Flow Energy has confirmed it's set to increase the cost of its standard tariff by 10% from 1 September, adding an extra £95/year to a typical household's dual-fuel bill.
This will increase the bills of those with a standard variable dual-fuel tariff to an average £1,044/yr up from £949/yr.
The medium-sized supplier which has about 170,000 customers has been writing to everyone affected over the last few weeks.
The news from Flow Energy comes hot on the heels of British Gas's price hike, announced on Tuesday. Two hefty price rises in short succession could raise concerns we'll see another batch of energy hikes this winter.
How does this affect Flow Energy customers?
Flow Energy's standard variable prices are due to rise by 10% across the board so whether you've dual, gas or electric-only, bills are set to rise at the same rate.
If you're on a fix you won't immediately be affected by the price hikes, as your rate is locked in but make sure to check when your deal ends so you're not rolled onto its standard tariff.
If you're within 49 days of your fix ending, you're free to switch away to another tariff or provider without paying exit fees, under rules from regulator Ofgem.
What does Flow Energy say?
Andrew Beasley, managing director of Flow Energy, said: "Flow has historically had a low standard variable tariff. In fact, for some time we had no price difference between our variable and our competitive leading tariff. However, over time, as the market has moved, we've had to increase our variable costs.
"We don't like doing this but we've tried to keep the increase as small as possible and we still have lower variable prices than many of our medium-sized and large competitors. We've written to all our variable customers offering them the chance to switch to a cheaper, fixed-rate tariff."