"What will this machine cost me per month to run?" is the question most quotations fail to answer. Suppliers publish a rated wattage, a daily output and sometimes a refrigerant, but rarely a running cost, because the honest answer depends on the buyer's tariff, duty cycle and water supply. The method below lets you produce that number yourself, from published figures, in about ten minutes — and check it later with a meter.
The principle: ice is a fixed energy debt
Freezing one kilogram of water that arrives at 0 degrees Celsius removes about 334 kJ of latent heat. If the inlet water is at 20 degrees Celsius, another 84 kJ must be removed first, so roughly 420 kJ per kilogram is the refrigeration load before any losses. Convert to kilowatt hours by dividing by 3600 seconds per hour: 420 kJ is about 0.117 kWh of cooling per kilogram of ice. That figure is not a machine's consumption — it is the unavoidable thermodynamic floor. A real machine adds compressor inefficiency, fan and pump power, harvest energy and cabinet losses, which is why the electrical input per kilogram is always higher.
The formulas
| Quantity | Formula | Note |
|---|
| Upper-bound daily electricity | Rated power (kW) x 24 h | Assumes no idle time; a ceiling, not a forecast |
| Electricity per kilogram | Daily kWh / daily kg | Use it to compare listings on a like-for-like basis |
| Real daily electricity | kWh meter reading over 24 h | The only figure worth budgeting from |
| Water frozen into ice | Daily kg x 1.05 / 1000 | 1.05 allows for flush water; measure if precise |
| Condenser water (water-cooled) | Heat to reject (kW) / (4.186 x temperature rise K) | From the model's flow figure, or estimated |
| Monthly cost | kWh x tariff + m³ x water tariff | Use your own invoices, not averages |
Worked example using published wattages
Take three models from our range and apply the same arithmetic. The 200–500 kg/24h series is listed at 1860 W on 220–240 V. The ETD-1500P, at 750 kg/24h, is listed at 2800 W on 220 V single phase. The one-tonne series, at 1000 kg/24h, is listed at 3680 W on 220 V or 380 V three phase.
| Model | Rated power | 24 h upper bound | Per kg at rated output |
|---|
| 200–500 kg/24h series | 1860 W | 44.6 kWh | 0.089 kWh/kg at 500 kg |
| ETD-1500P, 750 kg/24h | 2800 W | 67.2 kWh | 0.090 kWh/kg at 750 kg |
| One-tonne series, 1000 kg/24h | 3680 W | 88.3 kWh | 0.088 kWh/kg at 1000 kg |
Two conclusions follow. First, the published wattage of these three models scales almost linearly with tonnage, which is what a well-matched range should look like; if one listing breaks the pattern badly, ask why. Second, the per-kilogram figures cluster just below the 0.117 kWh/kg physical floor for the cooling load — as they must, because the machine cannot beat thermodynamics. If any listing claims a per-kilogram number far below that floor, it is either a different tonnage or a mistake.
Then apply your tariff. At 0.15 USD per kWh, the 500 kg model's upper bound is 6.69 USD per day if it never idles, and proportionally less in practice because a machine with a full bin stops.
Water, in two parts
The first part is the water that becomes ice: for 500 kg of output, about 0.53 m³ per day. The second part exists only on water-cooled machines. With a permitted 10 K rise, each kilowatt of rejected heat needs about 0.086 m³/h; a machine rejecting roughly 1.4 times its electrical input therefore uses about 0.12 m³/h per kW of input while running. At a 0.5 USD per m³ water tariff, that is a real annual line item and belongs in the comparison — frequently it is the deciding factor between air and water cooling.
Verifying the estimate in the field
- Fit a kWh meter on the machine for one week. It captures duty cycle, night operation and the effect of a full bin.
- Weigh the ice produced in 24 hours from an empty bin, on a platform scale.
- Divide measured kWh by measured kilograms. That number is your site's real specific consumption, and it is the only one to compare year over year.
- For water-cooled units, fit a water meter on the condenser line for one day.
- Re-measure after any condenser cleaning. The difference tells you what maintenance is actually worth at your site.
What pushes the number up
- A hot room: the condenser works against a higher temperature, so the compressor runs longer for the same ice.
- Warm inlet water: each degree of inlet temperature is energy you pay for before freezing starts.
- Excessive ice thickness: thicker cubes take longer per cycle and use more energy per kilogram, not less.
- A dirty condenser: the coil cannot reject heat, so head pressure and current rise together.
- Running a large machine for a small daily need: idle and part-load operation is the least efficient regime.
FAQ
Is the rated wattage the running consumption? No. It is the input when the compressor and fans are running. Average consumption is lower if the machine reaches its bin setpoint and stops.
Do I need a three-phase supply to run a one-tonne machine? Both 220 V and 380 V configurations exist in our range; the three-phase version spreads current across phases and is generally kinder to the supply.
How accurate is the 1.05 flush factor? It is an allowance, not a measured value. Meter the supply if water cost matters to your business case.
Should I budget for a water treatment cost? Yes, where hardness is high. Filtration and descaling protect the kWh figure you just calculated.
Send us your daily requirement and your electricity and water tariffs and we will build this calculation for the exact model, using published wattage and your own rates. See the 100–500 kg/24h series, the 500–1000 kg/24h series, or the 750 kg/24h ETD-1500P, or request a running-cost sheet.
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