Room Heat Pump Sizing Calculator

Choosing the right size heat pump is the difference between a warm, cheap-to-run room and a unit that either struggles on the coldest days or costs more than it needed to. This New Zealand calculator estimates the heating capacity, in kilowatts, that your room actually needs, then suggests a common model size to match. Get it right and the heat pump holds your target temperature comfortably through a frosty Canterbury or Central Otago morning while sipping power; get it wrong and you either shiver or overspend. Sizing comes down to how much heat the room loses, which depends mostly on its volume, how well it is insulated, and how cold your part of the country gets. You enter the room's length, width and stud height, pick an insulation level from poor to well insulated, choose your climate zone from the warm north to the cold south, and flag whether the room has a lot of glass or exposed walls. The calculator turns that into a heating load in watts using widely used watts-per-cubic-metre rules of thumb, adjusts for your climate and exposure, and converts it to kilowatts. It then rounds up to the nearest standard heat pump capacity, the kind of figure you will see on a high-wall unit, so you can shortlist models with confidence or sense-check an installer's quote. Insulation makes a large difference, so it is worth seeing how much smaller a unit you could fit by improving ceiling and underfloor insulation first. This is a planning estimate to guide your choice, not a substitute for a professional heat-loss assessment, and you should confirm sizing with a qualified installer before buying.

A planning estimate from watts-per-cubic-metre rules of thumb, adjusted for climate and exposure, rounded up to a common model size. Heating capacity, not cooling. Confirm with a qualified installer and a heat-loss assessment before buying.