Adam Corner's Guardian article "When energy-saving does not mean saving energy" looks at rebound effects: "But a newly published paper in the journal Energy Policy shows that even straightforward carbon-saving activities such as home insulation are not always quite what they seem. The problem is that making one change around the house leaves the door open for other changes – which might include 'rebound effects' that undermine the carbon savings. If a driver who replaces their car with a fuel-efficient model takes advantage of the cheaper running costs and drives further and more often, then the amount of carbon saved is clearly reduced."
In the current economic climate that really should not be the case as 10-20% energy saving will only result in a cost "saving" that will offset rising energy prices, a trend that is likely to continue. The global economy is still growing relatively slowly but when this growth accelerates, demand for energy will increase putting further pressure on energy prices over the longer term.
Also, the way the domestic energy market operates in the UK, with suppliers buying gas and oil up to a year in advance will continue to see wide fluctuations in price as more variable weather conditions complicate prediction of demand.
As Mr corner states, the energy savings need to be considered as a whole and not just a single action, but to achieve the carbon reduction targets required to limit global warming we need to make cuts across all our activities.