Crews were called to a property on Castle Road, Bramber, shortly after 9.30pm and tackled a fire in the study at the rear of the house - three quarters of which was destroyed in the blaze.
The fire service says Tthe blaze involved an electric portable heater which had been ‘left unattended and close to combustible materials.’
At its peak, six fire engines were sent to tackle the blaze and firefighters wearing breathing apparatus used hose reels, jets and fog nails to extinguish the fire.
Station Commander Rod Gates who attended the incident said: “Despite the hard work and efforts of the crews who attended the incident, approximately three quarters of the property ended up being damaged by the fire.
“This just goes to show how dangerous heating appliances can be when not used safely.”
The fire service’s head of prevention Nicki Peddle added: “Now the weather has turned colder many people are turning to other sources of heat such as portable heaters and electric blankets to save on central heating costs.
“Last year we attended nine fires caused by electrical heating appliances. The best way to prevent this type of fire and any potential disasters is to be aware of fire risks.
“When using electric heating appliances, I would urge residents to inspect the item for damage and keep it at least a metre away from items that could catch light.
“In addition, it’s safest not to leave electrical appliances unattended when in use – even for a short period of time.”