The calculation
Fuel input cost/GJ = landed price per tonne ÷ NCV in MJ/kg.
Useful heat cost/GJ = price ÷ (NCV × efficiency as a decimal).
Useful heat cost/MWh = useful heat cost/GJ × 3.6.
Fuel kg/h = useful heat kW × 3.6 ÷ (NCV × efficiency).
Monthly tonnes = kg/h × hours/day × days/month ÷ 1,000.