When a piece of equipment is not included in a scenario, all of the characteristics of that equipment type should also be null. This won't affect functionality as those values are not used anywhere in the calcs anyway, but it could easily be confusing for the user. See example screenshot below. I've selected to show 'Differences' and it shows there are entries for characteristics specific to AWHPs even when there is no AWHP defined for a scenario. Also, because all the characteristics of the WWHP are the same across scenarios, those don't show up at all when differences is selected, even though only one scenario actually has a WWHP defined.
When a piece of equipment is not included in a scenario, all of the characteristics of that equipment type should also be null. This won't affect functionality as those values are not used anywhere in the calcs anyway, but it could easily be confusing for the user. See example screenshot below. I've selected to show 'Differences' and it shows there are entries for characteristics specific to AWHPs even when there is no AWHP defined for a scenario. Also, because all the characteristics of the WWHP are the same across scenarios, those don't show up at all when differences is selected, even though only one scenario actually has a WWHP defined.