A young Londoner is very serious about the green lifestyle.

He has been living in a tree house in the English countryside for six months and he catches his own food from the forest.

Nick Weston, 27, is trying to live as self-sufficiently as possible. He grows his own vegetables, catches fish from the local river and hunts for his meat. […]

He has no electricity, but uses solar power to charge his mobile phone and has a wind-up radio. […]

He admits that he still tries to switch on the light when he goes into his tree house because the habit is so ingrained. Everything takes a long time in the forest – dinner preparations start around mid-afternoon if he wants to eat by 10pm and even making a cup of tea is time-consuming.

[…]

Source: Speak Up, ano XXIII, n.277, September 2010, Editora Rickdan, p. 32.

In the sentence “He admits that he still tries to switch on the light when he goes into his tree house because the habit is so ingrained”, the verb switch on means: