Location: Fitchburg, Massachusetts

Watts: 2,880

Monthly Production: 286 kWh

Date: September 2017

This solar energy system is small by 2017 standards, with only eight panels. But the SunPower panels pack a punch. And the impact on the family’s electric bills is kind of mind-blowing. Today, they pay Unitil about 23₵ per kWh. With normal inflation, that will be more like 63₵ in 25 years time. But with solar? Their average price per kWh is just 12₵, locked in for 25 years.

The roof, by the way, is metal shingles.