Storm windows cost far more to replace than to repair, unless the damage to the existing structure has made the repair uneconomical. In any case, either repair or replacement will be cheaper than the alternative of having the entire window set up completely replaced with new energy efficient windows. One of the greatest advantages of storm windows is that they are financially viable for the vast majority of households, giving everyone the chance to save money on their heating bills.
The relatively low cost of storm windows is one of the reasons why they retain their popularity in an era where there are more effective alternatives. There is no doubt that if you want the most effective solution to the problem of insulating your home, you will find it in having completely new external windows fitted, made from new energy efficient materials. You can even claim tax credits to help with the installation of these windows, adding further to the savings. However, the expense involved in having the installation carried out in the first place, combined with the inconvenience of having such major work done, often means that the project is not viable.
If you have decided that storm windows are definitely the answer for your room, the net step will be to decide on materials and on the way you want them to fit. Storm windows can be either external or internal, and there are definite advantages either way. An external storm window will cover the existing window on the outside and increase its life span dramatically, and it will also help to cut out a lot of the ambient noise from outside. A window fitted in this way will need to be able to withstand everything the elements can throw at it, and with a safety margin built in as well.
Most storm windows are fitted internally, and typically these storm windows cost less than those fitted externally because they do not need to be so hard wearing. This cost can be reduced by using cheap materials and fittings, but the economy is likely to be a false one as these will not be effective in eliminating drafts and allowing you to reduce the settings on your heating system. Buying a better quality window in the first place will always pay off, even with an internal storm window.
A quick analysis of storm windows prices will reveal that quality materials have a necessarily higher cost, but that they are more likely to pay for themselves in time. Reduction in drafts with windows which are soundproof is far greater than for standard storm windows, so they will allow you to turn your heating level down. In cold climates, this will be felt even more strongly. There will be several side benefits as well, such as a decrease in the amount of ultraviolet light and noise which are allowed into the room. This will keep living conditions far more pleasant, irrespective of the savings.
It could even be said that cheap storm windows cost more in the end, because they do not do anywhere near as effective a job, but of course everything is relative. It is impossible to put exact numbers on any individual case, because each household is different. Heating is used at different rates as people spend more or less time in the houses, older and infirm people need the temperature at a higher level in any case, and each climate is different. Even houses in the same street can react completely differently depending on whether they face North or South. It is really impossible to know whether an individual household can justify the storm windows cost.