Oni Cooling Calculator

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Heat to be moved & deleted

Heat deletion options


Cooling in Oni is a two step process:

  1. Conduct the heat away from what you want to cool to somewhere it can be deleted.
  2. Delete the heat.

This tool lets you calculate how much heat energy you need to move and delete, then provides options for how you can delete that heat, along with the running costs to order to operate that heat deletion method. As seen on Youtube Brothgar.

Heat deletion options

Four common heat deletion options provided by the tool:

  • Wheezwort: It is assumed that the wheezwort are saturated in hydrogen and therefore providing their maximum heat deletion power of 12,000 DTU/s.
  • Thermo-nullifier: It is assumed the Thermo-nullifier is saturated in hydrogen and providing its full heat deletion power of 80,000 DTU/s.
  • Space boiling: By boiling a liquid into space (void), the hot gas is then lost and all of its thermal energy is also deleted. By default the boiler assumes that polluted water is the boiling liquid and that it starts at 40C before heat is conducted into it by a thermo aqua-tuner or thermo regulator. This can be adjusted in advanced settings. The polluted water will continue soaking heat past boiling point (119.35+2C) until it reaches the defined release temp, by default this is 1,000C but can be changed in the advanced settings. Once at this temp a door would open releasing the superheated gas to space for deletion. This build assumed access to Thermium to handle the temperatures, you can have a less efficient build by using lower class metals and lowering the gas release temperature.
  • Steam Turbine The Steam Turbine converts heat energy directly into electricity at a rate of 1032.46DTU/s -> 1Watt. At peak operation the generator will covert heat into electricity at an average rate of 877,590DTU/s -> 850W. Excess energy put into the steam will be deleted without additional electricity production. The machine takes steam of at least 125C and outputs water at a fixed 95C. Each of the intake pipes can intake 400g/s of steam, meaning a maximum of 2kg/s if all 5 intakes are saturated. By default the tool assumes you are dumping heat into the steam until it hits 200C (at 5 open inputs this would operate the machine at the maximum 850W), at which point the turbine turns on. At higher temperatures you require less steam per second to maintain the energy output. Note, the turbine re-outputs heat at a rate of 4kDTU + 10% of the heat it deletes. E.g. at just enough energy for maximum wattage the machine will be heating itself at a rate of 91.8kDTU. This heat should be looped back into the steam chamber for deletion. To prevent infinite recursion, several weezewort in the turbine room would help.
  • Ice Machine The Ice machine removes 20,000 DTU/s from the water inserted into it but outputs only 16,000 DTU/s while in operation, deleting 4,000 DTU/s in the process of cooling down the water to blocks of ice at -20C. Cooling the water consumes 60W. Because the machine provides a flat cooling factor, it takes longer to cool hotter water down to the same -20C target.
  • Other options There are several other options to delete heat that are more difficult to practice on a scale like the ones above but one should nonetheless consider when designing their base to achieve heat deleting as a by-product of processes you were likely to do anyway. This includes: (a) dumping heat into water that you were going to electrolyze anyway (b) dumping heat into a fuel you were going to burn anyway (e.g. hydrogen in a generator, petroleum in your rocket).

No assumptions have been made for additional heat introduced into the system via heat transfer methods. E.g. a liquid pump will add 2k DTU/s, your power sources may generate heat, etc.

Running cost assumptions

Running cost assumptions are a best case scenario and should be considered a minimum for all cases:

  • Wheezworts. If fertilized, each Wheez will consume 5kg of Phosphorite per cycle. If not fertilized, there are no costs but the Wheeze operate at 25% of the maximum cooling output.
  • Thermo-nullifier. Running cost of 10g/s per thermo-nullifier and the associated energy to drive the hydrogen to the nullifier through a pipe.
  • Boiler. Similar to the sieve arrangement, it is assumed that heat is being moved into the boiling medium through a super coolant closed loop. Pumping the liquid into the boil chamber would also consume some small amount of electricity. Importantly, once boiled and released the element itself is also lost and shown as a further running cost.
  • Steam turbine. Similar to other methods, it is assumed that heat is being moved into the steam through a super coolant closed loop. The turbine itself however will generate an offsetting amount of electricity. It is assumed the water output by the turbine is looped back through to the steam chamber and requires no additional pumping.
  • Ice machine. The ice machine is a complex method to calculate running costs for. It's first cost is simple electricity of 60W per machine at 100% uptime. However, the ice machine is the only method in this tool that can not be automated and requires dupe time. How much dupe time is a factor of how you build your base and the other tasks dupes have to complete and where they are when the ice machine falls on their priority list. The amount of dupe time lost can be minimized by filling the ice machine with the hottest water possible, reducing the number of time the machine must be loaded.


It would be advisable to round up the number of Wheezworts required by at least one in order to (i) account of heat entering the system though non-perfect insulators (ii) to help the system reach steady state faster.

Wheezeworts and Thermo-nullifiers can be automated by building them on doors.

Wheezeworts would generally be considered the optimal heat deleter for two reasons (i) they can have zero running costs (ii) they are themselves infinitely obtainable. Until the player has access to them on an icy planet however, they are limited and should be used efficiently.

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