This is one of the most highly debated questions in the industry. The only way to tell what performance you are going to get out of a heater is through a certified spectral analysis. Unfortunately, most companies do not publish this information or some that do put up false documents to give the customer the illusion they are buying a quality product. We are one of the only companies on the market to actually test and publish our data....that's why the doctors love us. View Spectral Analysis Please see the Buyers Guide for much more detail on how to spot good quality vs poor quality.