Multiple fire crews were called just after 6.10am to Ardington Hotel in Steyne Gardens.
A spokesperson for West Sussex Fire and Rescue Service said: “Crews from Lancing, Littlehampton and Worthing were sent, as well as appliances from East Sussex Fire and Rescue Service.
“On arrival there was a fire involving the air conditioning unit and the hotel staff had carried out a full evacuation of the premises.
“Crews used one jet and one hose reel to extinguish the fire.
“There were no casualties and crews left the scene at 7.02am.”
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