The question is whether the commission’s company-wide rate increase allowance for Ohio Power is unreasonable or unlawful as applied to the class of inter-ruptible power customers.

Appellants, as users of interruptible power, do not attack the propriety of the overall rate increase. They contend, however, that the increase, as applied to their classification, is improper without evidence relative to the cost to Ohio Power of furnishing such service. Although appellants imply that such cost is minimal, inasmuch as Ohio Power must maintain a power reserve in order to meet the fluctuating demand of its primary users regardless of whether it has interruptible power customers, they presented no cost study data respecting the interruptible power classification.

It should be noted that the increased rate approved for interruptible power service remains considerably lower than the rates for other customers and that the percentage of rate increase, as applied to interruptible power customers, is less than the percentage of rate increase approved for substantially all other classifications.

We find no statutory requirement in R. C. Chapters 4905 or 4909 as to the necessity of the commission making cost of service determinations relative to specific rate classifications. Nor do we find that the failure to make such specific determinations was unreasonable where the service afforded is from an overall reserve resulting from system-wide operation of Ohio Power,

*42We hold that the order of the commission is neither unreasonable nor unlawful, and it is, hereby, affirmed.

Order affirmed.