Gas dryer v Electric dryer the facts
Gas Powered Tumble Dryers
Tumble-dryers dry clothes by heating them in a drum which is slowly rotated. A common electric tumble dryer uses an electric heating element to warm up the clothes, whereas a gas tumble dryer burns natural gas (mains gas not LPG). Although electricity is still used to rotate the drum, this amounts to less than 10% of the total electricity used by an electric tumble dryer - the remaining 90%+ all goes on heating.
Since using gas for heating is more energy efficient than using electricity (hence the use of gas in all the latest boilers), the financial costs of running a gas tumble dryer are lower than those associated with an electric tumble dryer - typically 1/2 to 1/3 lower. Also the carbon emissions for gas are around 0.193 kg / kWh (unit) compared to 0.432 kg / kWh for electricity - i.e. emissions are more than halved with a gas tumble dryer.
Disadvantages of Gas Tumble Dryers
An electric tumble dryer can easily be installed as a DIY job - particularly condenser dryers which just need plugging in. Gas tumble dryers must be installed by a Gas Safe registered gas fitter (in the UK), and any maintenance will require a similarly qualified person. Also, there are no gas powered condenser dryers available since all gas tumble dryers must be air-vented anyway. This means that a hole must be made through an exterior wall if one is not already there.
Natural gas is a finite resource - perhaps only lasting another 30-50 years - and it is a fossil fuel. One advantage of an electric tumble dryer is that it can be powered using renewably generated electricty - not an option with a gas powered tumble dryer.