Paper's contribution is a single log-linear regression that includes BOTH average (intra-marginal) price and marginal price; both are the authors' headline own-price elasticities. || 'First examine the coefficients for average price and marginal price. Both have the correct sign and are of acceptable magnitude. The t-statistics are highly significant.' (p.701)
Garbacz, C. (1983b): “Electricity Demand and the Elasticity of Intra-Marginal Price.” Applied Economics 15(5), 699-701