Ripple Control and Controlled Hot Water on Orion's Network

Quick answerRipple control is a signal Orion sends through the power lines to switch hot water cylinders off for short periods when the network is busiest. Orion's target is no more than 4 hours off in any 8 hour period, control periods only happen between 1 May and 31 August, and load is managed on about 50 days a year. In return, controlled hot water is priced lower.

Electrician checking a meter board and hot water relay in a Christchurch home

If your shower runs lukewarm on a freezing July morning, or your power bill shows a separate controlled rate, ripple control is probably part of the story. It works quietly in the background, and most people only notice it when something goes wrong.

This guide explains how the signal works, why Orion uses it, how to tell whether your cylinder is on a controlled rate and whether that saves you money. It also covers the wiring at your meter board that makes it work, and what to check when the hot water keeps running out.

What is ripple control?

Ripple control is a way for the lines company to switch selected appliances on and off by sending a signal down the ordinary power lines. Orion describes it as a ripple signalling system that sends signals through the network to ripple receivers, which switch appliances such as hot water cylinders on and off.

The receiver is a small relay, usually on or near your meter board. When it picks up the signal for its channel, it opens a contact that cuts power to the cylinder's element. When the signal ends, the element comes back on and the cylinder reheats. Nothing changes at your taps; the cylinder just stops adding new heat for a while.

Orion also uses ripple signals to tell major customers when a high price period is on, so they can turn off boilers or freezers or run generators. In a grid emergency, an upper South Island scheme can shed household hot water load across the region quickly to help avoid wider outages.

Why are hot water cylinders switched off at peak times?

Because heating water is one of the biggest loads in a home and it can wait a few hours without anyone noticing. Orion says its rush hours are very cold winter mornings and evenings, when heaters, ovens and showers all run at once. Delaying cylinder reheating flattens that peak, so the network does not have to be built around the single busiest hour of the year.

In Orion's words, it does not want people to run out of hot water; it just wants to delay reheating by a few hours until peak use passes. Control periods start when load is forecast to peak, last at least a complete half hour, and can only happen between 1 May and 31 August. Orion publishes a load management dashboard that shows whether a control period is on.

Christchurch frost is why this is a winter story. With about 80 ground frost days a year, and Clean Air rules limiting which wood burners can be used, the coldest mornings are when electric demand on the network is highest.

Orion hot water control	What Orion says
When control can happen	Only between 1 May and 31 August
How often	Load is managed on about 50 days a year
Longest time off	Target of no more than 4 hours in any 8 hour period
Shortest control period	At least a complete half hour
Night rate heating	Used year round to heat water overnight, unchanged in winter
Taking part	Optional; you opt in or out through your retailer

Will I run out of hot water on a cold morning?

Usually not, as long as the cylinder is the right size and working properly. Water that is already hot stays hot during a control period, and Orion says most control periods are brief. On the coldest days it may use the full four hour allowance, and that is when a small or tired cylinder shows its limits.

Running out on a cold morning is more often a cylinder problem than a ripple problem. A failed element or thermostat, a cylinder too small for the household, or a night-only plan that cannot reheat during the day are all common reasons. Back-to-back showers after a long control period can also empty a smaller cylinder.

If the water is cold all day, not just in the morning, the element may have no power at all. A relay stuck in the off position, or a tripped breaker or RCD on the hot water circuit, stops heating completely. That calls for hot water fault finding by an electrician before you call a plumber about the cylinder.

No hot water, or not enough?

Cheeky's Electrical tests the element, thermostat, ripple relay and circuit, so you know whether the fault is electrical before anything is replaced.

0800 432 532 Book Online Get a quote

How do I know if my cylinder is on a controlled rate?

Check your power bill and your meter board. A controlled rate shows on the bill as a separate line with its own price and its own kWh usage, often labelled controlled, uncontrolled, day or night. If all your power is on a single line, your hot water is probably on an uncontrolled plan.

On the bill: look for two or more meter registers or rate lines, such as uncontrolled and controlled.
On the meter board: look for a separate relay or receiver, and a breaker or fuse labelled hot water or HWC.
With your retailer: ask which plan your cylinder is on. Orion says customers opt in or out through their retailer.
With a smart meter: the control relay may be built into the meter itself, so there may be no separate box to see.

Does a controlled rate actually save money?

It can, because controlled hot water is priced lower than uncontrolled power. Orion says it encourages off-peak use through lower pricing, and that plans giving more water heating or uninterrupted water heating cost a little more. Whether you save depends on the gap between the two prices on your plan and how much of your power goes on hot water.

Compare the controlled and uncontrolled rates on your bill, then look at how many kWh the controlled line uses in a month. Multiply that usage by the price difference and you have your monthly saving. If the gap is small and you keep running short of hot water, an uncontrolled plan or a larger cylinder may be the better trade.

Night-only plans are a different deal. The cylinder heats overnight only, which suits a large, well insulated cylinder but can leave a small one short by the evening.

Can ripple control work with solar or a hot water heat pump?

Yes, but the wiring needs thought. With solar, heating water in the middle of the day with your own power is often worth more than a cheaper controlled rate at night, and a timer or diverter can make that happen. A hot water heat pump has its own controls, so check the manufacturer's instructions before putting one on a controlled circuit.

Any change to which relay, timer or meter register feeds the cylinder is work at the meter board, and your retailer may need to update the meter configuration. Older boards with handwritten or missing labels are worth tidying while that switchboard work is being done, so the next person can find the hot water circuit quickly.

When should you call an electrician about controlled hot water?

Call an electrician when the hot water stops heating altogether, the cylinder circuit keeps tripping, the relay or meter board shows scorch marks, or you want to change how the cylinder is controlled. Cheeky's Electrical tests the element, thermostat, relay and circuit, and tells you whether the fix is electrical or a plumbing job before you pay the wrong trade.

We work across the Orion network, from older homes in Papanui and St Albans to new builds in Halswell, and north of the river in Rangiora and Kaiapoi. There MainPower, not Orion, runs the lines, so ask your retailer how your cylinder is controlled.

The short answer: ripple control delays hot water reheating for short spells on cold winter days in exchange for a lower price. If you keep running short, check the cylinder and its wiring first. Book online and we will trace the cause.

Frequently Asked Questions

Does ripple control switch off my heat pump?

Orion's household control is aimed at hot water cylinders. A heat pump used for space heating is normally on an ordinary uncontrolled circuit. If yours switches off at set times every winter morning, it may have been wired to a controlled channel, and an electrician can check and change the wiring.

Can I override ripple control when I need hot water now?

Not through Orion. Some homes have a boost switch that bypasses the relay so the cylinder heats straight away, with that power billed at the uncontrolled rate. Fitting one is switchboard work for a licensed electrician, and your retailer should know about it so the metering stays correct.

Why does my cylinder switch on overnight?

Orion says night rate water heating runs year round, switching cylinders on overnight so they reheat when the network is quiet. That is separate from the winter peak control periods, which can only happen between 1 May and 31 August and are triggered when load is forecast to peak.

Is ripple control the same as a power cut?

No. Only appliances wired to the controlled channel switch off, and the rest of the house stays on. If your lights and sockets are off as well, it is an outage or a tripped main switch, not ripple control, and you should check the switchboard and the lines company's outage information.

What happens to ripple control if I get a new meter?

Some smart meters receive the control signal themselves, so a separate relay may no longer be needed when the meter is changed. Your retailer arranges the meter. If your hot water stops heating after a meter change, contact the retailer first, since the controlled register may not have been set up.