you can have a look at smartprocurement website, as I am also trying to learn and understand the TCO concept and how we can implement for our commodities.

Here you will find a detailed description of TCO and also links to relevant material.

There are obvious differences in the sourcing of Capital commodities. I suggest an approach that looks at whole life cycle costing rather than TCO, the difference (in my opinion) being the consideration of the cost of a capital commodity from concept through to disposal. How would the benefit (in the sourcing of capital commodities) be quantified (NPV improvement, Cost avoidance / containment, financing cost reduction) ??? Are there any frameworks that could be used to specifically model life cycle costs of capital commodities?