How low can the temperature go in an unheated but insulated cabin in order to damage LCD TV, phone, and computer?

I’m asking for a friend. The cabin is 12’ x 14’, unplumbed, raised but no foundation and has some windows that will provide a little passive solar heat, if there is sun. Winters here are severe, can get down to below 0˚. Pitched insulated roof and a dropped beaverboard ceiling. Owner uses it only on week-ends for a few hours and will be away for Dec- April. Lots of snow. He will use an electric portable heater. Throw rugs but bare floor.