This guide was inspired by Project Incursus and Frazzz (for two very, very different reasons) and explores the ramifications of upgrading your mines and turbines.

TL;DR Skip to the Break-Even Point table.

First let's cover the costs of building vs upgrading in terms of both time and resources, and the income produced by each device assuming 100% Turbine efficiency.

Building Costs

Upgrading Costs

Income

(H) signifies Hurricane Commander.
(O) signifies Overdrive Commander
(P) signifies Pinchfist Commander.
(U) signifies upgraded device.

Quite simply, the Break-Even Point is the point in time when your investment finishes paying for itself. Investment cost includes both the up front cost as well as any lost income due to the device being offline.

For example, a standard mine costs 75 metal to upgrade and is offline for 22 seconds while upgrading. During those 22 seconds, had it been online it would have generated an additional 4 metal per second, or 88 metal. That gives a total metal cost of 75 + 88, or 163 metal. An upgraded mine produces 6, rather than 4 metal per second, meaning that once it has completed it will be recouping 2 metal per second on that 163. The up front cost in terms of time is 22 seconds, and then another 82 seconds is necessary to reach the break-even point at 104 seconds.

In comparison, building a new mine would have a much higher up front cost of 300 metal, but no income would be lost as no existing mine is taken offline. After 30 seconds, it would be recouping the investment at a rate of 4 per second, reaching the break-even point after 75 seconds of operation, or 105 seconds total. To look at it another way, an upgraded mine takes 104 seconds to pay back the 163 total metal investment, while purchasing a new mine takes only 1 second longer to repay the 300 spent. After the break-even point is reached, the new mine would be outpacing the upgraded mine at a rate of 2 per second.

For upgrading Turbines, the total energy cost is an initial 1000, plus 15 seconds (Note: prior to update 1.14 July 7th, upgrade time was 30 seconds) offline at 45 energy per second, for a total of 1675 energy. Once upgraded, energy production increases to 67.5, so it would be recovering that 1675 at a rate of 22.5 per second, reaching its break-even point at a total of 90 seconds. In comparison, a new turbine costs 800 energy and completes within 20 seconds, generating an additional 45 energy per second. 18 seconds of operation is sufficient to recoup that 800, so the break-even point is reached in a mere 38 seconds. After which it would be outpacing the upgraded turbine at a rate of 22.5 per second.

Because different commanders affect the building times and income generated by devices, the break-even point can change as a result. Here's a quick summary:

Break-Even Point

While the numbers seemingly speak for themselves, they aren't the whole story. Fort design, defensibility, wind ceilings, turbine efficiency, wind obstructions, starting resources, the number of placements available, weight and joint stress and more all factor in. Sometimes it's better to focus on one efficient turbine you can keep alive rather than building several minimum efficiency turbines you can't possibly defend. Some maps are severely limited in the number of mine locations, or your strategy requires them for swarm missiles or warheads. Whatever you choose, I hope this guide helps you make the best decisions.

Finally, for anyone interested in a comparison between the various commanders and upgrading vs building new, I've included some tables that chart out the income from a single mine or turbine out to the 150th second. I was a bit constrained by the Steam limits on character counts and width, so abbreviations were used when necessary. N signifies building New, while U signifies upgrading. Break-even points indicated thusly.

The following information is no longer current as of balance update 1.14 released July 7th. However, some may still find it useful for providing context when reviewing older recorded matches.

The break-even point is the moment at which the total cost of building or upgrading a device is returned by that device. Total cost includes both the up front cost as well as any lost income due to the device being offline. For example, a standard mine costs 75 metal to upgrade and is offline for 22 seconds while upgrading. During those 22 seconds, had it been online it would have generated an additional 4 metal per second, or 88 metal. That gives a total metal cost of 75 + 88, or 163 metal. An upgraded mine produces 6, rather than 4 metal per second, meaning that once it has completed it will be recouping 2 metal per second on that 163. The up front cost in terms of time is 22 seconds, and then another 82 seconds is necessary to reach the break-even point at 104 seconds.

In comparison, building a new mine would have a much higher up front cost of 300 metal, but no income would be lost as no existing mine is taken offline. After 30 seconds, it would be recouping the investment at a rate of 4 per second, reaching the break-even point after 75 seconds of operation, or 105 seconds total. To look at it another way, an upgraded mine takes 104 seconds to pay back the 163 total metal investment, while purchasing a new mine takes only 1 second longer to repay the 300 spent. After the break-even point is reached, the new mine would be outpacing the upgraded mine at a rate of 2 per second.

For upgrading Turbines, the total energy cost is an initial 1000, plus 30 seconds offline at 45 energy per second, for a total of 2350 energy. Once upgraded, energy production increases to 67.5, so it would be recovering that 2350 at a rate of 22.5 per second, reaching its break-even point at a total of 135 seconds. In comparison, a new turbine costs 800 energy and completes within 20 seconds, generating an additional 45 energy per second. 18 seconds of operation is sufficient to recoup that 800, so the break-even point is reached in a mere 38 seconds. After which it would be outpacing the upgraded turbine at a rate of 22.5 per second.

Because different commanders affect the building times and income generated by devices, the break-even point can change as a result. Here's a quick summary:


Note: Prior to ToG 1.10 (released April 20th, 2018) upgraded mines only produced 5 rather than 6 metal, for a break-even point of 185 seconds. Turbine upgrade metal cost was also reduced to 100 metal from 200.