Authors explicitly prefer the simultaneous-equation (3SLS) estimates over the flow-adjustment model, and all 9 coded obs are the 3SLS own-price elasticities || 'Simultaneous equation models seem to be more appropriate, since they provide negative price elasticity estimates for the residential, industrial and total electricity samples.' (p.97) and 'The residential price elasticity estimates range between -0.85 and -0.94, whereas the industrial estimates range between -0.34 and -0.55... Total electricity demand ... has price elasticity estimates between -0.13 and -0.15.' (p.97-98)
Kamerschen, D. and D. Porter (2004): “The Demand for Residential, Industrial and Total Electricity, 1973-1998." Energy Economics 26(1), 87-100