As recommended by EECA and other agencies, here is a product that will give you very good heat retention without the huge costs associated with double glazing.
Very simple to install, 1 roll is 1.5m wide and 3m long and will cover a couple of bedroom windows on average. The kit includes the film, with one double sided tape on one side already. 1 roll of double sided tape to apply to the other 3 sides of the frame.
All you need is a pair of scissors and a hair dryer to get rid of the wrinkles.
The cost is $33.50 per roll from us.