Paper does not single out one of Regressions A/B/C; the flexible PA models 'give similar long run elasticities' and the 2SLS price elasticity 'generally range from -0.3 to -0.6 and are almost always significant' (p.261, Table 3). Regression A (-0.40, t=3.09) best represents this significant headline range || 'The 2SLS electricity price elasticity estimates generally range from -0.3 to -0.6 and are almost always significant' (p.261)
Westley, G. D. (1989a): “Nontraditional Partial Adjustment Models and Their Use in Estimating the Residential Demand for Electricity in Costa Rica.” Land Economics 65(3), 254-271