The site of the lighthouse was purchased by Trinity House in 1876 for the sum of £111, and the construction of the tower and dwellings completed the following year. In 1922 the light was converted to acetylene operation and was operated by means of a Sun Valve. This mechanism—invented by Swedish lighthouse engineer Gustaf Dalén—consists of an arrangement of reflective gold-plated copper bars supporting a suspended black rod; when lit by the sun the black rod absorbs the direct heat and that reflected from the other bars and expands downwards thereby cutting off the supply of gas.
Following the introduction of the acetylene equipment the lighthouse was demanned and the keepers’ dwellings subsequently sold in 1935.
St. Tudwal’s Lighthouse was modernised and converted to solar-powered operation in 1995. The lighthouse is now monitored and controlled from Trinity House’s Planning Centre in Harwich, Essex.