Episode 4 was watched by a total of 7.67 million viewers, making it BBC One's fifth most-watched broadcast of the week and thirteenth across all channels.
The figure is over 2 million higher than the initial overnight rating of 5.49 million.
The consolidated figure includes viewers who recorded the episode and watched within 7 days of transmission, but not those who viewed the programme on the BBC iPlayer (1 million) or watched a repeat showing (BBC Three - 300,000).
The Power of Three achieved an "excellent" Appreciation Index of 87.
On Saturday 29th September, the episode received its Australian TV premier on ABC1 with 565,000 viewers tuning in. It was the top rating drama of the day and the thirteenth most-watched overall. However this is only an overnight figure, which does not take regional, rural and time-shifted viewers into account.
(Source: Doctor Who News)