After an energy audit on her home this summer, Meredith Keelan spent $12,000 to install six solar panels and deep insulation in her attic.

She fitted a solar-powered attic fan and bought a new fuse box. The solar fan means her mechanical ones rarely blow. Ms Keelan uses three times less power during the day, when the solar panels power her home, than at night, when she relies on the grid. Once she pays off these energy improvements, Ms Keelan will invest in six more panels, at $1,700 each (€1,190, £1,045).