Definitely Doug 9/3/21: Not Your Father’s Power Socket

by Doug Rice

In the hotel industry, technologists usually leave basic infrastructure elements, like electricity, water, and ventilation, to the engineers. But digital convergence has brought this into question in recent years. While technology and engineering may be separate departments in the hotel, no longer are they independent. Technologists and engineers alike need to expand their horizons.

For many years now, a disconnect has been developing in how buildings distribute power. Hotels engineers may not already see this, but technologists can.

When I was young, virtually everything that needed wired electricity ran on alternating current (AC) power, so it made sense that building power backbones were built around AC. Today, that is no longer the case. Most electronic devices use direct current (DC); unless they run on batteries, that power must be transformed from AC. LED lighting, now the norm, also uses DC power. Because most buildings have AC power, LED drivers were provided with LED lights to convert higher-voltage AC to lower-voltage DC. The driver was either a separate device upstream of the light, or it was incorporated into the LED bulb for compatibility with conventional light sockets.

The AC-to-DC transformation, now performed for most powered devices in hotels, wastes 9% to 15% of the power. It also creates heat, and potentially the need for additional air conditioning to remove it.

DC power options have expanded dramatically in recent years. Power over Ethernet (PoE) technology, which carries power over an Ethernet cable, has been around for nearly 20 years, but during that time the maximum output has grown from an initial 17 watts to 90 watts today, enough to power most LED lights as well as most devices used in hotel guest rooms. Similarly, USB power started out with only 5 watts of DC power but was recently approved to provide up to 220 watts for laptops, phones, and monitors. Battery technology has improved and scaled dramatically, making it practical to store large amounts of power for load balancing or emergency backup purposes. And in just the past few years we have seen the emergence of digital power, which can overcome many of the limitations of PoE.

Most hotels today are built with AC-only power backbones, but the reasons are now mostly obsolete. As a result, we are now seeing the first hotels built with hybrid power, using AC where necessary but DC elsewhere. It is still the early days for DC power backbones, but there are many good reasons for them: construction cost, operating cost, energy cost, sustainability, safety, and the ability to inexpensively control each device centrally to achieve an intelligent building. The experts think it will soon (maybe in one to two years) be feasible to build hotels with entirely DC power distribution. The technical barriers appear to be well understood and solvable with current technologies.

Indeed, California just this week announced plans to update its building code effective in January, 2023 to require new homes and commercial buildings, including hotels, to include solar panels and batteries – meaning DC power.

This week’s topic explores the changes in power technology and the implications for hotels. The technology can be very complex, and at the risk of offending the electrical engineers with some oversimplifications, I will try to keep it basic enough for everyone else to understand. Even a little knowledge may convince you, as it did me, that we are now powering most hotels the wrong way, or at the very least that you should consider other options before building or renovating your next hotel.

Just in case you think this is fantasy, the technologies I will cover here have been fully deployed in commercial buildings, including hotels. To be sure, some of them are quite new, but they work, and the reviews are positive. You can see various of these solutions at The Sinclair Hotel in Fort Worth, at the Alila Marea Beach Resort in Encinitas, and at the Circa Resort & Casino in Las Vegas, to name a few.

The contents of this article were informed by independent research as well as interviews with executives at Sinclair Digital (a low voltage design, installation, and support affiliate of the Sinclair Hotel’s developer), Paladin Technologies (a systems integrator that deployed the technology at the Alila Marea), Igor (a manufacturer of Power over Ethernet devices, including those used at The Sinclair and Alila Marea), and VoltServer (a manufacturer of devices that support its patented Digital Electricity™ technology, deployed at both the Sinclair and Circa Resort). While hotel deployments are still quite limited, each of these companies also has experience in a range of other commercial buildings. My thanks to each of them for supporting this article.

So What’s Wrong with AC Power?

AC power has some advantages that made it the infrastructure of choice for nearly a century. It can run over long distances without appreciable energy leakage, and it can power high-wattage devices like hair dryers, electric heaters, and microwaves on demand. It made sense in the 1950s when most appliances used AC power, and even much later when light bulbs were still mostly incandescent. But the number of cases where AC power works better are shrinking, just as technology is reducing many of the limitations on DC power.

AC power has significant disadvantages. It is expensive to deploy and operate within a building, because it must be run on heavy gauge copper wire, which in turn must be enclosed in conduit or metal-clad cable and installed by a licensed electrician. It must be converted to DC to power most modern devices and lights, meaning energy loss, heat generation, additional cooling to remove unwanted heat, and power converters upstream of, or embedded in, every device. Standard AC voltages sent across a frayed cord can kill hotel staff or guests; they even occasionally lead to the demise of trained electricians doing routine tasks.

