In an article highlighting Dandelion, a ground-source heat pump startup that grew out of Alphabet's moonshot lab (formerly Google X). From the article:
According to a report compiled by Navigant Research for the business association Advanced Energy Economy, revenue from the sales and installation of geothermal heat pumps in the US has grown steadily in the past six years, “rising from $93.6 million in 2011 to $154.3 million in 2016, with an increase of six percent from 2015 ($145.1 million) to 2016.”