About 50,000 British Gas customers have waited up to a year for electricity bills because supply companies have not developed common data standards since the market was deregulated in 1998.
The problem has left British Gas £13m out of pocket and about 10,000 customers have been waiting a year for bills. And the problem could persist, said IT experts, because it may not be cost effective for electricity supply companies to roll out the solution which being proposed by an industry body.
David Bradshaw, principal analyst at Ovum, said, "The technology does not match the requirements of the market. It is an enormous and very real problem but may well cost more to reconfigure the system than is currently being lost.
British Gas is not the only company affected by the data clashes, but it has been hit the hardest because of the size of its business.
There are 30 companies supplying electricity to consumers in the UK. Each of these employs sub-contractors to collect meter information and aggregate that data.
In all there are dozens of companies involved in the collection and holding of electricity customer data and there is no commonly agreed standard for data formats.
According to a spokeswoman for Elexon, the non-profit-making body which enforces rules for the transfer of metering data between suppliers, the volume and complexity of data is huge, especially as much of it is very old and resides in legacy systems dating from before market deregulation.
The cost and complexity involved in transferring data between these companies is huge and mismatches are usually resolved manually.
Types of data which occur include details on customers and tariffs, information on meters, the readings, meter reading history and scheduled dates for readings. Each company has different ways of rendering this information and no industry-wide standard has been agreed in the five years since deregulation.
In addition, supplier companies hold such details in a variety of architectures, including mainframes and Unix-based systems. The electricity supply industry has made no moves to harmonise conflicting technical standards.
Elexon has drawn up proposals for a "modern, simple, fast, flexible web-based universal records system to provide a transparent repository of customer information".
However, its proposal has yet to be ratified internally. It would then have to go before industry regulator Ofgem and the building of such a system would be a lengthy process.
Bradshaw said, "It is an indication of what a big problem data integration is - a far bigger problem than many people recognise. All parties to such transactions need to understand the data.
"What is needed is either a common set of definitions of services and customer details or all the parties involved to define a method of translation between the data formats used."
A British Gas spokesman said, "It is a complex system. Errors cause whole pieces of information to be stuck in the system. We are dependent on data held in old systems [at other power suppliers]. Some 50,000 customers remain unbilled, 10,000 of these for a year."