Conservatory Cooling: you will need 300 watts / 1071 btu of cooling capacity (note this is not the energy consumption of the system) per square meter of space if your conservatory is south or west facing / is in direct sunlight from 11am - 4pm. If this is not the case then you will need 200 watts / 600 btu of cooling capacity per square meter of space. Conservatory Heating: you will need 150 watts / 535 btu per square meter of space.