Outpatient facilities have been deployed more frequently than ever over the past 10 years. This rise can be attributed to government payment policies that support providing services in lower-cost settings. Such policies are forcing health care systems to focus on wellness to help align them with the government’s reimbursement cost structure. 

That said, clinical innovation and patient preference is also tilting the balance in favor of outpatient settings for hospital services. These clinical innovations and technological advances are allowing many surgical procedures to be done in outpatient settings. Outpatient facilities provide many of the same services as hospitals but in smaller, more localized ways, allowing patients to receive specialized care in the convenience of their own neighborhoods. 

As the health care sector continues to trend toward these types of construction projects there is some debate over the electrical distribution design needs across different types of outpatient facilities. Each outpatient facility requires careful analysis of its categorization. This is determined by the services provided and level of patient care yielded. This is especially important in facilities with outpatient surgical suites, as the similarities between different types of spaces can lead to gray areas in code interpretation. Ambulatory surgery centers (ASCs) and office-based surgery centers (OBSCs) often have overlapping programs that can lead to confusion in categorization and subsequent design. Many considerations must be taken into account when designing the electrical distribution for both ASCs and OBSCs, and that goes for new and renovation construction and retrofits.



ASCs are modern medical facilities that focus on providing specialized, same-day surgical care. Specialties served include ophthalmology, orthopedics, endoscopy, and more. ASCs typically treat patients who have already seen a health care provider and have chosen an appropriate procedure for their condition(s). ASCs have critical care spaces that generally are higher acuity than OBSCs.

OBSCs, on the other hand, are primarily office settings where surgical procedures are performed. Some level of anesthesia may be required during the procedure, but some procedures may be performed without anesthesia. The most common modalities performed in OBSCs include gastrointestinal, plastic surgery, dental, and pain management. 



ASCs and OBSCs are very similar in programming, so we must first look at the codes categorizing these different surgical spaces as they are key factors in electrical system design. The International Building Code (IBC), NFPA 99 (Health Care Facilities), and NFPA 101 (Life Safety Code) define ASCs and OBSCs in various ways. Many states have also adopted Facility Guidelines Institute (FGI) guidelines as code-mandated design requirements for ACSs and OBSCs — OBSCs typically have less stringent requirements than ASCs.

The IBC Business Group B defines ASCs and OBSCs under “ambulatory care facility,” as they both provide patient care on a less than 24-hour basis to persons who are rendered incapable of self-preservation by the services provided. 

NFPA 99 provides more specific parameters regarding ambulatory health care and defines ambulatory health care as services or treatment to four or more patients who are rendered incapable of self-preservation under emergency conditions without the assistance of others. By definition, ASCs have four or more patients who are rendered incapable of self-preservation in emergency conditions. With the addition of the “four or more” parameter, this is one factor that separates OBSCs from ASCs.

This means OBSCs can range from basic patient care up to critical patient care with no more than three patients rendered incapable of self-preservation in an emergency condition.



Health care organizations establish their own internal standards and rules of operations for their facilities. Accreditations ensure these organizations meet the regulations and standards set by governing bodies. 

The Social Security Act mandates a minimum health and safety standard for health care providers participating in Medicare and Medicaid programs.

The Secretary of the Department of Health and Human Services has designated the Center for Medicare & Medicaid Services (CMS) to administer the compliance and accreditation aspects of these programs. The federal and state governments provide funding to health care providers that participate in Medicare and Medicaid programs as an incentive to meet and exceed the standards set forth by CMS. CMS governs the accreditation for ASCs. CMS may or may not govern OBSCs depending on the program.  

The federal government looks for practical and cost-effective methods to ensure quality health care is provided to patients by health care facilities. One way this is achieved is by recognizing private accrediting organizations, which allows a larger reach for recognition of more health care facilities to meet Medicare and Medicaid patient care quality standards.

The Accreditation Association for Ambulatory Health Care (AAAHC) is a private accrediting organization that encourages and assists ambulatory health care organizations to achieve patient care in efficient and cost-effective ways. The AAAHC has focus and experience surveying and accrediting ASCs. 

The American Association for Accreditation of Ambulatory Surgical Facilities (AAAASF) is one of the largest private, not-for-profit outpatient accrediting organizations. The AAAASF accreditation ensures facilities comply with the standards of professional training, operational safety, and the physical layout of the center. 

