Designed specifically to meet the 2018 Lot 20 EU Regulations for enhanced Energy Efficiency, this Prem-I-Air Panel Heater is fitted with a 7-day hour by hour programmable timer and selectable energy saving open window function. The 7 day - hour by hour timer allows you to set the timing of your heater by not only the hours it operates but also the days. For example, if you arrive home from work at 6pm Monday to Friday you can set the heater to come on at 5.45pm on those days only, you may want it to come on earlier on a Saturday and Sunday as you are at home for more of the day, tailor your heating needs to your busy life.