With growth of solar hot water systems flat in the U.S., companies operating in the space are turning to other related areas of business.

In September, Washington, D.C.-based Skyline Innovations rebranded itself as Nextility, and expanded from solar hot water services into energy brokerage services for small businesses. Nextility CEO Zachary Axelrod insisted that the move "is not a pivot," but the sluggish pace of solar thermal adoption was a major factor in the decision.

Sunnovations, another solar hot water company based just outside D.C., has followed suit. The company has been selling a wireless sensor, called the Ohm, designed to make solar hot water monitoring cheap. The monitoring system was priced at $499 -- half of what other similar devices cost. 

Even at that price, business activity was slower than expected due to the anemic state of the solar thermal market. So Sunnovations has reconfigured its monitoring system and turned it into a remote control system for residential water heaters. The device is called the Aquanta.

"We're still using the same sensing technology. But we have created a different controller," said Matthew Carlson, the CEO of Sunnovations.

Aquanta uses an enthalpy sensor to monitor the energy in a water tank and the energy expended when hot water is being consumed. The information is displayed on a mobile app that displays usage and savings suggestions, hot water availability, maintenance issues and offers a remote turn-off option.

"It's basically a very souped-up version of a water heater timer. We've added analytics and think we've made it very different and compelling," said Carlson.

The intelligent water heater market is similar to solar hot water: small. However, numerous companies are hoping to leverage home water heaters for grid balancing. In Hawaii, for example, the local utility is working with Steffes, Sequentric and Battelle to install networked water heaters at small commercial businesses to enable hourly load shifting and second-by-second regulation.

Carlson wants to break into the residential sector, where a significant amount of the average household's electricity use comes from water heaters. Although remote switches on water heaters have long been used for utility demand response programs, Sunnovations thinks it has an offering that can empower the consumer to realize much deeper savings.

Nest offers a relevant example. Remote switches on air conditioners have been a common tool for utilities in residential demand response programs. But Nest came in with a smart thermostat desired by consumers and built a demand response offering that appears to be performing much better than traditional programs.

Sunnovations still doesn't have any hard data on its device's energy savings. Carlson only pointed to vendor studies that showed controls could cut energy consumption from water heaters by 10 percent to 20 percent.

Sunnovations plans on targeting do-it-yourselfers as its first customers. The company has rolled out a Kickstarter campaign to fund the first batch of Aquanta devices, which retail at $149.