Energy loss can be a big issue. Since most lights, electronic, and other devices require DC power, starting with AC means you need to convert it, which results in a 9% to 15% loss of energy. This gets worse with an Uninterruptible Power Supply (UPS), where incoming AC power is first converted to DC for storage, then converted back to AC for distribution, then converted again to DC to power most devices: three conversions, three sources of leakage. In this scenario, it’s easy to waste 30% or more of the power. You can avoid much of this waste with a DC power backbone, and all of it if you add renewable energy sources. Even if you start with renewable sources, which generate DC power that can be directly stored in batteries, you waste energy if you must convert it to AC to distribute it, and then back to DC for the lights and devices.

AC power may need multiple levels of backup. The first level is usually a UPS, which typically receives AC power, converts it to DC, stores it in a battery, and converts it back to AC when needed to power life-safety devices and other critical equipment. A UPS is typically sized to cover short outages and ensure that emergency lights, elevators, and stairway pressurization systems can work long enough to evacuate the building in an emergency. For hotels that want longer protection from power outages, the second level is typically a backup diesel or natural gas generator. These are expensive, bulky, noisy, consume fuel, generate noxious fumes that require ventilation, and must be tested regularly and maintained.

AC power makes it more expensive to keep life-safety devices working in a power outage. The typical electrical closet (known to many of us as an Intermediate Distribution Frame or IDF room) needs AC power and a small UPS for this purpose to keep critical communications (Wi-Fi or distributed antenna system for mobile phones) running; because the UPS generates heat, and heat can significantly battery life, it often needs additional ventilation as well.

AC power also increases the cost of smart buildings, where sensors, thermostats, door locks, lights, switches, outlets, and other devices are networked and can be monitored and controlled from a central brain to improve comfort and flexibility and to reduce energy consumption. To get each AC-powered device connected to the network requires either running a separate Ethernet cable or embedding a wireless radio into each device. Either option significantly increases the cost of the system in comparison with DC PoE solutions that bring both network and power in on a single cable.

Because of this, AC power itself is difficult to manage intelligently. Circuits are designed to provide as much wattage as needed on demand. Any attempt to manage or load-balance a building’s internal power demands will require networking each potential point of power usage.

And DC Power Is Better?

Advances in PoE technology and the arrival of digital power have made DC power backbones much more useful, addressing many of the disadvantages of AC power. It should be noted that while PoE can theoretically support either AC or DC, AC was never standardized or commercialized because it interfered with the data signals running on the same cable. PoE today is therefore a DC-only technology.

PoE is now the best choice for powering most lights, electronic devices, and small motors. Using the same copper as data in standard Ethernet cables, it can provide up to 91 watts per device without any additional electrical wiring. The Ethernet cable does not require conduit in most jurisdictions, nor does it require a licensed electrician to install. PoE does have a distance limitation of about 300 feet, although it is possible to inject power at intermediate points or to use slightly thicker wire to extend the effective range. However, particularly in a sprawling resort setting, it may be challenging to find a power source close enough to remote security cameras or access control devices, which may be located at some distance from any building.

Not all LED lights can support PoE, but more and more manufacturers are adding ones that do to their product lines. This is not difficult: it basically means removing the LED driver that accompanies or is embedded within the device, meaning reduced manufacturing cost. The purpose of the driver is simply to convert AC power to DC to power the light, but with PoE this conversion is done at a PoE node that provides both data and power to multiple devices (typically about one node per guest room). Igor, which manufactures a PoE node that has been used in several hotels, told me that some lighting manufacturers were initially resistant, but had no real issue removing the LED drivers from their products once a commercial opportunity demanded it, and those that did now carry driverless LED lighting as standard products.

PoE has its limits, however. It cannot support larger appliances found in hotel rooms, such as hair dryers, microwave ovens or vacuum cleaners. And even though most consumer devices now plugged into wall outlets require converters and low DC voltage (think phone chargers, laptop power packs, and the like), PoE is not practical for AC wall outlets because of both the wattage limitation and the fact that it is DC.

The latest DC power technology, capable of filling the gap where PoE is impractical or where network connectivity is not required, is digital power. VoltServer offers a patented solution called Digital Electricity™ that has many of the advantages of PoE but fewer of its limitations. Like PoE, it uses low-voltage cabling that does not require conduit or electrical contractors. But in contrast, it supports much longer distances (up to about 2km), both AC and DC loads, and higher wattages (1400 watts AC or 2000 watts DC).

