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How does electricity get to your place?

The journey of an electron: how does electricity get to your home or business?

The journey of an electron from its place of creation to your home or business is a long and mysterious one. But we reckon it’s worth understanding because the process, and the different touchpoints along the way, contribute to the charges that make up your power bill.

Let’s take a look at the lifecycle of an electron through its various stages – generation, transmission, distribution, and retail – here in Aotearoa.

Stage 1: electricity generation

This is the process in which electricity is created – where kinetic energy (or the energy of motion) is transformed into electrical energy. How? Here in NZ, we harness things like wind, falling water or steam to spin turbines. Strong magnets in the turbines pass close to conductive wire, creating an electron movement, or electrical current, that’s then pushed out along the wire to the transformer, and into the transmission network.

In NZ, most of our electricity (87% in 2022) is generated from renewable sources like hydro, wind or geothermal activity, but we also use some fossil fuels like coal and gas. You can read more about NZ’s generation sources here.

Stage 2: transmission

Also known as the National Grid, the transmission network consists of the enormous pylons and lines that you might have noticed running through the countryside and the very large High-Voltage Direct Current (HVDC) cable that joins the North and South Islands.

The transmission network is carried by the big pylons (25,000 of them!) and lines you often see throughout the countryside. The lines connect each electricity generator (e.g. Lake Karapiro’s hydro dam) with one of the 170 substations, before branching off to the smaller distribution networks.

The HVDC cable is a biggie, able to transfer 1050 MW northwards and 750 MW southwards, and runs between the Haywards Substation in the Hutt Valley and Benmore Hydro Station in Canterbury. With more of our population in the North Island and most of our generation in the South Island, the cable mainly transfers power northwards during the day and southwards during the night (you can view which direction electricity’s being transferred, and how much, here).

All this combined makes up the national grid, which is owned by the Crown, and run by state-owned Transpower. Transpower’s role is to manage all of this infrastructure and make sure electricity is efficiently delivered throughout the country.

Stage 3: distribution

Think of this as the little bro of the larger transmission network. It feeds directly off the national grid, and is made up of the smaller power lines and power poles you see down your street. The role of the distribution network is to carry electricity from the bigger transmission network to individual homes and businesses.

Keeping the network in reliable, working order is the job of distribution (or lines) companies. There are around 29 lines companies, and each region of NZ has an allocated company; for example, Powerco in Tauranga and Westpower on the West Coast. They’re responsible for maintaining the power lines and power poles (both above and underground) in their area, and making sure the lines have enough capacity to cater for each customer. Some lines companies operate on a commercial basis, while others are proudly owned by local communities: Vector Limited, for example, is majority-owned by their Auckland-based community.

Once the electricity has made its way to the Installation Control Point (ICP), at each home or business, it then becomes the responsibility of your electricity retailer (like Flick!). If you’re signed up with an electricity retailer, then you’re accessing power from the national grid; you’re considered ‘off-grid’ if you’re not in any way tied to the grid and you rely on your own electricity generation to create your home’s power.

The future

Extreme weather events and our increasing demand for electricity means we’re facing more and more issues with grid reliability, capacity and affordability. The national grid itself is aging, built between the 1950s and 1970s.

As NZ faces more extreme weather events, increased electricity demand and new technologies are introduced, the infrastructure will need some serious upgrading, so Transpower is proposing a $4.7b project that will upgrade and replace ageing assets over the next 10-15 years to keep those electrons reliably flowing, and prepare for a net zero carbon future.