How much does a spa pool cost to run in NZ?

Roughly $133 a month, or about $1,590 a year, for a typical well-covered spa held at 38°C. That makes it the largest single appliance load in most houses that have one - ahead of heating, hot water and everything in the kitchen combined. A spa with a tired cover on an exposed site can easily reach $3,181 a year.

Does a spa pool cost more to run in winter?

Substantially, and for the obvious reason: the difference between 38°C water and the outside air is far larger in July than in January, so heat leaves faster and the element runs more to replace it. Wind matters as much as temperature - an exposed site loses heat much faster than a sheltered one at the same air temperature. Expect winter months to run well above the annual average and summer months well below.

Is it cheaper to leave a spa on all the time or heat it when needed?

For regular use, leave it on. A spa holds a lot of water and reheating it from cold takes many hours of full-power element time, so switching it off between weekly soaks usually costs more than maintaining temperature. The calculation flips if you genuinely go months without using it - then a full shutdown and drain is the cheaper option, and that is a different decision from switching off for a week.

What is the single best way to cut spa pool running costs?

The cover. Nearly all of the running cost is replacing heat that escapes the water surface, and the cover is what stands between the two. Covers absorb water over time, get heavy, compress their foam and stop sealing at the edges - at which point they look fine and insulate poorly. Replacing a tired cover can be worth several hundred dollars a year, and on the figures here the gap between a good cover and a poor one is about $2,386 annually.

Running cost

What a spa pool actually costs to run in NZ

By Jason Webb· Published 6 August 2026· Updated 6 August 2026· 8 min read

If you own a spa pool, it is almost certainly the most expensive thing on your power bill. Not the most expensive appliance - the most expensive anything. At roughly $1,590 a year it sits at the top of our table of all 45 household appliances, ahead of whole-house heating and well ahead of hot water.

The useful thing to understand is what that money is buying, because it is not what most people assume.

You are not paying to heat the water

Heating a spa from cold is a one-off cost, and it is not the big number. The recurring cost is standing heat loss - the water is sitting at 38°C in air that is considerably cooler, and physics is continuously moving heat from the first to the second. The element's job is to replace that, forever, whether anyone gets in or not.

This is why bathing habits barely register in the running cost, and why the things that do move it are all about slowing that loss down:

Annual running cost of the same 4.0 kW spa in different conditions, at 36.3c/kWh
Condition	Per month	Per year
Good hard cover, 36°C, summer Little heat lost, little to replace	$66	$795
Typical - decent cover, 38°C, year-round The default assumption on this site	$133	$1,590
Tired cover or 40°C setpoint A waterlogged cover is the usual culprit	$199	$2,386
Poor cover, exposed site, winter Wind across an uncovered surface	$265	$3,181

Same spa, same water, same household - and about $2,386 a year between the top row and the bottom. None of that difference is about how often you use it.

The cover is the whole game

A spa cover is not a lid to keep leaves out. It is the insulation, and it is the single component that decides your running cost.

Covers fail slowly and invisibly. The foam core absorbs water over a few years, which makes the cover heavy - often the first thing owners notice - and water conducts heat far better than the trapped air it replaced. At the same time the foam compresses and the edges stop sealing. A cover in this state looks perfectly serviceable and insulates like a tarpaulin.

Lift test. If the cover has become noticeably heavier than when it was new, it is waterlogged and it is costing you money every day.
Edge seal. Steam escaping around the perimeter on a cold morning is heat leaving. The skirt should sit flush.
Add a floating blanket. A thin thermal blanket sitting directly on the water surface under the hard cover cuts evaporation, which is a large share of the loss.
Replace it when it fails. A new cover is a few hundred dollars against a difference of $2,386 a year at the extremes.

Two degrees is worth real money

Heat loss scales with the gap between the water and the air, so the setpoint has a direct and continuous effect. Dropping from 40°C to 38°C reduces that gap by a meaningful fraction on a cold night - and 38°C is still hot enough that most people cannot tell the difference once they are in.

Turning the spa down between uses, rather than off, is the version of this that works for regular users: hold it a few degrees lower through the week and bring it up for the evening you plan to use it.

Shutting down out of season

The one thing that genuinely eliminates the cost is not running the spa. Most New Zealand households use theirs far more in winter than in summer, which is unfortunate - winter is when it costs most - but it does mean there is often a stretch of warm months where the spa is heated and unused.

A full shutdown for 4 summer months saves around $530. That is a proper drain, clean and power-down, not just switching it off - a spa left full and cold grows things. It is a couple of hours' work at each end.

Do not confuse this with switching off between weekly soaks, which is usually a false economy: reheating that volume of water from cold takes many hours of full-element running, and typically costs more than holding temperature would have.

The other levers

Shelter it. Wind strips heat off a cover far faster than still air at the same temperature. A fence or a wall on the prevailing-wind side is a permanent, no-running-cost improvement.
Check the cabinet insulation. Cheaper spas often insulate the shell and leave the cabinet cavity essentially open. Filling it makes a real difference on an older unit.
Run the filtration cycle at night if you are on a day/night plan - the pump is a small part of the total, but it is the part you can freely reschedule. Our guide on when power is cheapest covers whether your plan rewards this.
Fix leaks immediately. Water lost is heat lost, and it is replaced with cold water that must be heated from scratch.

To model your own spa against your own rate, open the calculator - adjusting the hours per day is the way to represent a better or worse cover. Our longer guide on spa pool running costs goes further into buying decisions and insulation grades.