asked the Secretary of State for Energy what is the estimated cost of building a heat grid of insulated hot water pipes for London.

The Government have no estimates of the cost of building a heat grid of insulated hot water pipes for London as a whole.However, following publication of the Marshall report on "Combined Heat and Electrical Power Generation in the United Kingdom", the Government commissioned W.S. Atkins and Partners Ltd. to carry out a study on the feasibility of combined heat and power district heating in nine cities.The report of this study, published as Energy Paper No. 53 in 1984, estimates that the cost of laying heat mains in the boroughs of Tower Hamlets and Southwark alone could be of the order of £174,574,000 at 1982 prices.