RF meters, energy company's IT systems, and other assorted nonsense
In the UK, the design of the metering arrangements is such that there are a large number of companies that own the electricity and gas meters. These companies may be your supplier, the local distributor, or someone else. As such, although they could be read remotely through some sort of wireless magic, it'd still be horribly inefficient. The solution will probably come with "smart meters" (much as I hate the term), which will have remote collection (probably via GSM) as standard, with the exceptions having manual readings taken as per the current arrangements. This is broadly what happens for large (>100 kW) industrial customers at the moment - they have meter readings taken daily, broken down by individual half hours, to get a consumption profile through the day.
The software running the meter data collection algorithm was probably specced out in generic terms by someone who understands WTF is going on. In my experience, this is then taken away by a bunch of consultants (including a normally incompetent Business Analyst), and about 30 Statements of Requirements and other assorted nonsense documents will have been produced. As the consultants don't actually understand the electricity or gas industries, they'll have assumed that meter readings can only go up, and can't go down from reading to reading. Therefore, if you enter a reading of 8500 followed by 8498, it stands to reason that you've used 9998 units of gas/power.
This will, of course, have made it into the SoR that was produced, but as the only people who would spot that error are being required to review hundreds of the damn things on top of their day jobs, and because Cap Gemini, Capita, Logica, and friends tend to operate in a "if you don't make any comments of this document by noon tomorrow, we'll deem you to have accepted it" world, it's not really that surprising that something like that would get missed. As the testers are testing against the SoRs, instead of using common sense, it passes all stages of functional and non-functional testing.
Oh, and 9998 units of gas is such a ludicrously small amount in terms of the wholesale markets, (where the smallest amount of gas you can buy is 4,000 therms / 117,288 kWh over a 24 hour period), your meter wrapping around would have been a) ignored as noise, and b) wouldn't have been noticed for about 6 months, until the supplier gets round to reviewing the site's capacity.
Anonymous for obvious reasons.