The American Osteopathic Association/Health Care Facility Accreditation Program (AOA/HFAP) focuses on providing CMS-deemed accreditation to osteopathic-centered health care facilities. These programs keep cost-effectiveness and education in mind while emphasizing a user-friendly approach.

The joint commission is an independent, not-for-profit organization that accredits a wide range of health care facility modalities from laboratory, nursing care, behavioral health, home health care, and ambulatory and office-based surgery. The joint commission accreditation process focuses on patient rights and education, infection control, and many more characteristics.


Alternate Power Source

The requirement of an alternate power source is dependent on the category of patient care being provided and the facility’s load characteristics. For outpatient health care facilities, the driving requirements are the need to supply power to loads on the essential electrical system within 10 seconds and maintaining this power for the necessitated amount of time without needing to refuel or implementing a new supply of power. The necessitated amount of time is set by the code-mandated minimum for egress and the amount of time required to safely complete any procedure performed in the facility. If the time needed to complete the procedure is undefined, the alternate power source should supply emergency power for the full duration of operating hours to accommodate any same-day surgery case. Typically, the method of meeting these requirements is by generator and/or uninterruptable power supply (UPS). 

NFPA 99 defines the risk category for patientcare spaces. ASCs fall under Category 1 or 2 because of the critical and general patient care programming. NFPA 99 requires Category 1 and Category 2 patient care spaces be served by an alternate source of power. Category 1 patient care areas shall be supported by a Type 1 Essential Electrical System (EES) with life safety, critical, and equipment emergency power branches. Category 2 spaces may be served by a Type 1 or Type 2 EES. Type 2 EESs are only required to have life safety and equipment branches. The types of EESs are as defined in NFPA 110. 

OBSCs can range from Category 1-4, as they have a wide range of low-impact diagnostics to invasive procedures. Category 1 and 2 patient care spaces within OBSCs have the same requirements as stated previously for ASCs. Category 3 and 4 patient care spaces are not required to be supplied by an essential electrical system. Life safety loads still require emergency power whether an EES is provided or not. At a minimum, for both ASCs and OBSCs, NFPA 101 mandates emergency power be provided for 90 minutes for operation of emergency egress lighting, fire alarm, and other life safety loads. As these systems are smaller in load, battery backups are acceptable alternatives to providing an EES. 


Alternate Power Location

The location of the alternate power source must be located on the facility property. Generators can be installed either outside or inside, so long as they are protected from damaging elements that could result in interruptions of the emergency distribution. Generators installed indoors are required to be in a separate two-hour-rated room away from the normal power distribution. Generators installed outdoors shall have a suitable enclosure capable of resisting snow and rain.

Essential power distribution equipment is permitted to be installed within the same room or enclosure as the generator. No other equipment except for the equipment serving the generator is permitted within this space. Considerations of weight; vibration; noise; fuel storage; and heating, cooling, and ventilation shall be considered when designing the generator location. 

Life safety systems utilizing a battery backup may be installed per device or piece of equipment needing backup, such as with a light fixture having an emergency ballast or in a centralized location, such as with an emergency lighting inverter.


Transfer Switches

Transfer switches are required to connect to the alternate source of power when normal power fails; however, the question of how many are needed depends on several factors including level of patient care acuity, reliability, and emergency load.

Whether in ASCs or OBSCs, one transfer switch may be used if the continuous load on the essential electrical system is 150 kVA or less; however, all other essential electrical system requirements and regulations must be adhered to. Also, when installing only one transfer switch to transfer between power sources, failure of the transfer switch means failure of power transmission to the emergency distribution system. Even if the load on the essential electrical system is 150 kVA or less, more than one transfer switch may be installed. 

If the load on the essential electrical system is more than 150 kVA, the number of transfer switches depends on the category of patient care. More than one transfer switch may be installed for each emergency branch.

Each switch shall be in a separate enclosure to negate the failure of one potentially damaging another, such as in a case of an electrical fault. 
Automatic transfer switches (ATSs) are required for Type 1 and Type 2 essential electrical systems. Automatic or manual switches may be installed for all others.


Operating rooms

Operating rooms (ORs) can be located within ASCs and OBSCs. Whether an operating room is located within an ASC or OBSC, the requirements are the same. Operating rooms are critical care spaces with high acuity requirements for invasive procedures. The presence of an OR can elevate the requirements of the entire EES. 

