Depends on where you live. In states like Connecticut, or certain areas of California (PG&E Bay Area customers), the ROI is very long or simply doesn't pencil out at all. I think for Connecticut, which has high electricity prices but low gas prices, it's just net negative. For me in SF, despite high gas prices the ROI is just too long (5-10 years?), and that's before factoring in the ~$5000+ required for updating my electrical box, which is a conservative estimate because now the city requires the meter to be outside the house, whereas it's currently in the garage.