When optimizing a generator in a generation design using HOMER, you will be required to fill out the Operations and Maintenance (O&M) cost. Since HOMER optimizes the generation component sizes based on the unit costs associated with each component, the O&M cost is the operation and maintenance cost you expect for each kilowatt (kW) of capacity, and for each hour of runtime. Thus the O&M input can be expressed as:

O&M ($/kW/hr) = (Yearly total O&M [$]) / (Generator size [kW]) / (Runtime [hr/yr])

A typical O&M cost to be entered into HOMER is between $0.01 - $0.03.