Authors explicitly accept solution 2 (Table 2), NOT solution 1 from which the coded cell is drawn: solution-2 own-price elasticities are PM1=-0.0443, PM2=-0.1531, PM3=-0.1947 || 'Unlike the results derived from the first model, all the GEC parameter estimates from the second solution have theoretically correct signs and are highly significant statistically. Therefore, we accept this specification as the one which most appropriately represents the residential demand for electricity.' (p.336). The single coded cell is Table 1 (solution 1) GEC PM1, which is not the authors' preferred specification; preferred left at 0 on the existing cell.
Parhizgari, A. M., and P. S. Davis (1978): "The Residential Demand for Electricity: A Variant Parameters Approach." Applied Economics 10(4), 331-40