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 Unfortunately, most companies do not publish this information or some that do put up false documents to give the customer the illusion they are buying a quality product.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> See our Buyers Guide for much more detail on how to spot good quality vs poor quality.