VoltServer’s solution uses what it calls packet energy transfer to send large amounts of electrical energy across structured, low-voltage cable. Just as TCP/IP packetizes data, VoltServer packetizes energy. A transmitter places a short pulse of energy (about 1 joule) onto the circuit, then turns it off to perform a safety check. The safety check can detect a fault, an offline device, a short circuit, or other problem. If the safety check passes, then the process is repeated – several hundred times per second. The total amount of electrical energy that can be transferred is significant, but the amount that can escape is limited to the 1 joule in a single packet, too little to harm anyone or to damage property. The technology is UL-approved and usable in Class 2 applications, essentially the same as low-voltage wiring for thermostats or occupancy detectors.

Unlike PoE, a VoltServer circuit cannot carry high-speed data today, but it can carry power to PoE nodes, where it can be both combined with Ethernet and distributed to lights and guest room devices. It can also deliver either AC or DC power directly to many higher-wattage devices. It runs on standard low-voltage (18/2) wires, requires no conduit, and can be installed by anyone.

Both PoE and packet energy transfer can support flexible modifications to power distribution. If a hotel reconfigures guest rooms and needs a new bedside lamp, low-voltage cable can be run under a carpet or fished through a wall; there is no need to tear out the wall to add new conduit. And while I am not aware that it has yet been used in hotel function rooms, it would be straightforward to assemble a set of components that could be flexibly combined to provide power on demand for a meeting (AC, DC/USB, or both), without needing the traditional heavy extension cords held to the carpet with gaffer’s tape. Given the inflexible electrical infrastructure that is common to large hotel ballrooms with airwalls, this could be a major benefit.

DC power can also be stored in batteries, and together with improvements in battery capacity this also changes the equation for UPS, emergency, and other backup power. The Sinclair Hotel uses a lithium-ion battery bank that was modified by LG to achieve the UL924 certification required for emergency egress, and with enough capacity they eliminated the need for a backup generator. It is not hard to imagine connecting a similar setup to renewable energy sources to both reduce draw from the electrical grid in normal times, and to supplement backup power in the event of a grid outage.

Financial, Guest, and Staff Benefits

Everyone I spoke with brought up significant financial benefits. There are not enough deployments in hotels to produce solid industry numbers, but the evidence of cost savings is strong. The Sinclair Hotel was an office-building conversion; it achieved 39% energy savings vs. pre-renovation even though the hotel is occupied 24/7 while the office building was mostly empty at night and on weekends. CapEx savings were also significant, primarily from a reduced need for conduit, less need for electrical contractors and materials, 50% fewer electrical and IDF closets, a reduction of incoming power from 3000 to 2500 amps, and decreased construction time.

A lower cost for reconfigurations or future renovations was also noted, even if not immediately recognizable. DC power makes it much cheaper to modify guest room configurations without tearing down walls to move lights and outlets. And just as many hotels install dark (unused) fiber optic cable to meet unforeseen future data needs, some hotels are now running dark low-voltage electrical cable as well. It is getting closer to the day when getting permanent new power to previously unpowered locations will be easily within the scope of the building engineer or IT support, rather than requiring an electrical contractor, drywall repair, and repainting.

PoE-powered devices are easily networked, and they can communicate status to and accept commands from a controller. The control software is flexible and customizable, to the point where one hotel that had put guest-room balcony lights on a timer was able to reprogram them to address a single guest’s complaint, then return them to the status quo after they checked out. But more to the point, buildings with intelligent management systems and connected sensors and environmental control devices can provide more consistent guest comfort, whether from temperature control, lighting intensity and color, air quality, or other aspects. And of course, they can reduce energy usage in more ways than just thermostat setback, for example by adjusting drapes in unoccupied rooms to take advantage of sunlight for greenhouse-effect heating on cool days, or to avoid it on hot ones.


It is time for technologists to play an active role in designing intelligent electrical power solutions for hotels. The infrastructure used in most hotels is decades out of date vs. the need, and is inefficient, inflexible, and unnecessarily dangerous.

However, the technology is complex and evolving. Look at some of these options and talk to the people who are using them and who make them. If you think it makes sense for one of your hotels and you want to move forward, great! But it is complex, and you will need professional design advice (and even then, some trial and error) to get it right. Look for experts (such as the ones mentioned here) who have experience in deploying PoE, Digital Electricity, or both, at least in large commercial or residential buildings if not hotels.

Douglas Rice

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