Hi Roger, usually the technical sheets report two values for the runtime: the first value indicates the runtime at minimum power and the second one at max. The boiler will never runs the whole day at min or at max, but it will automatically adjust the power according to the heat demand. The calculation of the average daily pellet usage it is not simple, because it depends on many issues (volume to be heated, insulation of the house, daily routine...). You can ask to a retailer to make an estimation for you, based on your specific case.