distance between lamps in the same group is 15 cm, and the distance between any two groups is 21 cm (Fig. 3). The solar simulator can generate suitable irradiance intensity values, as required at two different distances between lamps and test area. Radiation output value for both group B and C is 1066 ±15 W/m2 at 26 cm distance from lamps to test area with non-uniformity 8.5% with test area sufficient to test only one electricity meter. Radiation output value for the three groups A, B and C is 1026 ±15 W/m2 at 32 cm distance with non-uniformity 9.6% and surface test area sufficient to test two electricity meter at the same time. Fig. 4 shows the radiation distribution inside the solar simulator at two different distances. Uncertainty Sources Table 1 - Uncertainty budget of accuracy measurements at 220 V, 10 A Standard Repeatability of readings Calibration certificate Resolution of the instruments Drift of NIS Standard since last calibration Accuracy of reference Scan head Effect of short-term stability of the applied power Combined standard uncertainty Effective degrees of freedom Expanded uncertainty at confidence level 95% (k=2) Table 2 - Accuracy test results for the first electricity meter Applied Current (A) 1 5 10 20 50 80 100 1 5 10 20 50 80 100 1 5 10 20 50 80 100 54 0.5 (Inductive) 0.8 (Capacitive) 1 (Resistive) Powerfactor Error % before test