I've been playing this game for about 6 months. Almost all of the upgrades have had some reasonable basis for taking them as I've gone along. But I can't figure out why I'd want to do the Thorium Reactors upgrade since I don't have any reliable source of Thorium. If I put all of my factory workers on Thorium I could produce 9.64 Thorium/second. That would get burned up pretty quick by 53 reactors at .25/second. There are no buildings or planets for producing Thorium. Plus it is taking a week's build-up of Thorium at this point for me to get the next level of Heatsink so it would take months if the Thorium was also getting eaten by the Reactors. So why should anybody upgrade to Thorium Reactors?

3 Answers 3


The upgrade is togglable, meaning you can turn it off and on with no penalty. There are a number of reasons you should want to turn it on for some time:

  • to supply more electricity to temporarily turn on some energy-expensive stuff, like heatsinks, or accelerators (more pocket rifts).
  • to combat the electricity cuts by some calendar cycles (Dune ⍫ and Terminus ⍝) - this is only if you have the Numerology metaphysics upgrade.
  • once you get past a certain point, the bonus you will get from it will be large enough to supply accelerators to get enough uranium, though I don't expect this to be possible before quite a few resets for paragon bonuses and metaphysics.
  • in case your net electricity production is just below zero, you can toggle it on every once in a while to use the excess thorium and get a minor production bonus.

Thorium can be crafted from Uranium, which can be generated from Accelerators or planet crackers.

If this upgrade doesn't do anything for you now, that's fine. Don't use it now. It'll be useful in the future.

Not all upgrades are immediately useful, and late game has many cases of this.


Here are some hard numbers from my game to give you an idea when thorium mode becomes practical.

Overview: 1801 total years played (about a year in real time, with breaks). Just before 6th reset. Had all techs and upgrades obtainable without AM or TC. All rates below are without Tempus Fugit.

At this point, I was producing 407 U/s. With crafting at 1694%, I could craft 29.2 Th/s. In thorium mode, my 85 reactors were consuming only 15.9 Th/s.

There are two points that would affect other players’ experience, relative to mine. First, I didn’t need Th for anything else; I’d already bought all the upgrades and flown to all the planets I could, and I wasn’t building any heatsinks or tectonics.

Second, I always play interactively, so I can craft Th manually whenever I need to. My 94 engineers could not at first keep up with the 85 reactors. After I promoted everyone to the max (Rank 4), they could keep up, barely. With no engineers, each 1K Th lasts about a minute. With all engineers, the drain would be slower, but I couldn’t easily measure it.


Uranium from 73 accelerators, 160 quarries, 24 planet crackers. +290% from 480 paragon and 230 burned, +1280% from 64 magnetos with 60 steamworks, +855% from 435M praised faith, +40% space conversion (94 factories, 32 space elevators, 4 orbital arrays).

Craft ratio from 187 workshops, 94 factories, +8 from artisan leader with 230 burned.

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