Keith Bunce, aged 44, of no fixed abode pleaded guilty to one count of robbery at Reading Crown Court.
Bunce was sentenced to four years and six months’ imprisonment and ordered to pay £190 at the same court on 18 November.
The conviction relates to an incident in Dolphin Road, Slough on 28 September this year. The victim, a 98-year-old man, heard a knock at his front door which he ignored.
Bunce then smashed a patio door and threatened the victim, demanding money from him.
£100 in cash was taken before Bunce left the property. The victim was not injured during the incident.
Bunce was arrested on 29 September and charged on 1 October.
Designated investigator Wushma Qureshi from the Slough priority crime team said: “This was an extremely serious ordeal to have happened to a 98 year-old male in the comfort of his own home.
“The victim had previously provided the offender with money out of kindness and was repaid by having his property broken into while he watched from his armchair.
“I am satisfied with the sentence handed out to Bunce, which will give him time to think about his cowardly behaviour.
“Combatting robbery is a priority for Thames Valley Police and it will never be tolerated in our communities.”