In commercial real estate, metering is the best way of getting more information about what’s going on in your building. Every optimization project, from simple changes in the building’s heating schedule to major renovations, is more likely to succeed if the team behind it has access to detailed information about building utility flows from meters and submeters.
This guide is intended to tell you everything you need to know about what is possible with modern metering and submetering. With actions informed by a detailed look at the way utilities move through your building, it is possible to significantly reduce their consumption in some cases and shift necessary use to cut operational costs in others. Other types of meters give building engineers information about the quality of air in a tenant space to assist in efforts to make the space more comfortable and safe. Since the advent of “internet of things” technology, advanced metering has become more affordable, opening up new business applications in commercial real estate.
The Case for Submeters
Before we get into how different meters can be installed, we should discuss why a building team would want meters that are more advanced than the ones that come standard with a utility connection. Every operational commercial building or complex must have building-level meters installed in order to access public water, gas, and electricity. These meters give a measure of utility consumption for the entire structure and are often read once per month or less.
Installing meters at one or more levels below the building-level meter (a.k.a. submeters) gives you a more granular look at what’s going on in your building. A submeter installed for each tenant space lets you bill tenants for the resources that they actually consume, instead of dividing total consumption by floor space, giving them an incentive to conserve. This also provides the building team with backup when a tenant complains about a bill, and makes it simple to track unusual consumption spikes down to their sources.
Similar to this last point, submeters installed to monitor large building equipment, like HVAC systems or cooling towers, ensure that your team will know early on if there’s a problem. This last point is especially important; millions of dollars are frequently saved in a day because a serious leak or fire hazard is detected.
Meter Types and Scoping
The first step to installing advanced meters throughout a building is scoping. This involves taking stock of the level of detail that the building team wants and assessing the existing infrastructure in the building. If the team is happy with the current level of resolution that is being tracked in the building – whether that resolution is at the building level or deeper – then the only thing that has to be done may be to connect the existing meters to a wireless gateway. A building team looking for more detail might want meters installed to measure tenant consumption, to track energy and water used by large equipment, or even to individual spaces within a larger unit.
When new meters have to be installed, the scoping process involves choosing the correct meters to use based on the utility being measured, cost, and the specifics of the building’s layout. Below is a brief overview of the options for each utility.
The most common way to measure electric current is by using a current transformer, usually called a CT. CTs consist of a loop of wire that is wound around the device a variable number of times. When connected to and placed around a wire carrying an alternating current (the primary), this produces a smaller, proportional current in the loop of wire (the secondary) that is easier to measure with an electric meter like an Emon or Rail 350.
CTs are used for measuring current at every level, from the power grid to relatively small loads in buildings. Because the current in the secondary is proportional to the current in the primary and the number of “turns” wound around the device, CTs can be very large or very small, depending on what they’re designed to measure. In some industrial settings, individual components of a machine might be metered using their own CT. In a commercial building, individual floors, tenant spaces, and important pieces of building equipment are often metered.
Water, Gas, and Steam
There are three primary options for measuring flow: in-line meters, insertion meters, and ultrasonic meters. Within the first two categories, there are several options for each type of utility. For example, the most common in-line gas meter is a diaphragm meter, which directs the flow of gas with internal valves and chambers, but there are also rotary meters and orifice meters for other situations. Steam has the most options because it can be measured directly or the condensate produced by steam cooling can be measured.
In-line meters are the most affordable type of meter to purchase for small pipes, but they are generally the most difficult to install. As the name suggests, this type of meter is installed in-line with the water pipe, meaning that the flow of the utility has to be shut off during installation. A section of the pipe then has to be removed and replaced with the meter. When the water, gas, or steam is turned back on, it passes through the meter and is measured. In-line meters are also fairly expensive for pipes that are greater than 3” in diameter.
Insertion meters are small rods that are inserted into a pipe through a hole and held in place by a saddle. Because they only need a small hole, the flow can be left on and the rod can be inserted (quickly) in a process called a “hot tap.” Compared to an ultrasonic meter, insertion meters only require a small section of pipe (though they do need more than in-line meters). Inside, the rod may hold a small turbine that measures flow or it may rely on a more complicated technique.
Ultrasonic meters are usually more expensive to purchase than other types of flow meters, but they are considerably easier to install. Where they are an option, this usually makes them the most cost-effective option overall. They consist of two bands that are a pre-set distance apart from each other and a central display. The bands send ultrasonic pulses between each other and calculate flow through the pipe by measuring the speed of each pulse. The downside to ultrasonic meters is that they generally require a straight run in the pipe that is 20x diameter before the first band and 10x to 20x diameter after the second band, which is not always available.
