There are two main benefits to the consumer in choosing a dual fuel deal - price and convenience. Many suppliers offer a substantial discount to customers who choose to get both their electricity and their gas from them. Also, it can be a lot more convenient to get both electricity and gas from the same company, as you only have one bill to pay rather than two.
If your home has no gas appliances, there is no reason to go for a dual fuel deal, and you should simply search for the cheapest electricity supplier.
If you have a dual fuel account, your energy supplier may still bill you separately for your electricity and gas bills. This makes things a lot tidier if you switch suppliers, as you can keep your past gas and electric bills separate. Some dual fuel suppliers will combine your monthly gas and electricity usage into one simple monthly fuel bill.
While you can pay for your separate fuels using different payment methods in a duel fuel contract, without losing any of the cost benefits of such an arrangements, this is markedly less convenient than paying both the same way.
Dual fuel policies definitely help to keep things simple, and while most companies offer dual fuel discounts, these deals are by no means always the cheapest on the market. If you are on the lookout for the most economic deal possible, then its worth checking the prices of single fuel tariffs too.
One of the drawbacks of dual fuel contracts is that if you get behind with your payments for either of your utilities, you run the risk of having them both cut off by the one company. However, the suppliers are obliged by law to offer some support to those who can't pay their bills. However, if you find yourself having to come to an arrangement with your supplier, you may find it a lot harder to switch suppliers while you owe your existing supplier money.