Margaretta Lewis, 87, from Worthing in Sussex, was checking for noise coming from a recently repaired radiator when it fell off its brackets and pinned her to the floor.
She was knocked unconscious for several hours, suffered a fractured hip, broken ankle and received severe burns to her legs as the radiator remained on throughout her ordeal.
She was only discovered the following day when she was visited by social services and Meals on Wheels.
A report commissioned by solicitor Richard Biggs, from law firm Ralli, said Worthing based Chris Fosbury Electrical had failed to fix the radiator properly to the wall and had used screws which were too small for the weight of the device.
Mr Fosbury’s insurance company accepted liability on his behalf and agreed an out of court settlement.
Mr Biggs said: “There was a real moral principle behind this case. Somebody had failed in their professional duty and my poor client suffered horrendously as a result.
“This was a shocking case and I hope the outcome sends out a clear message – especially to those installing heating systems for elderly and vulnerable people who may not be aware of the standards to expect. This was a horrific incident and she is lucky to be alive.”
Mrs Lewis, whose husband was killed in World War II, still suffers from debilitating vertigo.
She said: “It was a horrible experience. I felt so helpless and thought I was going to die. I’ll never forget the relief when they lifted the radiator of my legs.”