Calculating the return on investment can be difficult, as it depends on a number of factors –the efficiency source, variations in prices, the energy needs and the energy-efficiency of other components in the house. We must also remember any financial incentives received, upon installation.
Putting this into context, savings equate to between 5-10% of your energy bill. The average electricity bill in South Australia in 2018 was $2300 so assuming you save the maximum 10% of your heating and cooling costs, you should save approximately $230 each year. If it cost about $10,000 to install the windows, the investment will payback in about 40 years.
Replacing your windows with double glazing just to save money doesn’t make too much sense. Yes, you’ll reduce heat flow through the windows, assuming this is the only insulation you have installed but there are other benefits too… getting rid of those constant drafts, being more comfortable, better acoustics, less maintenance and doing something for the environment.
Choosing a less efficient type of glass would mean lower savings and reduced financial incentive – compared to installing double glazing which is seen as a property investment. The most energy efficient houses have higher value and greater marketability, so it pays to make the switch.