If we all make a small saving it will make a large difference.
No, that will make a small difference 🙂
Small changes could only make large changes is we thought that Chaos theory could be applied. In that case “making a small saving may make a large difference” could have been used.
For a more rational assessment of energy policy you can look at David MacKays book, in which he uses numbers to examine the problems of supplying sustainable energy to the UK. The book can be found online at http://www.withouthotair.com/.
One way to save a little energy may be to use LED lighting as developed by Prof. Colin Humphreys. Which you can read about in the EPSRC press release
Low–Cost LEDs to Slash Household Electric Bills. This can save energy in cases where household heating is supplied by Gas, or perhaps by heat exchangers (tungsten filament light bulbs also provide heating which may or may not be regarded as wasteful).