup.
