It's mid-September and according to the Energy Saving Trust, almost half of households will already have their heating switched on by this time of year.

It's easy to see why - it suddenly feels colder, darker and rainier, just a few weeks after we were all enjoying a summer of heatwaves. But with the return of the heating comes the return of higher energy bills, and they'll be going up again in October.

According to experts, there is a way to reduce your energy bills this winter, by using cling film.

The seethrough plastic wrapping is more commonly used to wrap up food leftovers, but apparently it can double up as a cheap insulator for windows, which are one of the most common sources of heat loss in the home.

Martin Lewis' MSE explains: "Although cling film is normally used to wrap up your sandwiches, it may actually help keep your home warm too.

"Although not technically cling film, the Centre for Sustainable Energy suggests covering windows with a thin transparent plastic film, which looks like cling film, and you can install yourself.

"It's cheap and simple, and by putting a sheet of specifically designed film (or good old fashioned cling film) on each of your windows, you trap a small layer of air, which can help to stop heat from escaping. The key for adding a second layer of 'glazing' is that it's transparent and airtight."

The tip is backed by window firm Everest, which says: "When the cold snap happens each year, keeping warm in our homes becomes a priority. With Ofgem price caps soaring over the last few years, and with the pressing issue of climate change, there has never been a greater need to be more energy efficient.

"Windows contribute 20% of heat loss from a room, so any small changes you can make to insulate windows will have an impact on your energy bills and the comfort of your home.

"For the 80% of homes that have double glazing, upgrading to ultra-efficient triple glazing can be three times more energy efficient than if the windows are old double glazing. But currently, only approximately 0.17% of homes in the UK are taking advantage of triple glazed windows.

"For anyone who isn't ready to invest in replacing their windows, there are several things that can be done to help save money and keep warm.

"Insulating your windows can help to reduce how much energy is lost through the window and keep rooms at a healthy temperature without costing a fortune.

"Reducing heat escaping through a window can be best achieved by adding barriers and there are several ways to do this."

As well as the usual tips like using curtains and blinds, and sealing gaps around windows, Everest says that proper window film does work.

Its guidance adds: "Window film is effectively like a thick cling film wrap for windows.

"A window film kit typically includes a plastic shrink film that's applied to the indoor window frame with double-sided tape. After installation, you use a hair dryer to shrink the film, removing wrinkles and creating an airtight barrier.

"The film creates an insulating barrier, reducing heat loss. It's claimed that a quality window film can reflect up to 30% of the room's heat back into the room in the winter. Although cheap film kits are probably less than this.

"For a quick and relatively cheap solution to provide extra window insulation, this is well worth considering."