def capacity_cost_rule(mod, g, p):
    """
    The capacity cost of projects of the *gen_spec* capacity type is a
    pre-specified number equal to the capacity times the per-mw fixed cost
    for each of the project's operational periods.
    """
    return mod.gen_spec_capacity_mw[g, p] * mod.gen_spec_fixed_cost_per_mw_yr[g, p]