The manufacturer description is accurate in theory. It will reflect about 90% of the heat back into the house. However, if you consider that only 30% of the heat is the 'radiation heat' (the rest being convective) and that there are two sides to a radiator, the reflected heat will be 90% of the 15%. This will work out to about 13% of the total heat. Add to this that the way this item is hung between the radiator fixings to the wall, only about two thirds of the rear of the radiator area is covered. Also, these are only going to be maximally useful in radiators attached to the periphery walls. As mentioned by other reviewers, the area covered depends upon the radiator size. A 20 radiator pack will cover about 6 standard radiators and 6 large radiators. The cost saving is only for the peripheral wall radiators which may account for about 50% of total. Taking all this into account, the panels might make some difference but to recover the cost may take at least a couple of years. The product itself is something like a very thick kitchen foil (claimed to be from a specialist material unlike the foils). Installation is very easy. The printed lines on one side of the foils helps to cut the sheets accurately where required. I bought them to avoid the hassle of sticking the foils on the wall. When cut as per instructions, the foils are hidden from view. If you have some foil spare, use it for the garage floor! Overall the product is not bad but I am not sure whether it will make any huge difference. At the least, I feel happy that I am contributing to reduce my carbon footprint. Everything else is a bonus.