Two of the Bay Area's top clean energy companies -- Nest and Sunrun -- have joined forces in a marketing campaign to pair smart thermostats with solar.

Under the partnership, Sunrun customers can get a $250 Nest thermostat for free, along with another $250 credit for electricity; Nest customers interested in solar can get a $500 voucher for a Sunrun solar system. 

Nest is the Palo Alto-based company founded by two former Apple engineers who wanted to create a smart thermostat with the same brand recognition and consumer-focused experience as an iPod or iPhone. Sunrun is the San Francisco-based solar company that helped pioneer solar leases and power purchase agreements. 

The two companies are hoping they can leverage the "cool" factor of each other's brands and entice more customers to buy products.

The partnership comes as more solar service companies build offerings with companies outside the solar industry to reach new customers. Sunrun, SolarCity, Sungevity and Clean Power Finance have all established relationships with leading retailers like Home Depot and Lowe's.

One Block Off the Grid is also working with to provide solar systems as part of a broader residential energy management platform.

And after reportedly struggling to get its own efficiency service off the ground, SolarCity has formed a new service to connect existing customers with energy efficiency contractors. 

Nest is also beefing up its partnerships with utilities in order to provide more residential demand response programs, which it calls "Rush Hour Rewards." The company is working with Austin Energy, Green Mountain Energy, NRG Energy and Southern California Edison. Nest continues to use demand response as a way to leverage new sales of its thermostat, while enhancing customer engagement. 

“With increased interest in finding ways to conserve energy, the Nest-Sunrun offering comes at the perfect time,” said Erik Charlton, Nest vice president of business, in a statement on the Sunrun website.

With roughly 40,000 smart thermostats being shipped each month, Nest has made big strides by selling its product through large brick-and-mortar retailers and online stores like Amazon. Could targeting solar customers through companies like Sunrun provide even more of a boost?