The farmer’s monthly electricity bill to the power company using the mains electricity supply was £400.The biogas generator for the farm would cost £20 000 to buy and install.Assuming the biogas generator provides all of the electricity requirements for the farm, what is the pay-back time for the generator?Payback time = _____ months

Initial cost = £1440Saving = £120 each yearCalculate the payback time.Payback time = _____ years

Scott has just spent £6160 on solar cells to go on his roof.In the first year they saved him £560 on his electricity bill.Calculate the total payback time of the solar cells.Payback time = _____ years

If the system costs $88,792, how many years would it take to pay off the investment?  Assume the energy is worth $104 per day.  Assume there are 328 operational days per year (the rest are maintenance days).

Initial cost = £18 000Saving = £3000 each monthCalculate the payback time.Payback time = _____ months54 monthsLess than 1 month15 months6 months

If the system costs $110,103, how many years would it take to pay off the investment?  Assume the energy is worth $83 per day.  Assume there are 314 operational days per year (the rest are maintenance days).