Sonoma Valley Hospital

About This Project

Powering Critical Care with Resilient On-Site Energy

Sonoma Valley Hospital | Sonoma, California

Project Overview

In Northern California, wildfires, earthquakes, and Public Safety Power Shutoffs can create serious challenges for healthcare facilities that need reliable power around the clock. For Sonoma Valley Hospital, maintaining continuous operations during grid disruptions is not just an operational priority. It is essential to patient care and community safety.

To strengthen energy resilience, Sonoma Valley Hospital partnered with Unison Energy to implement an on-site combined heat and power microgrid powered by a natural gas 2G aura 412, 420 kW CHP system. The system supports daily hospital operations by generating on-site electricity and capturing usable thermal energy for the hospital’s hot water and boiler systems.

With 2G CHP technology at the center of the microgrid, Sonoma Valley Hospital gains a more resilient, efficient, and cost-predictable energy solution designed for the realities of operating critical infrastructure in a wildfire-prone region.

The Challenge

Hospitals cannot afford power interruptions. In Sonoma Valley, the risk of grid outages has increased due to wildfire-related Public Safety Power Shutoffs, severe weather, and natural disasters. During these events, healthcare facilities must continue supporting emergency services, patient care, medical equipment, heating, hot water, and other critical building systems.

Before the project, Sonoma Valley Hospital faced limitations with its existing backup power infrastructure. Grid outages placed added pressure on hospital staff and created the potential for service interruptions, operational strain, and emergency planning challenges.

The hospital needed a solution that could:

• Support continuous operations during planned and unplanned outages
• Provide reliable on-site electricity and thermal energy
• Improve energy efficiency
• Reduce exposure to utility disruptions and cost volatility
• Meet strict California seismic and air quality requirements
• Be implemented without major disruption to daily hospital operations

The Solution

Unison Energy developed a CHP-based microgrid for Sonoma Valley Hospital under an Energy-as-a-Service model. This structure allowed the hospital to implement advanced on-site energy infrastructure without upfront capital investment, while Unison continues to own, operate, and maintain the system over its life.

At the heart of the system is a natural gas 2G aura 412 CHP unit rated at 420 kW. The CHP system is designed to operate in parallel with the utility grid during normal conditions and provide island-mode capability when the grid is unavailable. During an outage, the microgrid can disconnect from PG&E and continue producing power, adding a critical layer of resilience for hospital operations.

In addition to generating electricity, the 2G aura 412 captures thermal energy from the power generation process and uses it to support the hospital’s hot-water and boiler systems. This allows Sonoma Valley Hospital to make better use of the fuel it consumes, improving total system efficiency while reducing reliance on conventional boiler operation.

Key Project Results

• Features a 2G natural gas aura 412 CHP system rated at 420 kW
• Supplies more than 90% of the hospital’s annual electricity needs
• Produces more than 70% of the hospital’s hot water demand
• Achieves 60.5% total system efficiency based on higher heating value
• Provides island-mode capability during grid outages
• Supports critical healthcare operations during wildfires, Public Safety Power Shutoffs, and other disruptions
• Meets California Department of Health Care Access and Information seismic standards
• Meets Bay Area Air Quality Management District air permit requirements
• Delivered through an Energy-as-a-Service model with no upfront capital investment for the hospital
• Designed for future fuel flexibility, including renewable natural gas and hydrogen, as those options become more viable

Why CHP Matters for Healthcare

Combined heat and power is especially valuable for hospitals because healthcare facilities have a constant need for both electricity and thermal energy. Instead of relying only on grid electricity and separate boilers, CHP allows a facility to generate power on-site and recover useful heat from the same process.

For Sonoma Valley Hospital, the 2G aura 412 does more than provide backup power. It supports day-to-day operations, improves energy efficiency, and strengthens the hospital’s ability to remain open and ready when the surrounding grid is under stress.

In critical environments, resilience cannot be treated as a secondary benefit. Reliable on-site power helps protect patient care, reduce operational uncertainty, and give facility teams more control over their energy future.

Built for a Complex Hospital Environment

The project required a highly customized design due to the hospital’s space constraints and regulatory environment. Supporting equipment was strategically integrated into the existing hospital campus, including rooftop placement, while meeting California’s stringent seismic requirements for healthcare facilities.

The system also had to comply with Bay Area Air Quality Management District permitting standards, which are among the most rigorous in the country. These requirements made technical performance, emissions compliance, and long-term reliability essential parts of the project design.

Despite these challenges, the project was delivered without disrupting normal hospital operations, allowing Sonoma Valley Hospital to continue serving its community throughout implementation.

Long-Term Resilience and Future Flexibility

Sonoma Valley Hospital’s CHP microgrid was built not only for today’s energy needs, but also for the future. The 2G aura 412 provides efficient natural gas operation today, while the broader CHP platform supports a practical path toward lower-carbon fuel strategies as renewable natural gas and hydrogen become more accessible and economically viable.

This future-ready approach enables the hospital to strengthen resilience, improve efficiency, and support lower-carbon operations without compromising reliability.

The 2G Perspective

Projects like Sonoma Valley Hospital demonstrate the important role CHP can play in modern healthcare energy strategy. Hospitals need power systems that are efficient, resilient, and capable of operating when the grid cannot.

The 2G aura 412 provides dependable on-site generation, useful heat recovery, and high-efficiency performance in a compact CHP platform. For healthcare facilities, this type of system can support both everyday energy needs and emergency preparedness, helping critical facilities maintain operations when reliability matters most.

For Sonoma Valley Hospital, the result is more than an energy upgrade. It is an investment in operational continuity, patient care, and community resilience.

Closing Statement

When the grid is unstable, hospitals still need to operate. Sonoma Valley Hospital’s CHP-based microgrid shows how on-site energy can help healthcare facilities remain powered, efficient, and prepared during the moments that matter most.

With 2G’s natural gas aura 412 CHP technology at the center of the system, the hospital is better equipped to support its patients, staff, and surrounding community through wildfires, outages, and future energy challenges.