The targets for energy saving in Dutch horticulture are high. Research follows the two lines: total energy reduction and sustainability. The principles for that are: maximum use of natural sunlight (free energy input to greenhouse, free light for crop growth and production); maximum insulation (prevent energy losses through greenhouse covering); efficient use of energy (e.g. next generation cultivation strategies, mechanical dehumidification, diffuse light, optimum CO2, low temperature heating, high humidity levels); replace fossil fuels by renewable energy sources (e.g. geothermal, biofuels, solar energy, wind). Research results are shown in the Innovation and Demo Centre for Energy in Bleiswijk (IDC Energy). The goal of this paper is to describe some of the newest results of the Dutch research programme on energy saving focussing on energy conservation by greenhouse system design and the use of sensors and decision support systems. Energy savings on heating of 50-70% have been realised for a tomato crop compared to average practice in a highly insulated greenhouse. Another greenhouse concept focusses on the maximum use of natural sunlight during low solar elevation. With 3D ray-tracing models the effect of greenhouse roof angle, orientation, shape and construction materials as well as the effect of different diffuse coverings with anti-reflective coatings and hydrophilic condensation properties on light transmission during winter months has been quantified. It is expected to gain 10-20% more natural light by the new greenhouse concept during winter months. Wireless sensors are used to measure temperature and humidity distribution at many spots inside a greenhouse. Innovative web-based decision support models have been introduced into practice to give insight in the climate distribution and to predict the risk for crop health. For that a new climate control strategy the "Roaming Climate Measuring Box" and a "Botrytis Alert" have been developed. The greenhouse climate is automatically controlled on basis of the most humid or coldest spot in the greenhouse. That way up to 10% of energy can be saved and the risk for botrytis can be minimised. Two new sensors measuring actual crop photosynthesis have been developed and are currently tested in practice. Sensors are based on (i) the CO2 balance of the greenhouse and (ii) measuring chlorophyll fluorescence of a crop by means of laser and camera technology. In the future, such information is envisaged to be directly used for greenhouse climate control or crop management.