Keeping orchids alive in Canberra's winter can be challenging. The easiest and cheapest way is to grow orchids that are cold tolerant, such as native terrestrials and some exotics such as Bletilla striata and Vanda falcata.
It is sometimes possible to find warmer sheltered positions in your garden and here there is scope to grow various native orchids, such as thelychitons. North facing brick walls with eaves can provide some cold protection. Elevating the plants may also provide a warmer situation. Use of simple frames with frost cloth covering can be quite effective in protecting more cold tolerant orchids.
However for many of the more exotic orchids some form of greenhouse with heating is essential.
Click here for information on heating prepared by Jane Wright. Prices quoted in the document were at April 2019.