Abstract and Section III flag the marginal-price coefficient as the theoretically 'right' own-price effect (negative, expected inverse relationship); average price is interpreted as an income/intra-marginal effect. || 'the coefficient on marginal price is ‘right’; that is, the expected inverse relationship between the quantity of electricity demanded and the marginal price it obtains' (p.377); '(2) the elasticity of marginal price is −0.11' (p.383)
Roth, T. P. (1981): “Average and Marginal Price Changes and the Demand for Electricity: An Econometric Study.” Applied Economics 13(3), 377-388