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Updated 28 April 2013 |
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The following short articles cover a variety of topics
related to saving energy: Related pages present advice on Monitoring
Energy Usage and Smart Meters, and Saving
Energy. Energy Myths or Simple Truths? A number of common assumptions about saving energy are myths, while others
are largely true. The following examples are based on a similar list from
the National
Energy Foundation. 1. It uses less energy if you leave fluorescent or low-energy lights switched on ![]() MYTH – If you are out of a room even for
5 minutes it always saves energy to switch fluorescent or low-energy lights
off. Very frequent switching can shorten the lifetime of some low-energy bulbs,
but recent models have greatly reduced this problem. 2. It is wisest to leave your immersion heater on 24 hours a day ![]() Sometimes TRUE, sometimes a MYTH – Provided
your hot water tank is properly insulated, and no water is being
used, the tank should only cool by about one degree every few hours. This makes
very little difference to the rate of energy loss through the insulation, so
the extra cost of maintaining hot water continuously for use whenever required
is negligible. If your tank is poorly insulated (with thin foam or
a tank jacket), then switching the heater off when no hot water is likely to
be used, for example overnight, will save energy. Note that reducing the temperature
setting of the thermostat controlling the immersion heater always saves
significant energy. 3. If you have thermostatic radiator valves you don't need a room thermostat ![]() MYTH – Thermostatic radiator valves will
only switch the flow to a single radiator on or off. They do not stop the boiler
from firing and so using energy. Energy is saved if the boiler runs only when
it is needed for heating or for hot water. This requires a room thermostat.
However, the room thermostat should not be in a room which also has thermostatic
radiator valves because the room may never get hot enough to switch off the
boiler. 4. In summer it's cheaper to use an immersion heater than a boiler to heat water ![]() Usually a MYTH – Gas costs much less than
electricity providing the same energy, so a boiler would have to be very much
less efficient than an immersion heater before electricity is cheaper.
If you have a modern gas boiler controlled by a hot-water tank thermostat,
then it will be better to use the boiler all year. With oil boilers the benefits
are less but are still likely to be significant. 5. Leaving your PC screen switched on during a break prolongs its life and doesn't waste much energy ![]() Mainly a MYTH – The screen usually consumes a large fraction
of the energy used by a computer. 6. Use less power – take a shower! ![]() Sometimes TRUE, sometimes a MYTH – If your shower uses the
same source of hot water as your bath, and you use less hot water when taking
a shower, you will use less energy. However, if your shower is heated electrically
and your bath water is heated by a cheaper fuel, the shower must use considerably
less water than the bath before there is any saving. If the shower is over the
bath and you put the plug in, you can find out whether your shower actually
uses less water than the bath you might have taken. 7. Strapping on a gizmo to your boiler can save you at least 10% from your heating bills ![]() MYTH – High-pressure salesmen claim amazing improvements
in boiler efficiency if a simple device is placed around the gas pipe. Such a
major improvement would be very easy to prove in objective controlled tests from
an independent laboratory, however the salesmen will not be able to provide such
data. Instead the salesman will cite 'satisfied customers'. 8. Big freezers cost more to run than little freezers ![]() Usually TRUE, but not always – Small freezers are often upright models, which lose a significant amount of cold air whenever the door is opened. It can take as much as 30 minutes for a freezer to regain its temperature after a door has been opened for a minute. Chest freezers, with a lid opening – and typically thicker insulation – will often use less than half as much energy for a given volume of food storage. So a 125 litre upright freezer will often use more energy than a 250 litre chest model. If you have empty space in either type of freezer it's best to fill it, for example with empty cardboard boxes, to stop air flow when the door opens. Most of us are now familiar with changing our electricity supplier and many would like to sign up to a 'green' tariff (where the electricity comes from a renewable source, such as hydropower or wind turbines), but what exactly are these and are they worthwhile? There are two types of tariffs that you can sign up for: ![]()
A good source of information if you wish to switch to a green tariff is Green Electricity Marketplace. Given this confusion, if you are really concerned about making a difference we suggest that action in your own home is the best option, including anything from improved insulation or installing low-energy lighting through to installation of solar photovoltaic (PV) panels that generate electricity or heat pumps for central heating. Every action counts. Options for renewable energy generation are discussed on our domestic generation page, and grants and other financial support (such as the Feed-in Tariff and Green Deal) are described on our domestic grants page. The power supply in Blewbury should be a fairly steady 240 volts, but is often around 250 volts and has been even higher at times. Electrical equipment sold in the UK must be designed to work with voltages between 216 volts and 253 volts (i.e. 230 volts +10% and –6%). If the voltage could be reduced to say a steady 223 volts, with many devices this would reduce the energy used by nearly 14% compared with 240 volts and even more if it is higher. Some electrical equipment benefits from this, while other items do not:
The benefits can be a reduction in energy bills as well as a reduction in carbon emissions. The main disadvantages are the cost of the equipment needed, the cost of installing it, and the load taken by the voltage reduction equipment when on no load. If the standby consumption is too high this would cancel out the benefits. Apollo Enviro offers both domestic and commercial devices to optimise voltage; their website has much useful information. The VPhase product is designed for domestic use, and is expected to be fitted only on those electrical circuits where a lower voltage provides savings. Fitting will require the services of an electrician, and possibly an extra fusebox. The suppliers claim it consumes only about 6 watts in standby and can reduce total electricity consumption by about 15%. The Initiative has not tested this device. Energy saving transformers can be appropriate in industrial and commercial environments The idea is clearly relevant to industrial and commercial sites. Here the load is more continuous and may be fairly constant over 24 hours so the transformer losses at low loading are very likely to be small compared with the benefits. Also, transformers applying to a three-phase supply can achieve power smoothing and other benefits. ![]() For example it can be economic to reduce the voltage on the cooling cabinets in supermarkets. The Power Perfector is designed for such environments. A related idea suitable for industrial and commercial applications is exemplified by the Fluoresave device. This is specific to fluorescent light installations. It maintains full mains voltage when there is no load, but reduces the voltage to the lights after they have been switched on. It increases the voltage again for a time if the load changes. The physics of this device arises as fluorescent lights require a large voltage to strike the light, but then need much less voltage to maintain the plasma. |
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