If you half the number of fluoro tubes in your office the amount of heat generated by the tubes will halve. On hot days this will mean a slightly reduced load on your air conditioning system. On colder days, when the building is being heated, slightly more energy will be required to heat the building. In most cases the net impact over 12 months on heating and cooling is negligible. In warmer climates there will be a net saving (eg Brisbane), and in cooler climates (eg Hobart) a net increase in heating energy use. Because heating is usually provided by gas or a heat pump, in very cold climates the cost and greenhouse gas saved by delamping is still much greater than that used to provide the additional heating not provided by the lamps.