Why a 24/7 load profile favors solar
An acute care hospital never sleeps. Air handling with high outdoor air requirements, imaging, sterilization, data centers, kitchens, and lighting in patient areas keep a high base load at all hours and all days. Healthcare buildings are among the most energy-intensive commercial building types in EIA's Commercial Buildings Energy Consumption Survey.
For solar that means two things. First, there is essentially no export risk: even a large array rarely exceeds the hospital's midday load, so output is valued at the full retail rate regardless of net metering rules. Second, solar will offset a modest percentage of annual consumption at a campus hospital, because the load is large and roof space is limited by mechanical equipment, helipads, and building height. We report results in dollars and IRR, not percent offset, so boards and finance committees see the real number.
Medical office buildings are different. They behave like office buildings, with weekday daytime loads, tenant physician practices, and often individual meters. The landlord and tenant structuring questions on our office building solar page apply directly.
NFPA 99, NFPA 110, and where solar fits
Hospital essential electrical systems (EES) are governed by NFPA 99, the Health Care Facilities Code, which CMS enforces for Medicare and Medicaid participating facilities, and by NFPA 70 Article 517. In a Category 1 space, the EES is divided into the life safety branch, the critical branch, and the equipment branch. The emergency power supply system is designed, installed, and tested under NFPA 110. For hospitals that means a Level 1 system, and the life safety and critical branches must be restored within 10 seconds (Type 10). Diesel generators remain the standard way to meet that, with required fuel on site and monthly and annual load testing.
The key point for administrators. A grid-tied solar array shuts down when the grid fails, as required by IEEE 1547 anti-islanding rules. Even a battery-backed microgrid is not automatically a code-compliant EES source; any alternate source must meet NFPA 99 and NFPA 110 and satisfy your authority having jurisdiction and accreditor. We design solar and storage as a separate, non-EES system that reduces cost every day and supports resilience, and we coordinate with your existing generators and transfer switches rather than touching the life safety design.
What solar and storage can do for resilience
- Carry non-EES loads during an outage. Generators are sized for essential loads. A battery with islanding capability can support selected normal-power loads, such as additional HVAC, IT, or administrative areas, that the generator plant does not cover.
- Extend fuel. In a long event, solar recharging a battery that carries part of the load can reduce generator fuel burn, which matters when fuel resupply is uncertain after a hurricane or ice storm.
- Support clinics without generators. Outpatient clinics, dialysis centers, and pharmacies that are not required to have a Level 1 system can use solar plus storage to protect refrigeration of vaccines and medications and keep IT running.