The Webasto Air Top Evo 40 and Air Top Evo 55 engine-off heater systems offer comfort, safety and heating capacity for various applications on medium duty and commercial vehicles, according to the company. These heaters feature an automatic cold-start system, and they include an automatic altitude adjustment for elevation up to 7,218' above sea level. The Air Top Evo 40 has a maximum heat output of 13,650 BTU/h, and the Air Top Evo 55 has a maximum heat output of 18,800 BTU/h. Both heaters are available in diesel (12/24V) or gasoline (12V) models.