What is the break point below which alternative energy is NOT costeffective? While working up an estimate for a customer, I realizedthe proposed system simply could not be justified on a cost basisand probably not on any other basis either. Customer wanted toswitch to a wood burning boiler for hydronic heat. He lives in aforestry mill town in Northern Canada. He has ample free scrap wood. But he wanted to power thecirculation pumps with solar power, not utility power. He is atpresent connected to the grid and plans to continue using utilitypower for other things but wanted to be "a little less dependent onthem". After determining the electrical loads and calculating theamount of solar panels needed, inverter plus batteries to run theinverter during no sun at night and of course during the longwinter at latitude 54 with little sun, I concluded this projectjust did not make economic sense. Cost of the electricity is 8cents per kilowatt and amounts to $2 per day to run the circulationpumps. Cost of equipment came to $7000 approximately if you usedcode legal equipment. Meaning certified and approved equipmentproduct instead of just functional and technical suitableequipment.
For instance he wanted an automatic transfer switch in case thebattery got depleted, in which case he would switch back to utilitypower. The only approved transfer switches cost many hundred ofdollars and are designed to transfer a whole household powersupply. This application only required switching 10 amps at themost. A $15 DPDT Potter and Brumfield relay would suffice. Exceptit would not be certified as approved for that use. In which caseyou would have to pay for a 'special inspection' which cost$200.