The Operation and Maintenance (O&M) cost of a component is the cost associated with operating and maintaining that component. The total O&M cost of the system is the sum of the O&M costs of each system component.
For most components, you enter the O&M cost as an annual amount. For a generator, you enter the O&M cost as an hourly value, and HOMER multiplies that by the operating hours per year to calculate the annual O&M cost.
The grid O&M cost is the annual cost of buying power from the grid minus any revenue earned from selling power to the grid.
HOMER classifies miscellaneous annual costs, such as the system fixed O&M cost, and penalties, such as emissions penalties and the capacity shortage penalty, as other O&M cost.
HOMER displays the O&M costs on the Cost Summary and Cash Flow tabs of the Simulation Results window.