The ILLUMRA Wireless Door/Window Sensor model E9T-MDCCP maximizes the energy savings of heating and air conditioning systems by providing wireless status of windows and/or doors. The sensor uses a magnet contact switch that is powered by a solar cell and communicates with a wide variety of ILLUMRA products. Energy waste can be reduced by 20 to 60 percent by disabling blowers and/or adjusting temperature setpoints in HVAC systems when windows and doors are left open. The wireless Door/Window Sensor is a key component to reducing energy waste in hotel, condominium and dormitory buildings. These sensors communicate with ILLUMRA's E9R-x series of receivers.