An infrared sauna heater is not a heater in the sense a traditional sauna means. There is no stove and no stones: there are panels lining the cabin that radiate directly onto you. That changes what you should look at on a specification sheet, and wattage, the number most listings lead with, is the least useful of them.
Carbon and ceramic
Ceramic emitters run hot over a small area, so they heat quickly and produce a noticeable hot spot close to the panel. Carbon panels run cooler across a much larger surface, giving even, gentle warmth that suits longer sessions but takes longer to arrive. Some cabins mix them. Neither is better in the abstract; they feel different.
Panel area and placement beat wattage
Two cabins can draw identical power and feel completely different depending on how much wall is panelled and where. Panels behind the bench only will warm your back and leave your front cool. Look for front, side and calf or floor coverage, and read the panel area rather than the total watts, which tells you about the electricity bill and little else.
Replacement and warranty
Panels are the part that fails, and they are replaceable in a good cabin and not in a cheap one. Check whether the warranty covers the emitters separately from the shell, whether panels are available as spares, and whether swapping one is a screwdriver job or a return to the factory. That answer tells you what the maker expects.
Full spectrum and near infrared
A standard cabin is far infrared. Full spectrum adds near and mid emitters, usually as one extra lamp, and is sold at a premium. If you specifically want near infrared, buy it knowingly. Otherwise a well panelled far infrared cabin at the same price is the better purchase, because panel coverage does more for the session than spectrum does.
Questions people ask about infrared sauna heater
Is a higher wattage infrared cabin better?
Not on its own. Panel area and placement decide how the session feels. Wattage mostly tells you what it costs to run.
Carbon or ceramic emitters?
Ceramic is fast and intense in a small area, carbon is gentle and even over a larger one. Choose on the feel you prefer rather than on a specification.
Can infrared panels be replaced?
In a well made cabin yes, and the maker will sell spares. In a cheap one often not, which is worth knowing before the warranty ends.