Electrical power generation by Diesel engine + electrical Generator (DG) sets consumes precious fossil fuels. In the present work, performance of two different DG sets of 3 kW and 100 kW ratings are compared when they were additionally supplied with wood derived Producer Gas (PG) generated in a gasifier. The PG was cleaned and cooled before it was supplied to the DG sets. The salient feature of 3 kW system is that the PG does not come into direct contact with water during cleaning and cooling, whereas it does so in 100 kW system. In the experiments, both DG sets were operated in fully diesel and dual fuel (PG + diesel) modes. Diesel Consumption Rate, Diesel Replacement Percentage, Specific Diesel Consumption, Electrical Conversion Efficiency were calculated for the DG sets. Because of certain improved features and operating conditions, the 100 kW DG set could be operated more efficiently than the 3 kW DG set. Hence, electrical power generation by DG set using PG + diesel can be achieved more economically at higher power ratings.