At last, there is some good news on gas and electricity billing and prices - although it won't affect all customers equally, and will be offset for some by more bad tidings on their supplier's service performance.

Earlier this month, regulator Ofgem introduced a ban on the type of complex power tariffs that made it impossible to work out whether it was worth switching to another provider.

It described the move as making "the biggest changes to the retail energy market since competition was introduced in the late 1990s".

From January 2, suppliers were no longer allowed to offer complicated tariffs, such as those where the rate charged fell as power use increased.

Now, once a customer has chosen their supplier and payment method, they can be presented with a choice of no more than four gas tariffs and four for electricity.

And there are more changes to come. From April, suppliers will have to tell consumers on bills, annual statements and other communications which of their tariffs is cheapest for them.

However, Gillian Guy, chief executive of Citizens Advice, cautioned: "It is important energy firms use this as an opportunity to regain customers' trust by laying out a fair set of tariffs. It should not be used as a chance to get rid of cheaper deals."

The major providers' responses to the Government's recent reduction in the green levy it charges power companies offer limited hope on this score.

The Big Six - ScottishPower, SSE, npower, British Gas, E.ON and EDF Energy - have all made announcements on how this will affect prices.

Price comparison website uSwitch.com says their cuts average 3%, or £40 a year, for the typical user, and implementation dates range from January 1 to March 24.

According to the site, the average annual dual-fuel bill has risen from £1212 to £1281 over the past few weeks, thanks to price rises by the Big Six.

Once the green levy changes take effect, it will fall to £1264, meaning the typical consumer is still paying £52 more than a couple of months ago - and a staggering £792 more than in 2004, when the average annual bill was just £472.

And consumers won't all gain equally from the levy reduction.

Clare Francis, editor-in-chief at price comparison site MoneySupermarket.com, explained: "Customers of npower, ScottishPower, EDF Energy and E.ON who have fixed-rate deals will only receive a £12 rebate from changes to the Warm Home Discount Scheme. They won't benefit from the cut in green levies."

All SSE customers will benefit, but not until March 24. Only British Gas has passed on the benefit to all customers immediately.

The Big Six have said they will now hold their prices until sometime in 2015, but most have added the caveat that if wholesale prices or other costs rise substantially for a sustained period, they may go back on this.

Meanwhile, this week brought more bad news for npower, after it struck a deal last month to pay £3.5 million to help vulnerable consumers following an Ofgem investigation into its sales practices.

Data compiled by watchdog Consumer Futures shows it received around eight times more customer complaints than the best performing company between July and September last year. SSE had the fewest, followed by ScottishPower, British Gas, E.ON and EDF.

Ms Guy said the findings "should serve as a stark reminder to energy firms that there is much more for them to do in order to improve service and increase consumer trust".

Ann Robinson, uSwitch.com's director of consumer policy, said: "There is only so much the government has been able to do to help consumers - it's now time for consumers to help themselves. There is £274 difference between the cheapest and most expensive (average) tariffs on the market, which means there is significant scope for consumers to give themselves a real price cut by shopping around and, particularly, looking at what small suppliers have to offer."