A fire which destroyed a homestead near Raglan this morning was caused by an overloaded multiple electrical socket in the kitchen.

A 76-year-old woman who was alone in the rural Wainui Rd house woke to the heat coming from the kitchen about 1.30am today.

Raglan fire chief Kevin Holmes said she noticed there was a fire and walked into the kitchen to see flames.

"She said the heat woke her up."

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Her son's family lived about 50m and her grandson heard his grandmother yelling from the house.

The woman's son and grandson ran up to the house to find her still in the house.

"Whether she was confused, we don't know," Holmes said.

"It was just getting established. He son tried to chuck water on it but it had no affect. All they could do was grab her and it just took off."

The three family members escaped the house just as the fire engulfed.

The grandmother is being treated at Waikato Hospital for smoke inhalation.

Fire Service northern communications shift manager Colin Underdown said the home in the coastal Waikato community was well ablaze by the time firefighters arrived.

Two fire trucks and a tanker arrived shortly after 1.30am.

St John Ambulance said one person suffering from smoke inhalation was taken to Waikato Hospital with moderate injuries.

Fire safety officers were expected back at the damaged home this morning to determine the cause of the blaze.