What does a plug-in oil column heater cost to run?

Plug-in oil column heaters are everywhere in NZ. They are cheap to buy and run silently, safe enough to leave going in a bedroom. The catch is that they are 100% resistive. Every watt becomes heat, but there is no multiplier the way a heat pump has one, so a unit of electricity buys you only a unit of heat.

At a typical 2,000-2,400W, leaving one on for an evening is an expensive way to stay warm. The wattage is doing exactly what it says, hour after hour, with none of the three-to-four-times leverage a heat pump gets from the outside air. That is the whole story of why it costs what it does.

They make sense for taking the chill off a single small room you use occasionally, like a spare bedroom or a study you sit in for an hour a day, somewhere installing a heat pump cannot be justified. Kept to short bursts in a small space, the running cost stays modest because the hours are low.

For any room you heat regularly the running cost gap is dramatic. A heat pump produces the same warmth for roughly a third of the power. If an oil heater is your main source of heat in a living area, it is almost always the biggest line on your winter bill, and the most fixable, because the fix is a one-off purchase that then saves you every evening.

If you are keeping the oil heater, a few habits help. Use its built-in thermostat rather than leaving it on full, so it cycles off once the room is warm. Shut the door to keep the heat in the room you are actually in, and set a timer so it is not running in an empty room. None of that changes the fundamental one-to-one efficiency, but it stops you paying to heat space and time you are not using.

The clearest way to see the difference is to price it out. Put the heater's wattage and your real evening hours into the calculator at your own rate, then compare it with a heat pump doing the same job. For a living area used most nights, replacing it could cut heating costs by 60-70%, and the numbers make that obvious.