Where is Cosine based and what areas do you cover?

Cosine Electrical is based at Waerenga in the North Waikato, between Te Kauwhata and Morrinsville. We cover the wider Waikato and South Auckland — from Manukau down to Te Awamutu, east to Thames, west to Raglan. Drive times from Waerenga: Hamilton 30-40 minutes, Cambridge 40 minutes, Pukekohe 30 minutes, Manukau 45 minutes, Raglan 75 minutes, Thames 60 minutes.

What is the digger operator on the crew thing?

Most electricians sub-contract digging for underground work — second contractor, second quote, second site visit. Cosine has a skilled digger operator on the crew, so for underground jobs we trench our own runs. One quote, one team, one site visit. Note: Cosine is not a registered drainlayer. Wastewater and stormwater scope sits with a licensed drainlayer.

How quickly do you get back with a quote?

Within 24 hours of the site visit. Itemised, in writing, valid 30 days. For smaller jobs we can often give a rough indication over the phone if you text photos of the existing setup.

What does a switchboard upgrade cost?

A straight switchboard upgrade in an average three-bedroom Waikato house is typically $1,500-$2,500 plus GST for board and labour. Push-ups: old cable failing insulation tests, mains upgrade needed (lines company involvement), asbestos in the meter-box backing board common in 60s and 70s houses. Everything flagged in the written quote — no surprises on the invoice.

What does an EV charger install cost?

Standard install with the existing switchboard up to spec is $1,200-$1,800 plus GST plus the charger. Older home needing a board upgrade adds $1,500-$2,500. Long trenched runs to a detached garage on a lifestyle block typically $2,500-$4,500 all-in.

Do you do compliance testing for landlords?

Yes — landlord WOF-equivalent inspections, RCD function tests, written reports with photos and plain-English findings. Insurance-ready paperwork.

Do you work with builders on renovations?

Yes — preferred sparky for several builders across Hamilton, Cambridge and Pukekohe. We walk through with the homeowner and builder before quoting, mark up the plans, and work to the builder's schedule. We don't hold up the next trade.

Can you handle commercial maintenance for property managers?

Yes — scheduled maintenance contracts, emergency callouts, fault-finding, compliance reporting. One number, one paperwork system, no padded packages and no lock-ins.

Do you certify the work?

Always. Every new circuit and every board upgrade gets a Certificate of Compliance emailed through within a day of the job finishing. Required for insurance, future sale and any audit.

What if you cannot fix a fault in one visit?

Some faults like earth leakage on a circuit shared by multiple cables genuinely need a second visit. Day 1 we isolate the faulty section onto its own RCBO so the rest of the house keeps power. Day 2 we test and replace the bad section. We don't punch holes in walls to brute-force the search.

CoC, ESC and RoI: Which Electrical Certificate You Actually Need

Kris Goff

1 day ago

3 min read

Short answer: in New Zealand, a Certificate of Compliance (CoC) says the electrical work meets the standard. An Electrical Safety Certificate (ESC) says it is safe to connect and use. A Record of Inspection (RoI) says an independent inspector has checked work classed as high risk. Most domestic jobs produce a CoC and, where it applies, an ESC.

These get muddled constantly - including by people selling houses. Here is what each one is for.

Certificate of Compliance (CoC)

Issued by the electrical worker who did the job. It identifies the work, the address, the standard it was done to, and who is responsible for it. It is the core document under the Electricity (Safety) Regulations 2010, and it has to be issued for prescribed electrical work.

You should receive it without asking. If you had work done and never got one, ask for it - the electrician is required to supply it, and you will want it when you sell or claim.

Electrical Safety Certificate (ESC)

Confirms that the installation has been tested and is safe to connect to the supply. On a lot of jobs the CoC and ESC come from the same person on the same visit. On new connections it is the document the lines company and the retailer care about before the meter goes live.

Record of Inspection (RoI)

Some work is classed as high risk and has to be inspected by someone other than the person who did it. Mains work and certain new installations are the common domestic examples. The inspector issues an RoI. It sits alongside the CoC, it does not replace it.

Periodic verification - the commercial one

Different animal. Periodic verification is the scheduled re-testing of an existing installation in a commercial or industrial building, and in some residential settings. It confirms the installation is still safe years after it was signed off. Insurers, landlords and franchise agreements are the usual reason people book it, and the interval depends on the type of installation and how hard it works. There is more on our compliance testing page.

What to keep, and for how long

Keep every CoC, ESC and RoI for the life of the installation. Scan them.
Hand them over at sale. A buyer's lawyer asking about a switchboard upgrade with no paperwork is a delay you do not need.
Give a copy to your insurer after any significant work. It is the cheapest insurance conversation you will ever have.
Landlords: keep them with the tenancy file alongside your smoke alarm records.

Questions we get asked

Do I get a certificate for a single power point?

Adding a new socket outlet is prescribed electrical work, so yes - it gets certified. Swapping a like-for-like fitting generally does not.

The previous owner had work done with no paperwork. What now?

You cannot retrospectively issue a certificate for someone else's work. What you can do is have the installation inspected and tested now, and get a report on its current condition. That is usually what a buyer or an insurer actually wants.

Can a handyman do small electrical jobs?

No. Prescribed electrical work has to be done by a registered person. There is a narrow list of things a homeowner may do on their own home, and it does not include anything inside the switchboard.

How do I check my electrician is registered?

The Electrical Workers Registration Board keeps a public register. Ours is EWRB 187654.

If you need work certified

We cover the Waikato and South Auckland from Waerenga - testing, certification and periodic verification for homes, rentals and commercial premises. Call Kris on 021 466 666, or see the compliance page.