Operating reserve shortage VS Unmet load
A suitable loss of load cost allows comparing the grid-only supply (subject to interruption) with grid + backup generation.
The cost of interrupting the energy supply can be determined as the financial impact of disconnecting a load. Homer has one parameter related to this cost which is "capacity shortage penalty". However, it takes into account not only the unmet load but also the violation of operating reserve, which may have a lower value than the cost of the unmet load.
Is it possible to model a different penalty for operating reserve shortage and the unmet load?
Required Operating Capacity at any timestep is a sum of the actual load and the operating reserve.
So any non-zero value in the Maximum annual capacity shortage(%) input would also allow for unmet load.
So you can use this to have a penalty only for the unmet load, by making all the Operating Reserves zero and the Maximum annual capacity shortage non-zero.
The penalty you assign to capacity shortage, will be only for unmet load now.
Hope this helps!