The best way to use HOMER and Carbon?  Two scenarios suppose you are carbon capped would you just put in a fuel cap. If you are carbon taxed would you just add cost to fuel.

You can limit or penalize emissions if you click the Emissions button under the Project tab.

To cap carbon dioxide emissions, click the Carbon dioxide checkbox on the upper right side of the Emissions window and enter the maximum allowable emissions in kg/yr.  To apply a carbon tax enter the penalty in $/tonne in the Emissions Penalties section of the window.