It is given that the upgrades require $16,560 to make the home energy efficient.
It is also given that the upgrades will save $80 per month in energy bills.
Hence the number of months for payback is given by:
![M=(16560)/(80)=207](https://img.qammunity.org/2023/formulas/mathematics/college/5qgrj7bocrjnfa9m6dvv1farm7jip66syt.png)
Hence the cost will pay itself in 207 months.
The time in years and months is given by:
![(207)/(12)=17\text{ }(3)/(12)](https://img.qammunity.org/2023/formulas/mathematics/college/ut6txef4p6isxqyn7rawzzdu1iq48msqf8.png)
Hence the cost will pay itself in 17 years and 3 months.