Running cost is rated watts x hours used x your unit rate. At a comparison-site average of 32.49c per kWh, a chiller averaging 300 W for 6 hours a day would use about 54 kWh in a 30-day month, roughly €17.54. Those wattage and hours figures are assumptions for illustration, not specifications for any product, so replace them with your own.
The formula
Electricity is billed in kilowatt-hours (kWh). One kWh is one kilowatt (1,000 W) running for one hour. So:
- kWh = watts divided by 1,000, multiplied by hours running.
- Cost = kWh multiplied by your unit rate in cent, divided by 100 for euro.
- Add the pump or filter separately, since it often runs for more hours than the chiller.
A chiller does not draw its full rated power continuously. It cycles on and off to hold temperature, so its average draw depends on tub volume, insulation, whether there is a lid, the air temperature and how often you use the tub. A manufacturer's rated figure is the maximum; if a supplier gives a typical daily kWh, treat it as a claim to check against your meter.
Which unit rate to use
Use the rate on your own bill, including VAT, and note if you are on a day and night tariff. For a reference point, Selectra Ireland's electricity price guide, updated in October 2026, gives an average of 32.49c per kWh including VAT for a standard 24-hour urban meter, based on a comparison of supplier standard rates. That is a comparison-site average, not an official regulator figure, and individual suppliers and plans differ. Standing charges are separate and do not change with how much you use.
Rates move, so recheck before you rely on any figure. A reading of your own meter before and after a week of use is the most reliable measure of what the tub adds.
Worked example with stated assumptions
Assumptions, all invented for the example: a chiller averaging 300 W while the tub is held cold for 6 hours a day, a circulation pump of 40 W running 24 hours a day, 30 days, and a rate of 32.49c per kWh including VAT.
| Item | Calculation | kWh per month | Cost per month |
|---|---|---|---|
| Chiller | 0.3 kW x 6 h x 30 days | 54.0 | about €17.54 |
| Circulation pump | 0.04 kW x 24 h x 30 days | 28.8 | about €9.36 |
| Total | 82.8 | about €26.90 |
Change one assumption and the answer moves. If the chiller needs to work for 12 hours a day in a warm spell, that line doubles. If you switch the pump off when the tub is covered and clean, that line shrinks. Your real figures could be well above or below this example.
Heating or cooling a fresh fill
Cooling a full tub from tap temperature takes real energy. Physics sets a floor: water needs about 4.186 kilojoules to change one kilogram by one degree, and 3,600 kilojoules equals one kWh. Cooling 300 litres by 10°C therefore removes about 3.5 kWh of heat, which at 32.49c would cost about €1.13 if it were done with perfect efficiency. Real units lose some to the surroundings, so treat that as a minimum. The same sum works in reverse for warming water.
An ice-cooled tub has no chiller bill, but ice is not free: bought bags have a price that varies by retailer, and home freezing uses freezer energy. Work out how much ice you add per session and compare on the same basis.
Water and filtration
Uisce Éireann's household conservation page describes an excess usage charge for water above an annual allowance: a default of 213,000 litres per household, with charges for use above it. That page appears to describe the scheme as introduced, so check water.ie for the current position before relying on the figures. As a scale check, refilling a 400-litre tub twelve times a year uses 4,800 litres, about 2% of that allowance.
Other consumables vary by product and supplier: replacement filters, sanitiser and test strips. Look up the filter type for any model you are considering and the price of replacements before buying, since this is a cost you will pay repeatedly.
Any seller figure for running cost should state the tub volume, ambient temperature, target water temperature and hours used. Without those conditions it cannot be compared with your set-up. For the purchase decision see the cold plunge tub buyer's guide and purchase costs.
Ways to keep the bill down
- Use a fitted, insulated lid whenever the tub is not in use, so the chiller has less heat to remove.
- Site the tub in shade and out of the wind where possible; sun on the tub raises the chiller's workload.
- Set the target temperature no lower than you need. Each degree colder means more running time.
- Run the filter on a schedule that matches the manufacturer's guidance, not 24 hours by default, if the instructions allow it.
- Check whether a day and night tariff suits you if the chiller can run off-peak. Your supplier's terms decide whether this saves money overall, so compare using your own usage.
Electrical safety is part of the cost
If a chiller needs a new outdoor socket or circuit, include an electrician in your costs. ESB Networks says permanent outdoor wiring must be installed by a registered electrical contractor, and advises RCD protection and outdoor-rated equipment. This is a safety requirement, not an optional extra.
Frequently asked questions
How do I work out what my chiller costs to run?
Multiply rated kilowatts by hours running, then by your unit rate. Use the rate on your bill and remember chillers cycle on and off.
What unit rate should I use?
Your own bill's rate including VAT. Selectra's October 2026 average of 32.49c per kWh is only a reference.
Is the pump or the chiller more expensive?
It depends. A pump draws less but may run for far more hours, so calculate both separately.
Will filling the tub raise my water bill?
Uisce Éireann describes an excess usage charge above an annual allowance. Check water.ie, since the page consulted may be out of date.