Mark Pettini's perfectly paced half-century helped Essex to top spot in the NatWest T20 Blast South Group and inflicted Somerset's fifth defeat in eight matches.
The opener contributed an unbeaten 60 to put his side well on course to overhaul their opponents' modest 150 for seven at Taunton when bad light intervened with Essex 106 for two.
After a short break, the visitors were given a revised target of 125 from 17 overs, which meant they needed 19 from 15 balls.
Ravi Bopara hit the first of them for four on his way to 33 not out and Essex breezed home by eight wickets with an over to spare. Jesse Ryder smashed 28 at the top of the innings.
Leg-spinner Max Waller was Somerset's best bowler, with figures of 1-22 from four overs. But their seamers erred on the short side as Pettini and Bopara crashed five fours apiece and Ryder bludgeoned four fours and a six.
With Hampshire losing to Surrey, victory was enough for Essex to overtake the previous leaders.
Somerset's score was built around a second-wicket stand of 80 in 9.3 overs between in-form duo Craig Kieswetter and Peter Trego after Marcus Trescothick top-edged a pull off the returning Graham Napier and was caught at deep midwicket for 16.
Kieswetter's consistency as a run-maker in T20 is incredible. He has only had one score below 37 in his last 15 innings in the domestic competition spread over two seasons.
The wicketkeeper's 40 in this game included two fours and two sixes, one of them a mighty blow over long-on off Bopara that sent the ball out of the ground.
Trego was subdued by his standards, striking four fours before being run out as he slipped when sent back by Alviro Petersen attempting a single to short fine-leg.
Essex never allowed their opponents to break free of the early grip squeezed on by Napier and David Masters.
Left-arm spinner Tim Phillips was the most economical bowler for the visitors, conceding 24 from his four overs. Petersen did his best to bolster the total with 26 off 17 balls, but 150 did not look a particularly challenging score.
After the game, Essex head coach Paul Grayson said: "Our first target is a top-four finish in the group to reach the quarter-finals. If we can achieve that and push for the top two then great because home advantage and a quarter-final tie at Chelmsford would be very special."
Kieswetter said: "For some reason we are not coming up with the right formula for T20 cricket this season. All the necessary skills are in the squad, but we are not executing them consistently enough.
"I think the bowlers are doing a good job, but we are not giving them big enough targets to defend."