In the model that a firm produces one commodity, say electricity by the use of two factors, say capital and a resource under the rate of return regulation on capital, we analyse the firm's optimal behaviour, when one of the factor prices is uucertain. Our conclusion is that if the resource price is uncertain, the firm's risk attitude and the degree in risk influence the firm's resource allocation, but if the capital price is uncertain, this uncertainty never affects the optimal level of factor employment.