More than half the households in Wales do not trust any energy supplier, new figures show.
The lack of trust was greatest among low income groups, but was lower amongst those who have a smart meter.
More than a third of people said they were concerned their energy bills were not accurate, the Smart Meter Central Delivery Body (SMCDB) poll found.
About 35% of residents said they did not understand their bills and 37% did not know how much they pay.
The survey, carried out ahead of next year's planned roll-out of energy smart meters across the UK, also revealed 40% were not confident they had enough information to select the right supplier.
Once installed, smart meters will show exactly how much gas and electricity is being used and its cost.
The programme is in its early stages but more than two fifths of bill payers have expressed an interest in having a one installed.
A spokeswoman for energy provider SSE, whose companies include Swalec, said it knew it needed to work hard to rebuild the trust of its customers.
"This research shows that having a smart meter helps increase a customer's trust in their energy supplier, so suppliers and the SMCDB alike should be focusing their efforts on exciting people about getting a smart meter," the spokeswoman added.
"At SWALEC we are completely focused on delivering the roll-out as cost-effectively and as seamlessly as possible for customers."