Equation (21) (quadratic-discomfort / linear utilization form, elasticity 0.0447) is the author's preferred utilization specification || 'Since the fit of equation (21) is marginally better (with more precise estimates of the coefficients) than the fit using the exponential specification embodied in equation (13), we shall only present results using the quadratic specification of discomfort' (p.47) and abstract 'The utilization equation indicates a relatively low price elasticity' (p.33)
Hausman, J. (1979): “Individual Discount Rates and the Purchase and Utilization of Energy-Using Durables.” The Bell Journal of Economics 10(1), 197-212