Model I is the constant-elasticity (double-log) specification the author uses as the benchmark for external comparison || 'the constant elasticity model employed here yields an estimate for Virginia Electric Power Co of -0.21 ... for Pacific Gas and Electric of -0.43' (p.27); Model I column 'follows directly from the price elasticity estimates in regression Equation (12)' (Table 4/8 notes). Marked the 12 Model I cells preferred.
Betancourt, R. R. (1981): “An Econometric Analysis of Peak Electricity Demand in the Short-Run.” Energy Economics 3(1), 14-29