Firefighters were called after a fault in a high-voltage underground electricity cable caused a small explosion in a waste sewer drain.
A total of 1,360 properties near the town centre were without power between 4.25pm and 6pm on Monday (August 4) because of the fault in the Springfield Road area.
There were further power cuts as engineers rerouted electrical supplies at 4.36pm.
A spokesman for West Sussex Fire and Rescue said the fault led to a small explosion in Spencers Road, West Green, at around 5.44pm.
A spokesman for energy suppliers UK Power Networks said: “The underground cable fault was excavated last night and repairs are progressing today.
“We thank residents for their understanding while we work to restore their electricity supplies as quickly as possible and apologise for any inconvenience caused.”