The trio of intruders are believed to be the same suspects who had been seen wielding weapons at another property on the same night.
Officers are appealing for information after the two aggravated burglaries in Hornbeam Road, Northolt.
A Metropolitan Police Service statement read: “In the first incident, three suspects broke into a property and stole money while the occupants were asleep upstairs. A quantity of cash was stolen.
“In the second incident at a neighbouring home, the trio broke in but woke the occupant. He confronted them, chased them out of his house and smashed the rear window of their getaway car, which was later identified as a pale blue Citroen C3.
“Officers from Ealing CID are appealing for witnesses and information, in particular from anyone who may have seen the damaged Citroen or carried out repairs to the rear window.”
Both crimes took place in the early hours of the morning of 30 December but details were only released this afternoon.
Anyone with information is asked to call DC Nicholas Strachan at Ealing CID on 101.
To give information anonymously contact Crimestoppers on 0800 555 111 or visit the crimestoppers-uk.org website.