Download the embedded energy and payback period spreadsheet.

In this simple assessment, we didn't consider the embodied energy in the inverter, cables and racking required to complete the installation.  Let's assume that the inverter, racks and cables require an additional (per panel):

• 5kg of copper (90MJ/kg)
• 10kg of steel (20MJ/kg)
• 2kg of plastics (70MJ/kg)

i) What is the total embodied energy per panel now? (3 marks)

ii) What is the new payback period (in months)? (1 marks)

Now increase the efficiency of the panels to be 23%

iii) What is the updated payback period (in months)? (3 marks)

iv) In each case, are the rooftop panels still a good idea? (3 marks)