Case Study - General Hydroponics


Located in Santa Rosa, California, General Hydroponics, Inc. (GH) manufactures indoor agricultural systems and nutrients for flower and vegetable growers worldwide. With clientele spanning research universities, national laboratories and high-tech gardeners, GH is innovating how nature and technology work together to enhance flavor, maximize yield and produce top-quality crops.

The company’s Sonoma County facilities comprise 223,000 square feet of modern industrial space used for product development and production. Eight years earlier GH installed a 101 kW photovoltaic (PV) system to reduce electric bills and showcase the company’s strong environmental commitment.


A large portion of the company’s utility bill is natural gas consumption, used in manufacturing various nutrient solutions. GH considered a handful of traditional solar thermal systems, but the forecasted payback period was too long to justify the required capital investment.


With Cogenra’s solar cogeneration solution, GH was able to further reduce their spending on energy. Cogenra’s solar cogeneration increases GH’s solar electricity capacity, while reducing an estimated 60% of their current natural gas usage via solar hot water.

Cogenra collaborated with Berkeley-based Sun Light & Power to assess the installation site and GH’s energy needs. Together, the two companies designed and installed a 75 kWth+e solar cogen system mounted on a standard solar racking system on the GH rooftop. Comprising 36 Cogenra PVT (photovoltaic-thermal) receivers, the system produces 15 kW of electricity and roughly 60 kW of thermal energy.

Thanks to Cogenra’s modular, plug-n-play design, the rooftop installation period lasted a mere three weeks from construction start. The array is configured in 6 rows of 6 SunDeck® PVT modules, occupying approximately 2,800 square feet of roof space. The lightweight architecture of the Cogenra array required no special permitting or roof modifications to support the additional load, which is crucial to keeping costs and construction times to a minimum. The system is complete with fully integrated hydronics, controls and inverter installation, granting GH access to remote monitoring and performance diagnostics 24/7.

Heated up to 70˚C, the hot water generated from the Cogenra system is applied to GH’s General Organics manufacturing process to heat water used in producing the complex nutrient blends shipped to flower and vegetable growers worldwide.


GH’s solar cogen array is expected to offset more than 3,500 therms of natural gas use, annually. The dual solar hot water and electricity generation qualifies the installation for both solar thermal and solar electric rebates and tax incentives offered at the state and federal level, significantly shortening the payback period. Under the California Solar Initiative (CSI), GH is eligible for the solar hot water rebate offered at the first-tier level of $12.82 per therm of year one displaced gas and the CSI photovoltaic incentives.

With the CSI and federal rebates, GH will experience a return on their investment in less than five years, while immediately hedging against future utility price hikes and gas price volatility.

GH values environmentalism with a strong corporate commitment to sustainability. Cogenra’s solar cogeneration system is a core element of their ongoing efforts to ‘green’ their daily operations. The hybrid solution offers a clean alternative to grid-fed electricity and limits the amount of natural gas burned on-site, improving local air quality. The installation will reduce greenhouse gas emissions by 37 metric tons per year, the equivalent of offsetting 4,200 gallons of gasoline burned annually—carbon savings equal to 1,000 trees over 10 years of sequestration.