EDF is to cut variable gas prices by 5.2% from January and freeze variable electricity costs until March before an 8.4% rise.
EDF pre-payment gas customers will get a 12.9% cut for three months from January before a price cap recommended by the Competition and Markets Authority takes effect.
The changes mean that the energy-giant's new standard dual fuel direct debit price will increase by 1.2% to £1,082 a year.
The variable gas price cut will affect 700,000 customers, while 200,000 pre-payment gas customers will benefit from the three-month cut from January.
French-owned EDF said electricity costs have been rising, but gas prices are not facing the same pressures.
Beatrice Bigois, managing director of customers at EDF Energy, said: "We want to help loyal customers by cutting gas prices ahead of the coldest winter months, and delaying electricity increases until later in the year. This will save customers money this winter.
"Gas pre-payment customers on our variable tariffs will also benefit three months ahead of the price cap being introduced following the Competition and Markets Authority investigation.
"Many industry commentators have said that prices charged by energy suppliers will rise after the winter. We are being open about the fact our electricity prices will go up after our price freeze. But we also know it is right to pass on to loyal customers the fall in gas costs that energy suppliers have seen over recent months."
Around 1.5 million EDF customers, or 44% of the total, are on fixed tariffs and so will not be affected by the price changes.
In a statement EDF said: "Since the last electricity price change over three years ago, a number of electricity costs have risen substantially.
"EDF Energy has worked hard to limit the impact of these costs for customers through efficiency savings across the business, whilst its responsible policy of buying energy ahead of time has protected customers from the more recent volatility in wholesale energy costs.
"However non-wholesale energy costs have risen to ensure reliable supply though investment including in networks, renewables and metering."