Original sentence: All the electricity they produce is measured by one metre and all they use by the other meter.However, the German government charges the customer income tax at their marginal rate for the revenue from power they produce and VAT at 19% for all the power they buy.Instead, depending on their marginal tax rate, they clear about 90 euro to go toward the capital cost of their system.Note that in Germany, customers with their own generation system are double metered.Power costs about 15c per kWh and they recieve about 45c per kWh for power they procuce so you would initially calculate that they would clear 300euro per 1000kWh they produce and use (assume for the example they are equal).When the 20 year grace period ends, a German customer will have to be producing as much as 4 times the power that he uses if he is in the top tax bracket in order to have a zero power bill.With the present system of giving the customer approximately three times the rate for power they produce than for power they use, this is a very seductive system