The home has a backup oil furnace used to provide heating and hot water when the primary systems cannot. This is not a frequent occurrence unless there is a prolonged cold spell in the winter or a week of rain in the warmer months. I am looking into Bio fuel as soon as they can work out how to produce it without using the general food supply. There have been many innovations lately to use feedstock's that are renewable and do not compete with the food supply. The oil furnace is a marvel of engineering when you think of the amount of energy that can be produced in a short period of time. It also requires very little attention to run it. The downside is it needs oil that is imported, not renewable, and produces positive CO2 emissions. The oil furnace is connected in parallel with the wood gasification boiler and will run automatically when the wood boiler and its hydronic storage tanks run out of energy. We have added a Hot Water Heating System Fuel Economizer to the oil furnace that allows a minimum of 10 % additional efficiency to be achieved. This is accomplished by the controller monitoring the oil furnace as it runs and determines if there is additional latent heat in the oil furnace. This utilizes additional energy by entering into a economizer mode, keeping the oil furnace from turning on until all the latent heat is utilized. In the parallel configuration with the wood boiler, we currently see over 50 % utilization because of the additional latent heat from the the wood boiler, its two hydronic storage tanks and the insulated piping between the systems. Bottom line is we are using half the energy when the oil furnace is running as a backup system to the wood boiler during the winter months. The home has 5 zones and a indirect hot water heater connected to the furnace. The home also has programmable thermostats in each zone.