Heat-up time is based on ambient temperature, so the room will get to temperature faster when the outside air is 50F when compared to, say, 20F. Also, the optimal temperature varies by individual; some people like a lower temperature heat such as 165F, while others prefer a higher temperature of, say, 190F. However, as a rule of thumb, the room will heat to 165F in 30-40 minutes, and to 190F in less than 60 minutes.