Around 500 EDF energy workers struck at sites in London and across southern and western England on Wednesday of last week.
The Unite union members are fighting attacks on their pay and conditions.
Bosses’ plans to roll out new smart meters would mean longer hours, the threat of job losses and pay cuts of up to £6,000 a year.
Around 40 workers rallied outside the EDF site in Bromley in south east London.
Unite rep Steve Ricket told Socialist Worker, “They just reneged on our agreement.
“It means guys who’ve worked here over 30 years are suddenly being told they have to work early mornings, evenings and weekends.”
Union officer Onay Kasab said longer strikes could be necessary to win.
Picket Mike said, “Rather than one-day strikes I’d want to do walkouts of a number of days together—I think that’s more effective.”