Stop press!
Recent reports prompted by press releases by the disposable nappy manufacturers seemed to suggest there was little difference in the environmental impact of washable compared to disposable nappies. However, the Environment Agency report was looking largely at energy use, and not at waste issues. It has always been the waste and resources issues that have been the major concern to the environment with disposable nappies. The report says there is little or no difference in energy use – so you can save waste and not use more energy.
In addition to this the report's findings were based on old-fashioned terry use where boiling nappies was common. With modern nappies this is not recommended practice so a reduction of about 24% energy use can easily be achieved by washing full loads at 60 oC in a modern energy-efficient washing machine.