Costing

A shorter queue is nice. A client funds a change when you can show what it costs and what it saves. Costing puts money on your simulation so you can make that case.

What Quodsi costs

You set rates on activities and resources. The cost of a run then comes from what actually happened in it, including idle time. You'd struggle to work that out in a spreadsheet, because it depends on queues and variability.

Each activity and resource has a Financial tab, in every complexity view, though resources themselves appear from the Intermediate view. Turn on financial tracking first. Nothing is costed until you do.

Activity costs

Turn on Enable financial tracking on the activity.

Setting	What it charges	Example
Fixed Cost	Once per run, per unit of capacity. Doubling capacity doubles it. On a work schedule, the capacity is the schedule's busiest count during the run: a schedule of 2 that rises to 4 is charged for 4, whatever the activity's own Capacity says.	A workstation lease
Cost Per Entity Processed	Each time an entity starts at this activity, so an entity still here when the run ends is counted.	Materials for one test
Cost / Hour Active	Each hour, for each unit of capacity while a Delay is running on it.	Equipment running cost
Cost / Hour Idle	Each hour, for each unit of capacity on shift with no Delay running on it, including a unit held by an entity that is waiting and a unit under repair.	Keeping a line powered
Resource Cost Multiplier	Multiplies the Cost Per Seize and Cost Per Hour Utilized of every resource this activity takes up, for the whole time it's held, even if the entity lets it go at a later step. A resource's idle cost isn't multiplied. 1 means no change; 1.5 means half as much again.	Overtime or premium rates at one step

Resource costs

Turn on Enable Financial Tracking on the resource.

Setting	What it charges	Example
Cost Per Seize	Each time the resource is taken up.	A call-out fee
Cost Per Hour Utilized	Each hour the resource is working.	A nurse's loaded wage
Cost Per Hour Idle	Each hour, for each unit of the resource that is available but unused. Only on-shift idle time is charged.	The same wage, while waiting for patients

For staff who are paid whether they're busy or not, set the same rate for utilized and idle hours. Then spare capacity shows up as real money, which is often the point of the exercise.

Read the cost of a run

The Overview tab shows Total cost, with its change from the Baseline. If it reads No cost rates set, no costs are in the model yet. Costs show in dollars.

Figure	What it means
Total cost	What the whole process cost over the statistics window: total activity cost plus total resource cost.
Total activity cost	What the work steps cost: fixed, processing and operational costs across all activities.
Total resource cost	What the people and equipment cost: seize, utilization and idle costs across all resources.

To see where the money went:

On the Diagram tab, the Cost view puts cost on each shape.
On the Dashboard tab, add Resources: Cost to rank resources, Scenarios: Total Cost to rank scenarios, or Activities: Cost over time and Resources: Cost over time to see when the spend happened.
Add Activity × Entity: Cost to see what each kind of work costs at each step. Each entity type pays for the hours it was actually worked on, and its own per-entity charges. Idle hours are shared by how long each type held the step, so a type that waits or is blocked while holding a unit pays more of the idle cost, not more of the active cost. Fixed cost is shared by how many of each type the step served.

High idle cost next to low utilization is the classic sign of over-provisioning.

A resource still held when the run ends is charged for the time it was held. A unit working past its shift is charged at the utilized rate for that time, and it isn't idle. See Work schedule.

A hold is charged whole, when it ends. If it began during the warm-up, its whole length counts, including the part before the warm-up ended. A resource held from minute 1 to the end of a 10-minute run with a 4-minute warm-up is charged 9 minutes, though the statistics window is 6.

Costs accrue over the statistics window, which starts after the warm-up. A Fixed Cost is the exception: it's a one-time charge for the run, so it always counts in full.

Cost per entity

Quodsi reports two costs per finished entity, by entity type. On the Dashboard tab, add a Data table card, set Data to Entity and show All columns rather than Key. You'll find Direct Cost per Entity and Fully Loaded Cost per Entity there. Both also work as Tradeoff View axes under the entity group.

	Direct cost per entity	Fully loaded cost per entity
What it is	What one finished entity of this type cost in the work it actually used: per-entity charges, activity hours while it was being worked on, resource seizes and resource hours.	This type's share of everything the run cost, including idle resources and fixed costs, per finished entity.
What it leaves out	Idle and fixed costs.	Nothing. Per-type shares add up to Total cost.
Use it for	Showing that a process change really makes each unit cheaper. It moves when the process changes.	Pricing, and the full cost picture a finance lead will ask for.

The gap between them is worth showing a client. It's what spare capacity and overhead cost per unit. If a change shrinks the gap, the client is paying less for capacity they don't use.

"Finished" here means the entity left its flow, whether it was completed, consumed, split or disposed.

Build the business case

Get rates you can defend. Ask finance for loaded wages and running costs, and write down where each came from.
Set up the Baseline. Compare its Total cost with what the client actually spends. If they disagree badly, fix the rates or the model before going further.
Run the proposal. Use a scenario, or a study to size the change. Cost settings can be swept too.
Plot it. In Tradeoff View, put Total cost on one axis and the outcome on the other. Find where more spend stops paying off.
State the case per unit. Report Direct and Fully loaded cost per entity before and after. "Fully loaded cost per patient falls" is a line a client can act on.

Quodsi costs the running of the process. One-off project costs, such as construction or software, aren't in the run unless you model them as a fixed cost. Keep them in your wider business case.