Trends are positive for solar electric power. Panel prices have been dropping for years, while panel output and efficiency has been rising. Mini-split heat pumps are also riding a wave: Every year, one of the big name-brand manufacturers leap-frogs the others, posting another jump in efficiency.

For ReVision Energy in Portland, Maine, those two positive trends are the key to a new business model. For several years, the company has been selling Mainers on the idea that the smart way to heat your house is to put solar panels on your roof, and mount a mini-split heat pump on your wall. Some houses only get panels, and some houses only get mini-splits; but as ReVision founder Fortunat Mueller said in February during a three-hour technical presentation at the Building Energy 14 conference in Boston, “To me, the easiest path to net zero—if there are easy paths to net zero—is an on-site, grid-tied solar electric system and some form of electric heat, either resistive or a heat pump. Heat pumps let you cool and heat efficiently with electricity, and electricity is easy to make off the roof.” The combination is enough to serve as a stand-alone heating system, if the house is well suited for the strategy.

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