Is it true that you use more energy to turn lights on and off than leaving them running?

There is a widely held belief that it is better to leave fluorescent lights (like energy saving light bulbs) on rather than switching them off. It is true that they draw more power when they are warming up however this only takes a few seconds at most so is equivalent to a couple of minutes electricity use when they are on and it is best to keep them switched off when they are not needed otherwise you are wasting money and energy.

Use less power - take a shower!

It is not a simple question if showers are better than baths, particularly if you have a power shower! If you want to check the difference in the amount of water used, put the plug in the bath next time you have a shower, and see how much it fills up. If, at the end of the shower, there is less water than you would usually have in a bath, then you will probably save money by taking a shower. Also bear in mind that a unit of electricity costs more than a unit of gas if you are comparing an electric shower with bath water heated by gas.

It is best to leave your immersion heater on 24 hours a day

It is always best to place the water heating on a timer. It's a common myth that it takes more energy to keep heating up a tank than to maintain it at a high temperature. Unless you have a need for large quantities of hot water all day long it is much better to install a timer. A timer suitable for immersion heaters should cost less than £20 and could pay for itself in a few months.

If you have Thermostatic Radiator Valves you do not need a Room Thermostat.

Thermostatic Radiator Valves (TRVs) will only switch the flow to a single radiator on or off. They do not stop the boiler from firing (and so using energy). They are useful, but tend to be a rather crude control of temperature in a room. TRVs can also be affected by having furniture in front of radiators and are often not set at the right temperature. In contrast a room thermostat is accurate to within a degree or so. What's more, if it has been wired up correctly it should send a signal back to the boiler to switch itself off if there is no demand for heating for either the heating or hot water circuits.

Leaving your PC screen switched on when you are not using it prolongs its life and doesn't waste much energy

Leaving the screen may prolong the life in theory, but in practice how many PC screens are thrown away because they have broken down, and how many because they have become superseded by more modern technology? With typical CRT monitors using 95W to run and 15W in standby, and flat screens using 40W to run and 5W in standby, switching off really does save energy and money. Screens do not use less energy when they are in screen saver mode (designed to stop the phosphor coating being damaged), and even when they power down into sleep mode (typically after more than 20 minutes) they still use some energy.