Solar heaters are gaining popularity and with good reason- they provide FREE heat. This design uses solar fans to move the heat into the room so its totally off grid and will work during a power outage. Because it is attached to the window it can also be closed by shutting the window and keep the heat inside the unit for off grid solar cooking. This design also allows the unit to be attached all year for ease of use and can keep the heat from entering the home when its not needed. Solar cook all summer, FREE heat all winter; Save money all year!