According to West Sussex and Fire Rescue service, crews were called to assist UK Power Networks after a 'small fire' broke out in an electrical sub station in South Street, Worthing.
Montague Quarter Shopping Centre was reportedly out of power, while residents in Liverpool Road and Alexander Terrace also reportedly affected.
A fire service spokesman said: "A call came in to us just after 9pm.
"The electricity was isolated and left with UK Power Networks [to deal with].
"All crews left at 12.30am."
On its website, UK Power Networks said its first call came in at 7pm and said the issue was traced back to a 'fault on an underground electricity cable affecting the local area'.
The electricity provider said power was restored shortly by 1.30am.
A spokesman added: "Our engineers worked as quickly and safely as possible to restore electricity to 20 properties in Worthing, which were affected by a power cut.
"All customers had power restored by 1.30am this morning. We realise how difficult it can be without power and apologise for any inconvenience caused."