If you read the report correctly and see who carried it out it was University of Ulster. As part of a Knowledge Transfer Partnership, Copper Industries assigned the graduate the task of carrying out unbiased tests on both materials. If ever you needed written proof of something this is it.
That seems quite a long time considering the size of heat pump. Next time try a copper tank with 3m sq of highly efficient integron coil and see how you get on. Probably heat up more than 28.8% mroe efficiently, considering the copper tank has a superior coil.
All our copper unvented comes with a 25 year gaurantee and massive numbers of copper tanks will out live this, and have done! Stainless steel is so new to the market no-one knows how long it will last.
Copper tanks have been around in Guernsey for years and still going strong. As I have said copper will form a biofilm which protects from the aggressive content in the water. We use 1.8mm gauge copper for our unvented which is plenty heavy enough...compared to 0.55mm stainless steel as many of the manufacturers use.
Stainless steel is more suitable for the job when higher pressures are involved and there is a tight budget to stick to. if you want to best hot water tank stick with the tried and tested material, Copper.
