To popularise the use electricity, the CESC used to bring out advertisements in the newspapers. These advertisements had captions like: Electricity will introduce new style in your life; Electricity is so cheap; Electricity is an efficient servant at your fingertips. Slogans like these may appear funny to today's newspaper readers but these very word motivated many a Calcuttan to switch over to electric bulbs from trusted old oil lamps.

Very soon the increased use of and demand for electricity forced the CESC to commission more power plants. One power plant with a capacity of 0.75 MW was installed in the Alipur area in March 1902. Another plant with an installed capacity of 0.165 MW came up in Howrah in May 1906. In September 1906, till then the biggest power plant (installed capacity 1.2 MW) was commissioned in the Ultadnaga area of Calcutta. In September 1910, the power sector of the country entered a new era with the introduction of the Ac system. By December 1909, the CESC felt the need to install a central thermal power station in Calcutta and three years later a plant with an installed capacity of 15 MW was commissioned in the Cossipore area of Calcutta. Oerlicon Company manufactured the steam turbine of the newly built thermal power station. The boiler came from Sterling AMD and Babcock Small and Wilcox Co. The power generated at the busbar of Cossipore thermal kpower station was available in 6KV SE but the distribution network was in DC system. To facilitate commercial operation, three motor converters were installed at Jackson lane, Welesely Street and Princess Street. These motor converters were manufactured by Broosh Peebles Co. and were named as sub-stations. Later, the generating stations of Ultadanga, Howrah and Alipur were all converted into sub-stations. In the second decade of this century a one-megawatt thermal power station was installed near Barrackpore, a suburb of Calcutta.

Till 1907, the CESC operated from the office of Killburn Co. On 1st January 1908, CESC shifted to another rented building at 8 Dalhousie Square, and then again to 6 old post office street. But by 1920, the CESC authorities realised that it was not possible to operate from rented accommodations. A plot of land was bought in the heart of the city in 1926 and the construction work started immediately. The building was named Victoria House, after the London Office of CESC. By 1926, the central commercial area of Calcutta - Chowringhee - was electrified. In December 1902, the horse-drawn tramcars of Calcutta was converted to electric tramcars. The southern generating stations (2X75 MW) of the CESC started operation in 1926. This power station, located in the Gardenreach area of the city, was further expanded in 1928, 1931, 1934, 1937 and 1946. In the 1990s, the southern generating station was demolished, giving way to a new station of 67.5X2 MW capacity.

To cater to the increasing needs of a growing city, the CESC commissioned the Mulejore power plant in the Shyamnagar area, another suburb of Calcutta, during the Second World War. Three 30 MW units were commissioned in 1939, 1940 and 1950 and two similar units were installed in 1951-53. As most of the industrial units in and around Calcutta were located on the other side of River Hooghly - in Howrah - the CESC started constructing a new transmission network for the area in 1910. Two cables weighing 12 tonne each were laid in the riverbed of the Hooghly. It took 199 years to executing the project, in which a 690-yard long tunnel of 6 feet diameter was constructed 90 feet under the riverbed. British Engineers carried out the designing and supervision of the construction work and Indians did the rest of the works. The new transmission system was completed in September 1931.

During the Second World War, demand for electricity in and around Calcutta increased manifold. This prompted the government took initiative in the power sector. In 1946, the Electricity Development Directorate (EDD) was formed under the Government of Bengal. Before the launching of the EDD, there were 25 private power companies in the state of present West Bengal. They were allowed to supply power to 37 cities and towns of the State of West Bengal.

In fact, Bengal (now West Bengal) is the first province (now a State) of the Indian Sub-continent which pioneered in installation of both hydel and thermal power stations to generate electricity, the wizard of modern times.