In 1947 the Labour Government nationalized Renwick's power companies under the Electricity Act 1947.
[2]: 713 On 23 December 1964 he was raised to the peerage as Baron Renwick, of Coombe in the County of Surrey.
[3] Lord Renwick married, firstly, Dorothy Mary, daughter of Harold Parkes, in 1929.
He married, secondly, Joan, daughter of Sir Reginald Clarke and widow of John Ogilvie Spencer, in 1953.
He died in August 1973, aged 68, and was succeeded in his titles by his only son from his first marriage, Harry.