New rules mean that energy companies must now inform consumers of any price rises at least 30 days before the increase, rather than leaving it up to two months after the changes.
The changes were put in by regulator Ofgem on Thursday, stripping energy suppliers of previous rules that allowed them to withhold information about price rises until up to 65 working days after they came into force.
The new rule also means that suppliers must inform customers of any changes to a contract that might leave them significantly worse off.
The 65 day notification period was originally designed to make people aware of changes, rather than relying on them to notice an increase in their bills.
After customers were notified of the changes they were given 20 days to switch supplier in order to avoid paying the higher price. Under the new rules, customer can switch before the increase comes into effect.
Ofgem’s senior partner for markets, Andrew Wright said: “Ofgem is determined to ensure that supply companies play it straight with consumers. Giving customers advance warning of price rises is one way of ensuring a fairer deal for them”.
Campaigners have responded to the news, calling it “long overdue”.