The two reasons for this are:
- My house has about 20 lights in it. At an average of 60w per bulb (for conventional bulbs) this is only 1.2 Kw. My shower is 7 Kw and my oven is 4 Kw. My kettle is 1.2 Kw. My fridge is a few hundred watts but it runs all the time. These larger appliances compose a larger part of a household power bill than the lighting does. Reducing the use of these will have more impact on bills than reducing the current consumption of household lighting.
- Low energy bulbs produce less heat than conventional tungsten bulbs. This means that if you switch to low energy bulbs, but have thermostatically controlled heating it will run slightly harder to make up for the loss of heat from the bulbs.
Having said this, the low energy bulbs do have a number of advantages, especially their life which means that I rarely need to take an enclosed light fitting apart to fit a new bulb.
The way to save power is probably to reduce the use of high power appliances and switch things off when they are not in use.
Feel free to comment.