The Big Six energy companies have faired badly in the latest annual Which? energy company satisfaction, for the fourth year running.
The smaller suppliers took the top spots, Ecotricity came 1st, with Good Energy, Ebico and Ovo Energy closely behind.
npower came lowest with only 35% with consumers rating it the worst for complaint handling and customer service.
It was followed by ScottishPower, EDF Energy, British Gas, E.ON and SSE.
Richard Lloyd, Which? Executive Director said: “For the fourth year running, smaller suppliers are wiping the floor with the Big Six on customer service. The large energy firms, which dominate the market, need to up their game as millions of customers deserve better.”
The overall customer score for energy companies has however improved from 41% last year to 48%, the survey of more than 9,000 adults found.
Energy UK said customer service is a “key priority” for energy firms.
A spokesperson added: “Change takes time in an industry as large as the energy sector.
“No one wants to see complaints and most are dealt with by the end of the next working day with no more than a phone call. The majority of queries relate to billing issues, a problem that will be significantly reduced with the roll-out of smart meters.”