Tens of thousands of energy users will no longer have to pay up to £900 each if they are forced to have a pre-payment meter installed.
From January, energy regulator Ofgem is to set a maximum charge of £150 in such cases.
The most vulnerable will see their charges waived completely.
At the moment about 40,000 people a year are obliged to pay large fees when their energy supplier gets a court warrant to have a meter put in.
On average, customers have to pay £400 to cover the costs of the installation.
Such costs include court fees, and the use of locksmiths or dog-handlers, if these are needed.
However, some energy firms already supply such meters for free.
Those who will not have to pay anything include people in “severe” financial difficulty, or those who would find the experience “severely traumatic”, for example, due to mental health issues.
Those who are forced to have pre-payment meters installed are frequently in debt in the first place – making it difficult for them to pay the extra charges.
“At the moment vulnerable customers face a double blow when they’re hit with high warrant charges on top of existing debt – risking making their situations worse,” said Rachel Fletcher, Ofgem’s senior partner for consumers and competition.
“The measures will protect all consumers, including the most vulnerable, from experiencing unnecessary hardship due to having a meter installed under warrant.”
Ofgem also warned suppliers that installing pre-payment meters should be a last resort.
Customers should instead be encouraged to manage their debt through repayment plans.
Since April, the price of energy for pre-payment meter customers has also been capped.