Smart grids vs "intelligent power networks": what actually reached NZ homes

Around 2007, people who wrote about the future of electricity liked the phrase "intelligent power network". The picture was of a grid that thought for itself: thousands of small generators, storage devices and appliances all talking to each other, balancing supply and demand locally, and needing far less from big power stations. A Christchurch group whose work was followed by the earlier site at this address was one of many developing ideas along those lines.

Two decades on, the smart grid has arrived in New Zealand, just not quite in that form. It came in through the meter box, the hot-water cupboard and the garage, one practical device at a time.

New Zealand had a head start: ripple control

Long before anyone said "smart grid", New Zealand lines companies were switching household hot-water cylinders on and off remotely. Ripple control sends signals down the power lines to receivers in the switchboard, letting the network turn off cylinders for a while during peak demand. Hot water stays hot for hours in a well-insulated cylinder, so most households never notice.

That old system is an early example of what is now called demand flexibility: shifting when electricity is used, rather than building more capacity to meet the peak. It is still in use in many areas, and it is one reason New Zealand's winter evening peaks are more manageable than they might be.

Smart meters: the foundation

Over the 2010s, most New Zealand homes had their old spinning-disc meter swapped for a smart meter. These record use in half-hour blocks and send readings back automatically.

Smart meters made two things possible:

• No more estimated bills. Retailers bill on actual use.
• Time-of-use pricing. Because use is recorded half-hourly, retailers can charge different prices at different times of day. Many now offer cheaper off-peak power at night or in the middle of the day, and some offer a free or discounted hour or two.

For a household, time-of-use plans reward exactly the behaviour the grid needs: running flexible loads when demand is low. The Electricity Authority's consumer pages explain how to compare plans and switch retailers.

The new flexible loads: EVs and smart chargers

An electric car is the biggest new load most households will add. A typical 7 kW wall charger, while it is running, draws more power than most of the rest of the house combined. If every EV in a street started charging at 6pm on a winter evening, local networks would struggle.

The answer is the smart charger: a wall-mounted charger that can be scheduled, respond to price signals, or be managed by the retailer or lines company within limits the owner sets. Most EV owners plug in when they get home but don't need the car until the morning, so charging can happen any time overnight without the driver noticing.

Transpower's 2020 Whakamana i Te Mauri Hiko report, which looked at how New Zealand could electrify its energy use, pictured a 2035 grid supported by millions of smart appliances and smart EV chargers, alongside many small solar and battery systems. That is the intelligent power network, rebuilt from ordinary household devices.

Solar, batteries and the two-way grid

Rooftop solar and home batteries make the household a generator as well as a customer. Modern inverters can respond automatically to network conditions, for example by reducing export when local voltage rises. Some retailers and aggregators pay households to let them use their batteries at peak times.

This is the part of the 2007 vision that is closest to arriving in full, though it is still early. Research groups such as the University of Canterbury's Electric Power Engineering Centre study how networks cope as more small generators and flexible loads connect. See our piece on distributed generation for the household side.

What a household can do now

You don't need to wait for the full smart grid to benefit from it:

1. Check your plan. If you have a smart meter (most homes do), look at whether a time-of-use plan would suit your pattern of use.
2. Time the hot water. If your cylinder is not on ripple control, a timer or smart controller can heat it in cheaper hours.
3. Choose a smart EV charger. If you are installing a home charger, a scheduled or smart model lets you charge off-peak automatically. Installation is a job for a licensed electrician.
4. Shift the big appliances. Dishwashers, washing machines and dryers often have delay timers. Use them.
5. Keep heating steady. Heat pumps run most efficiently when they hold a steady temperature, rather than working flat out at peak times.

The verdict

The intelligent power network of 2007 imagined a grid redesigned from the ground up. What happened instead was incremental: smart meters, new tariffs, smarter chargers and inverters, layered on top of a grid that already had some clever tricks. It is less visionary, but it works, and it is still growing.

More in the energy section.