Most commercial touchless faucet systems include four electrical loads:

1. Sensor and control board
   This is the “always on” brain. It runs the detection algorithm, timing, safety shutoff, and sometimes self calibration.
2. Emitter and receiver
   Infrared (IR) or time of flight sensing needs an emitter pulse and a receiver stage. These may draw little power on average, but are sensitive to voltage stability.
3. Solenoid valve
   The solenoid is the largest short duration load. Many systems draw a current spike when opening, then settle to a lower hold current. Some designs use latching solenoids to reduce hold power.
4. Indicators and accessories
   LEDs, optional temperature display modules, remote sensors, soap systems, or an external mixing module can add load and increase sensitivity to power sag.

Battery powered touchless faucets are common because they avoid electrical rough in. They are also common in retrofit work where opening walls or adding receptacles is expensive.

Typical battery architectures

• 4x AA alkaline (6V nominal) is a frequent configuration.
• Some systems accept lithium cells, or a dedicated battery pack depending on the brand.
• Higher end designs may incorporate smarter low battery logic and better voltage regulation.

Where batteries shine

• Retrofits and tenant improvements: no need to coordinate an electrician for a single lavatory.
• Distributed failure mode: one dead battery affects one fixture, not an entire restroom bank.
• Fast commissioning: fewer trades involved can shorten close out.

Battery tradeoffs AEC teams should plan around

1) Discharge curve and “brownout” behavior
Battery voltage does not fall linearly. Many alkaline batteries spend a long time near nominal voltage, then decline faster near end of life. If a control board does not regulate voltage well, you may see inconsistent detection or valve chatter before total failure.

2) Current spikes during actuation
Solenoids and LEDs can pull brief peaks. Batteries with higher internal resistance (common near end of life or in cold locations) may sag under load. That sag can cause:

• delayed opening
• shorter run times than intended
• intermittent “dead” behavior that is hard to troubleshoot

3) Maintenance is not optional
Battery powered does not mean maintenance free. It shifts maintenance from the electrical system to the facility team. If you specify battery, you should also specify a maintenance approach.

A battery maintenance plan that works in real buildings

• Replace batteries on a schedule tied to occupancy and duty cycle, not just “when it dies.”
• Standardize battery type across a facility to simplify stocking.
• Require accessible battery compartments for service without removing the entire spout body.
• Include a commissioning checklist item: confirm low battery indicator behavior and reset procedure after replacement.

AC powered touchless faucets typically use a transformer that supplies low voltage DC to the faucet controller. You might see plug in transformer to a receptacle under the sink, hardwired transformer or power supply feeding multiple fixtures, or a dedicated low voltage distribution strategy in large restrooms.

Where AC power wins

1) High traffic restrooms where uptime matters
Airports, stadiums, hospitals, schools, and transit hubs benefit from power stability and reduced routine battery labor.

2) Consistent sensing behavior
Stable voltage improves repeatable detection and reduces weird edge cases. This matters in spaces with variable lighting, reflective finishes, or multiple fixtures close together.

3) Predictable O and M
Facility teams often prefer not to manage batteries across dozens or hundreds of points.

AC power considerations that affect design and installation

1) Electrical coordination and access

• If you specify plug in power, you need a receptacle location and access strategy.
• Service access matters. A hidden receptacle behind a fixed panel is not helpful when a transformer fails.

2) Power supply safety and listing
Most faucet power supplies are low voltage, but the installation still interacts with code and product listing requirements. It is also common to see “Class 2” style low voltage approaches in building systems. Make sure the supply is appropriately rated and installed per local code and manufacturer instructions.

3) Shared power supply risk
If one transformer feeds multiple faucets, one failure can disable multiple fixtures. This is not automatically bad, but it must be intentional. In critical facilities, you may want redundancy or segmented feeds.

4) Noise and interference
Low voltage runs and poor grounding can introduce electrical noise that affects sensing and control logic. This is more likely in long cable runs or crowded ceiling spaces. Keep wiring organized, avoid running low voltage parallel to high voltage in tight bundles, and follow the manufacturer’s cable length limitations.

Hybrid systems typically mean one of these:

1. AC primary with battery backup
   The faucet runs on AC power, but automatically switches to battery mode during outages.
2. Battery primary with optional AC adapter
   The faucet can accept an AC adapter for long term use, but can still run on batteries if AC is removed.
3. Multi fixture AC with local battery backup
   A shared power supply feeds a bank of fixtures, but each fixture can fail over to battery.

Why hybrid is attractive

• Keeps sensing stable during normal operation
• Maintains service during outages (important in healthcare and emergency situations)
• Reduces routine battery replacement burden because batteries are used mainly during interruptions

Hybrid design details that matter

1) Failover behavior

• Does the faucet switch instantly or does it reboot?
• Does it lose calibration settings?
• Does it signal the mode change to the user or staff?

2) Battery health in standby
Batteries sitting idle for long periods can still degrade. In a hybrid system, batteries can be forgotten until they are suddenly needed. Facilities should still schedule battery replacement even if usage is minimal.

3) Commissioning and troubleshooting clarity
Hybrid systems reduce downtime, but can increase confusion. A faucet that “still works” on batteries may mask an AC failure until a later date. Spec teams should require clear indicators or documentation.

Tenant improvement, light commercial, small restroom counts

Battery is often the lowest friction choice if:

• maintenance staff is reliable
• battery access is straightforward
• fixture counts are not huge

Large restroom banks, high traffic public facilities

AC or hybrid is usually better because:

• routine battery replacement becomes a labor cost and a risk
• stable performance reduces nuisance calls
• shared power can be planned cleanly at rough in

Healthcare and critical environments

Hybrid becomes attractive when:

• you want AC stability for everyday performance
• you need continued operation during outages
• you want to avoid the perception of “restroom failures” during emergency power transitions

Even without manufacturer specific data, you can estimate relative battery stress using a duty cycle approach:

• Standby draw (always on control board) runs 24/7
• Event draw happens per activation (sensor detect + solenoid open/close)
• Event count depends on occupancy and behavioral patterns

Practical ways to make this useful in specs:

• Ask for a stated battery life under a defined usage rate (example: “X activations per day”)
• Require that battery replacement can be performed without removing the faucet body
• Include spare battery provisioning in closeout documents for facility staff

These reduce punch list time and prevent “mystery failures”:

• Verify water pressure is within the fixture’s operating range before troubleshooting sensor behavior.
• Confirm the faucet is not being “fooled” by reflective basins, mirror edges, or nearby fixtures.
• Keep power wiring clean, strain relieved, and protected from moisture.
• Document transformer locations and circuit or feed identification for AC powered installs.
• For hybrid systems, test failover at closeout: cut AC, confirm continued operation, restore AC, confirm settings retention.