Drying clothes in the open air is obviously the most energy-efficient option as it requires no electricity at all. Unfortunately it isn’t always possible due to the weather, to available space and of course to busy lifestyles.

The alternatives are to dry it in the air in the room, either on a frame or radiator, or to use a tumble-dryer.

If the radiators have to be put on specially to dry the clothes then there is a cost for running them. A typical 1m wide 600mm high double radiator produces around 2kW of heat. Assuming that two radiators are needed running for two hours to dry a full load, they would use about 8kWh of heat — and probably make the room quite steamy and unpleasant as well as making some of the clothes as stiff as boards. Drying clothes on radiators is not recommended as it can lead to damp and rot in the building.

By contrast an ‘A’ rated tumble dryer is likely to use less than 2kWh/cycle1, will leave the clothes easy to iron, and the room free of steam and condensation.

To achieve ultimate savings in energy-use old inefficient models should be replaced by new high performing models.  In a real–life pilot study an A++ tumble dryer saved 39% energy when it replaced a 5-10 year old model.

There are three types of tumble dryers available on the market. Advances in modern technology mean new models use less energy with varying degrees of success, explained below:

1) Electric vented dryers – draw air in from around them and heat it before passing it through the clothes. The resulting hot, humid air is usually vented outside so as to avoid problems of condensation in the property.

Vented tumble dryers score poorly because the energy consumption calculations take into consideration any extra central  heating that will be required to replace the warm air lost to the outside in the venting process.

2) Condenser dryers – pass air through the clothes but instead of exhausting this uses a heat exchanger to cool the air and condense the water vapour.  The air is then re-heated and re-circulated back through the clothes.  The condensed water vapour is either collected in a water bottle or pumped into a drain.

Heat pump dryers – are a type of condenser dryer which uses a heat pump system and a heat exchanger.  Because the heat recovered from the heat exchanger is reused to heat the air before it is passed back through the clothes less energy is needed for heating.

Heat pump dryers are more energy efficient than traditional vented or condenser dryers but they are relatively expensive.

The disadvantage of condenser and heat pump dryers is that the water has to be removed either manually from a tank or by providing a connection to drainage. Available connections to vent or drainage and the inconvenience of emptying the water tank have to be considered when making a decision on which appliance to purchase.

3) Gas powered dryers – using  a primary fuel they are often seen as more energy efficient than equivalent electric dryers.  They do, of course, have to be connected by a Gas Safe Registered installer but the costs of this may be offset by their lower running costs. Under the new energy labelling scheme, gas dryers are allowed to be labelled for the first time marking a  shift from the emphasis on electricity.