From 1925 it cooperated with three other London companies, with the intention of centralising electricity generation in the new, high thermal efficiency, power station at Barking.

In addition to the power stations, work included the laying of cables in St Luke, Clerkenwell, Wandsworth, Putney, Streatham, Clapham, Holborn and Camberwell.

[7] By 1923 the plant comprised:[1] These machines had a total generating capacity of 27,500 kW of alternating current.

The following table summarises the growth of the company in terms of capacity of the plant, the electricity load, the amount of current sold, and the number of customers.

Capital expenditure was needed for the purchase of land, buildings, machinery, mains, transformers, meters, electrical instruments, legal costs, fixtures and furniture at the stations.

[1] The capital expenditure in 1896 and 1897, associated with the commissioning of the power stations at City Road and Wandsworth, amounted to:[1] Profits were made through the sale of electricity which provided an income for the Company and its shareholders.

By 1913 the County of London Company was supplying the Metropolitan Boroughs of Bermondsey, Camberwell, Finsbury, Holborn, Lambeth, Southwark and Wandsworth; the Urban Districts of Merton and Morden, Romford, and Tilbury; and the Rural Districts of Croydon, Orsett and Tilbury.

By 1937 the Company was supplying electricity additionally to: the Metropolitan Boroughs of Barking, Beddington and Wallington, Dagenham, Mitcham, Reigate, Sutton and Cheam and Wimbledon; the Urban Districts of Banstead, Billericay, Brentwood, Carshalton, Caterham and Warlingham, Hornchurch, Thurrock, Wanstead and Woodford; and the Rural Districts of Epping, and Godstone.

[15] It was able to consolidate development over a large area of south east England through its Kent Power Company subsidiary.

[15] In 1920, the County of London Electric Supply Company applied for permission to build a power station at Creekmouth in Barking capable of expansion to 600 MW.

[16] The companies remained district electricity supply undertakings; although they were physically joined with interconnecting cables.

Dividends to shareholders were limited to 7 percent per year and the funds that could be carried forward in the accounts were restricted.

[18] The CEB identified high efficiency ‘selected’ power stations that would supply electricity most effectively.