More than half a million energy customers switched supplier last month, a three-year high and 53% more than the month before.
Some 577,810 customers switched in October, and 9%, or 92,632, moved to a small supplier, the figures from Energy UK show.
Energy UK chief executive Lawrence Slade said customers were "clearly feeling more confident to switch".
He said: "It only takes a few minutes to find the right deal. More than 40 suppliers are offering many deals under £1,000, so take advantage."
Juliet Davenport, chief executive of independent supplier Good Energy, said: "I think this news is perhaps the first sign that the giant, old-fashioned energy companies are coming to an end.
"For far too long the big six have taken loyal customers for granted. Smaller suppliers are taking more customers than ever before as consumers look for better service, fairer prices and green energy."