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Mobile vs stationary plant ROI comparison
Asking the mobile vs stationary plant ROI comparison question correctly
When two quotations lie side by side, the purchase price is what the eye reaches first, and it is not where the decision is made. A mobile vs stationary plant ROI comparison only becomes answerable once every payment across the life of the asset is placed on a single time axis: machine cost, foundations and erection, annual operating cost, number of relocations and the number of years the plant will actually run. A comparison made without discounting those items to present value protects the first year's budget and wrecks the eighth year's cash flow. The same discipline applies across all investment and cost decisions.
The unit of comparison is total cost per tonne
The only common denominator between two different configurations is the tonne they produce. So the table takes the cost lines first, adds annual tonnage second, and reduces everything to a cost per tonne. The table below shows where the two options genuinely diverge.
| Cost line | Mobile setup | Stationary setup | What tips the decision |
|---|---|---|---|
| Machine investment | Usually lower | Usually higher | Compare at equal capacity, not at equal price |
| Foundations and steelwork | Minimal | Substantial and one-off | A poor soil survey can inflate this line |
| Erection and commissioning | Short, repeated at every move | Long, done once | The repeat count decides the total |
| Energy | Generator sets are common | Grid connection is common | With no grid, the stationary advantage evaporates |
| Haulage | The plant travels | The material travels | Check which side is building the road |
| Residual value | Broad second-hand demand | Site-bound and low | What comes back when the pit closes |
A simple present-value model
The model below contains no prices; every amount is indexed with the mobile machine investment set at 100 units. The assumptions are stated openly: eight-year life, a 12 per cent discount rate, annual operating cost of 22 units for mobile and 18 for stationary, 130 units of machine plus 25 units of foundation and erection on the stationary side, and 4 units for each mobile relocation.
| Scenario | Moves per year | Eight-year present value (units) | Outcome |
|---|---|---|---|
| Mobile, stays on one site | 0 | 209 | Mobile clearly ahead |
| Mobile, one move a year | 1 | 229 | Mobile still ahead |
| Mobile, two moves a year | 2 | 249 | Level with stationary |
| Mobile, three moves a year | 3 | 269 | Stationary moves ahead |
| Stationary plant | None | 244 | Reference value |
What the model delivers is not one number but the location of the crossover: under these assumptions the two options meet at roughly two relocations a year. Substituting your own figures moves the crossover, yet the structure of the question stays identical.
Four variables that flip the answer
No investment case matures without sensitivity work. Flexed one at a time, these four move the result the most.
- Reserve life: where the reserve lasts five years, the stationary foundation and erection cost spreads over five years rather than eight, and cost per tonne rises accordingly.
- Relocation frequency: the single genuine weakness of the mobile case, because each move costs both money and lost production.
- Energy source: a grid connection creates a clear operating advantage for the stationary plant; without one, both sides depend on gensets.
- Capacity utilization: low utilization hurts both, but the stationary plant bleeds faster because more of its cost is fixed.
Lost production is a cost line too
Relocation cost is not just lowboy and crane hire. Through dismantling, transport, erection and commissioning the line produces nothing, and those tonnes belong in the calculation. Because lost production days rarely appear in any budget, a plant that moves twice a year is routinely compared on terms unfair to the stationary option. The stationary side hides a line of its own: when the pit closes, concrete foundations and steel structures that cannot be lifted are worth close to nothing. Until both hidden lines are written down, the comparison stays incomplete and the lower up-front option usually wins undeservedly.
A short list as a decision rule
For an investor who knows the site and the reserve, the decision reduces to a handful of questions: how many years the reserve lasts, how often the plant will move, whether grid power exists, where the product is sold, and what remains once the pit closes. With those five answers written down, the technical criteria in the mobile tracked fixed plant selection comparison cover portability, foundation requirements and erection time in detail.
Frequently asked questions
How should the discount rate be chosen?
Use your own cost of finance. The higher the rate, the lighter future operating costs become, which works against the option carrying the larger up-front investment.
Should residual value be modelled?
Yes, but on both sides. Mobile units usually enjoy wider second-hand demand, while part of a stationary plant's residual value is buried in the site and cannot be recovered.
Does a hybrid arrangement make sense?
Frequently it is the best answer: a fixed line at the long-life main quarry, a mobile unit for short jobs. Model the two together against combined annual tonnage rather than separately.
Set the quotation aside and write five assumption lines first: reserve years, annual tonnage, moves per year, energy source, finance rate. Send that list over and we will build the model on your numbers and show where the crossover falls on your own site.
Definitions of technical terms: Glossary