Each OR shall be provided with a minimum of 36 125-V, 15- or 20-amp receptacles per FGI, NFPA, and NEC 517. Twelve of the 36 are required to be located convenient to the operating table on which the patient lays. A minimum of two receptacles are to be placed on each wall.

Operating rooms are considered wet procedure locations unless a risk assessment conducted by the owner or the owner’s life safety consultant deems it otherwise. This can be dependent on a lower acuity level of operation being conducted within the room that is not considered a wet procedure.

Wet procedure locations require special protection against electrical shock due to the invasive nature of procedure. The special protection can be provided via a power distribution system that inherently limits the possible ground-fault current, such as with isolation panels or with ground fault circuit interrupters (GFCI). The intent is to reduce the possibility of electric shock to a patient while his or her body cavity is open and vulnerable. 

Isolation panels are commonly utilized to provide power to emergency circuits within an OR. Special considerations need to be taken in regards to circuit run length, as isolation panels are sensitive to system impedance and need to be kept within the manufacturer’s limitations for proper operating of the isolation monitor. Multiple isolation panels may be considered in order to meet these requirements. 

One or more battery-powered lighting unit should be provided within operating rooms to provide lighting in the interim of loss of power before the EES reestablishes power. This is intended so that the patient bed is illuminated at all times throughout the surgery for patient and physician safety. It’s important to note that these battery backup emergency lights are not intended as life safety lighting. Deliberate switching does not constitute loss of power, and these units shall be installed per NFPA 70 to sense for loss of normal power via an unswitched hot-leg.


Procedure Rooms

Both ASCs and OBSCs may have procedure rooms with similar programs in their suites, though only noninvasive practices may be conducted within these rooms. The level of electrical design is dependent on procedures performed within these rooms for both ASCs and OBSCs. Invasive surgical procedures may not be performed within a procedure room. 

Each procedure room shall be provided with a minimum of 12 receptacles. Eight of the 12 are required to be located conveniently to the patient table for a physician’s use, and one receptacle shall be provided on each wall.



Many outpatient health care facilities are retrofitted into existing structures, including existing malls, commercial tenant buildings, or stand-alone retail. It’s important to understand the potential impact, cost implication, and scope this may have depending on the existing structure. A complete upgrade to the electrical system may be required if it was not previously designed for such new occupancy. 

Whether renovations occur for an ASC or OBSC, the level of impact is dependent upon on how much alteration to the existing building is planned and the difference in the existing electrical distribution versus the type of normal and essential electrical system required for the new space. Challenges often arise as, generally, the existing building’s electrical distribution was not previously designed for the increased load density and electrical distribution components required by ASC and OBSC outpatient facilities.

There are differing levels of alterations as defined by the International Existing Building Code (IEBC).

  • Alteration level 1: Include the removal and replacement or the covering of existing materials, elements, equipment, or fixtures using new materials, elements, equipment, or fixtures that serve the same purpose.
  • Alteration level 2: Include the reconfiguration of space, the addition or elimination of any door or window, the reconfiguration or extension of any system, or the installation of any additional equipment.
  • Alteration level 3: Apply where the work area exceeds 50% of the building area. 

There is more emphasis on level 2 and 3 alterations, as level 1 alterations do not require significant changes to the existing electrical system.

Level 2 and 3 alterations may be done without requiring the existing building/space to comply with the requirements of the new construction. Only the new construction and renovated work areas shall be required to meet the applicable codes in Group B occupancies. Existing wiring in all work areas in Group A-1, A-2, A-5, H, and I occupancies are required to be upgraded to the applicable governing codes and regulations.



The design of outpatient facilities can be challenging, but it’s very important that there is an understanding of the type of programs that will be in the building and the accreditation the facility will be seeking.

ASCs and OBSCs within existing buildings require careful analysis of the existing services. Often, the existing infrastructure was not designed to accommodate the increased needs these programs require. Commercial or residential buildings, for example, generally have lower power density demands than health care programs. As such, distribution may not have the capacity to accommodate a retrofitted ASC or OBSC. Additionally, health care emergency services have higher requirements because of inherent patient care risks. This leads to requiring generators, transfer switches for multiple tiers of power, and added distribution that an existing building may not already have. Cost and space for these added systems and equipment may also be obstacles to consider. The health care facility provider may also look for accreditation that presents further requirements. Accreditation program and standard requirements can drive electrical system design provisions that may pose challenges to meet. Construction of ASCs and OBSCs require thoughtful considerations to electric design.