Are Energy Monitors Worth It in NZ?

Smart plugs and whole-home monitors show you exactly what's chewing through power — but seeing the number isn't the same as saving money from it.

Two very different products

"Energy monitor" covers two quite different things. Smart plugs with monitoring (from brands like TP-Link Tapo and Meross) sit between an appliance and the wall socket and report how much that single device uses — typically $15–$35 each in NZ. Whole-home monitors (like Wiser Energy, Eyedro, or CT-clamp systems installed at the switchboard) track your entire house's consumption in real time, typically costing $250–$500 including installation.

What they're actually good for

Both device types are genuinely useful for identifying waste — a smart plug on a hot water cylinder or heat pump reveals exactly how much of your bill that appliance accounts for, and a whole-home monitor can flag a fridge that's quietly drawing far more than it should, or a "phantom load" from devices left on standby overnight. That diagnostic value is real and can lead to genuine behaviour changes, like adjusting a hot water cylinder's timer or replacing an inefficient old appliance sooner than you otherwise would.

Where the savings claims get oversold

The device itself doesn't save you anything — it only saves money if you act on what it shows you, and many buyers check it enthusiastically for the first few weeks and then stop looking. Realistic savings from behaviour change after installing a monitor tend to land around 3–8% of a typical power bill, according to household energy studies, not the "up to 30%" figures sometimes used in marketing. For an average NZ household paying around $220–$280 a month, that's roughly $8–$20 a month in genuine savings — meaningful, but modest against the cost of some whole-home systems.

Payback in practice

A single $20 smart plug monitoring your biggest single load (often the hot water cylinder or a heat pump) can pay for itself within a couple of months if it prompts even a small change in usage timing. A $400 whole-home monitoring system, by contrast, needs sustained savings of around $15–$20 a month just to break even within two years — achievable for a household that genuinely changes habits, but a poor investment for someone who just wants the dashboard and doesn't act on it.

Who should actually buy one

• Households with solar — a monitor makes it far easier to shift usage (laundry, dishwasher, EV charging) into daylight hours to use more of your own generation.
• Anyone suspicious of one specific appliance — a $20–$30 plug-in monitor on a hot water cylinder, heater, or old fridge answers the question cheaply.
• People who already track spending closely — if you're the type to actually look at a dashboard weekly and adjust behaviour, the whole-home option pays off faster.

If you just want a general sense of where power goes without spending anything, most NZ lines companies and retailers now offer free usage breakdowns through their app — worth checking before buying hardware at all.