Wood is the oldest but even today the most important carrier of solar energy. The actual potential of wood energy depends on waste- or by product quantities, which have no better use in the non energy sector and of energy plantations via short rotation forestry. The economical sensitive potential depends additional on the energy-price-level. The fuel characteristics with low ash and low sulfur content allow the comparison with straw (high ash-c.) coal, oil, and gas. The most important aspect of wood as renewable energy carrier is its nearly closed C-circle. Wood is processed to wood logs (discontinuous charging) and wood chip and/or pellets (automatic charging). Wood log furnaces have to be combined with heatstores (100 l/kW) to avoid emission problems with a heating performance below 50%. Wood chip and pellet furnaces allow similar handling comfort as oil fired boilers. The costs of energy from wood are in the range of 0.06-0.15 DM/kWh. Heating oil leads to total cost of 0.07-0.11 DM/kWh with a oil price of 0.40 DM/l.