a heat pump will cost the same as putting a gas boiler in. but critics say its not ambitious enough. on a smaller scale, district heating will be another source of heating for homes. big underground hot water pipes supply heat to housing developments, there s a big new project planned in london, using heat produced from burning waste; heat can also come from large heat pumps based in rivers or even in the sea and then there s hydrogen ? an alternative that big energy companies are putting a lot of money into. they say their existing gas pipes can be used to supply hydrogen around the country. but the independent climate change committee, which advises the government, reckons hydrogen may end up heating only about 11% of uk homes. and the government has now delayed a decision on the potential use of hydrogen for heating buildings until as late as 2026. there are two methods of producing hydrogen. blue hydrogen creates greenhouse gas emissions during its production,