As with all other aspects of society, the war had a major effect on the gas industry - the increase in demand for chemical products for munitions manufacture; the shortage of male workers and the recruitment of females; large increases in the costs of materials and labour combined with controls over the charges for gas. With restrictions in the availability of engineering materials, the construction and maintenance of gasworks plant was curtailed.
The Gas Regulation Act 1920 changed the basis of charging for gas and introduced a national basis for the testing and reporting of gas quality. From the start of gas regulation in the mid 19th century the quality of gas had been judged by its illuminating power. The act changed this to the heating power (calorific value) of the gas.
The post-war depression affected the gas industry as much as any other; some smaller companies went bankrupt and amalgamations continued. The 1930's saw the rise of the holding company. Holding companies bought up control of gas undertakings, allowed them to continue to trade as the original company and provided central control and assistance in financial, management and technical areas. By 1949 there were some 14 holding companies controlling about 260 undertakings.
In 1939 war again brought the problems of 1914 but with the added damage to gasworks and to apparatus in the street caused by air raids. It was obvious that when the war was over major work would be required to reconstruct the industry. In 1944, the Ministry of Fuel and Power set up a Committee of Enquiry under the Chairmanship of Geoffrey Heyworth 'To review the structure and organisation of the Gas Industry, to advise what changes have now become necessary in order to develop and cheapen gas supplies to all types of consumers and to make recommendations'. The Heyworth Report was published in December 1945. While it did not itself recommend nationalisation, the report formed the basis of the Gas Act 1948 which nationalised the gas industry in England, Scotland and Wales.