The main reason online-only banks are able to offer better prices than their high street rivals is the lack of "bricks and mortar" - the expensive branches big banks have spent centuries building up.

But internet banking comes with its own cost, and it can be hefty: buying a computer. This should change as Wap-enabled mobile phones and digital television become more common, but for now for almost all e-banking customers need access to a computer. Worse, not all expensive computers will do so picking the right machine - or, for people who already own one, the right bank - is important.

"I spent ages trying to get it to work only to find it wasn't compatible," complained one frustrated would-be Smile customer. Because he owned an Apple Macintosh, the service would not work. Smile says it is working to fix the problem, and some older Macs can access the system. But the problem is a common one, with RBS and NatWest also involved in making their systems compatible with Macs.

Some banks are even more restrictive. Royal Bank of Scotland requires users to have Internet Explorer, the browser software from Microsoft, running under Windows on a PC - so excluding all users of rival software Netscape and anyone choosing Macs or other operating systems such as the increasingly common Linux.

Mac users will find they can access many of the banks, including Barclays, but until they try other services with their particular computer configuration it can be difficult to tell whether they will work. All the banks set out the requirements for their services on their websites.

Customers who happily get by using a computer from the last century need not despair, as direct-dial computer services, not using the internet, are still available from Bank of Scotland and Nationwide. But of necessity these are less flexible and you can only use the computer on which the software has been installed. Internet banking allows access from any machine connected to the web, enabling people on business trips or holiday to manage their money.

Banking on the move

Mobile banking, using the screen of the new generation of mobile telephones, is set to become widely available later in the year, cutting out the need for a computer.

A primitive online banking service is available from almost all mobiles to First Direct customers, using the short messaging service - but this does not allow money to be moved around because it is not secure enough.

Some of the e-banks, including Woolwich and Egg, already offer their customers secure account access through the tiny screens of a mobile, using wireless application protocol (Wap), to access the internet. The price of these phones is falling rapidly, and several banks are giving away or heavily subsidising the price of the handsets in order to increase the number of users.

For now Wap technology remains slow and prone to problems. In the autumn, however, a new, faster system will be introduced that should allow permanent connections to the internet, eliminating the slow connection times. The banks hope this will also make it quicker for customers to check a balance on the telephone screen than to telephone the bank and ask an operator what their balance is, bringing electronic banking to the millions of people who have a mobile phone but no computer.

Sofa so good?

The other big technological development under way at the moment is television banking. Nicknamed "sofa banking" because consumers sit in their lounges and control their finances by remote control, this has been pioneered by HSBC with its Open service. But Abbey National is investing heavily and most of the big banks - as well as smaller banks and building societies, including the Newcastle - are likely to offer services shortly.

The service operates through digital television, and at the moment only subscribers to cable or satellite digital television, not terrestrial, can bank through the remote control. However, the number of people with digital access is expected to grow rapidly and the government has pledged to turn off the standard analogue signal, forcing everyone to upgrade to digital, in ten years.

The services available through digital television are currently limited, with only Abbey National and HSBC going beyond basic loan calculators and marketing. But the banks will be upgrading their systems to provide all the facilities of internet banking, together with the snazzy video and music made possible by the television. The lower-quality screen of televisions, and the limited control the remote provides, mean the experience is likely to be quite different to internet banking, though, with less text and more pictures and sound.

Banks have high hopes for television, as they expect viewers to apply for personal loans or ask for information on mortgages in the advertising breaks of Coronation Street, bringing the bank manager into the living room. Whether viewers will want to think about finance while relaxing with their family has yet to be tested.