Sublime baseboard heaters feature a "draft-barrier type upflow air outlet" which is perfect for installing under a window. The advantage of this type of air outlet is that a film or shield is created between the cold glass of the window and the indoor air.
The baseboard heater is just under 3" deep and rises about 7" high. Length varies depending on the unit you choose.
The White Sublime baseboard heater is 24-5/8" and offers a standard watt density of 300 / 225 watts. Ouellet highly recommends the use of an electronic wall thermostat for greater comfort.