Measuring the amount of HVAC energy going to multiple locations in a building from a single unit generally requires a BTU meter, which consists of a flow meter and two temperature sensors. The flow meter measures the rate of flow of the working substance – often water – and the temperature sensors measure the heat in the working substance as it enters the tenant space and as it leaves it.
Armed with knowledge of the working substance’s density, specific heat, and the data collected from the sensors above, the amount of energy consumed in the heat exchange process can be calculated with the following formula:
Where: Q = heat exchange, V = volume, Cp = specific heat, ρ = density, Tsupply = incoming temperature, and Treturn = outgoing temperature.
Collecting Data From Meters
Having that data isn’t much good if you don’t have an effective way of accessing it. In many buildings, engineers still have to perform the familiar monthly rite of walking to each meter in the building, clipboard in hand, recording the numbers on the outside of each box. This process is time-consuming and extremely error-prone. In particular, the clipboard approach is vulnerable to systematic errors that can cause significant losses, especially when multipliers are involved.
Fortunately, there are modern solutions to this problem that circumvent the long-walk-with-clipboard entirely.
Many meters are pulse enabled, which means that they convert their data into digital pulses for output. For example, a pulse-enabled electric meter might be configured to send a pulse for every kilowatt-hour that passes through the wire it’s measuring. The computer reading the pulses knows that, if 20 pulses are read in an hour, the building used 20 kWh in that time. These pulses can then be routed to a digital gateway that sends them over the internet to a computer waiting to interpret them.
More modern meters may use a communications protocol like Modbus to transfer information instead of pulses. This approach is more reliable and allows for more detailed information to be transferred than just consumption data.
Utility companies will sometimes give customers access to “interval” data online. This is utility consumption data that is provided at a regular delay – often about a day. This is pretty basic, especially because the utility usually only considers building-level data, but it can be useful for tracking consumption against targets throughout the month.
Real-time data is even more useful. Most modern energy management systems pull data from meters and transmit it over the internet to the cloud. There, it can be presented in up-to-the-minute detail. This makes it possible to do things like sending alerts when something is behaving abnormally, investigating usage spikes while they’re happening, or making adjustments to operations in real time.
Viewing and Analyzing Meter Data
Getting data out of meters is only half the battle. Presenting that data in a way that is intuitive and that leads to actionable insights is at least as difficult of a technical challenge.
Modern energy management systems generally use a digital platform to present the data they collect from meters and submeters. The most basic visualization is an energy curve, which is the shape made by a building’s energy consumption over the course of a single day. The ideal energy curve for a standard office should rise quickly in the morning from a low baseload, stay relatively flat throughout the working day, and fall back to the baseload after hours. In practice, there are some common deviations from this curve that are good targets for efficiency projects. The use of other utilities often will follow a similar pattern.
Another basic tool is budget tracking, which plots your consumption against your budget on a monthly, quarterly, or yearly basis.
The next step is decoding your building data to find valuable insights that you can act on. This is where data analytics come in, and it’s here that higher-end energy management systems set themselves apart from the competition.
Applying data analytics to utility consumption data creates powerful tools like weather normalization, which combines weather forecasts with historical data about how your building performs in different conditions to predict a range in which it will perform today. This sets your building’s utility consumption in context; an average energy curve on a perfect day might mean that HVAC units are working harder than they should, for example, but slightly higher than average curve on an especially hot day could still represent an efficient use of energy. Analysis of the same data can also help an energy management system to recommend startup and shutdown times that match the specific needs of your building given the day’s weather, helping your team to shave off energy costs every day.
The Future of Metering
As time goes on, new and better metering technology will be introduced. We’re already seeing meters that measure new variables, like CO2 and other air quality indicators, making their way into buildings as costs come down. While environmental sensors won’t help building teams to reduce utility costs, some tenants find them valuable for the productivity gains that they facilitate. Low air quality is associated with lower employee productivity and a higher number of sick days taken.
Traditional meters are also improving and becoming more affordable, meaning more profitable use cases will become available. For example, submetering is mostly limited to important pieces of building equipment and large (usually commercial) tenant spaces at present. This isn’t a technical problem – submetering is just generally too expensive to be worth it for smaller spaces. As meters become more affordable, the resolution with which teams can manage their properties will increase.
A little bit further away, but potentially more useful in the long run are advances in analytics that could allow algorithms to make operational changes to buildings automatically based on meter data. As algorithms improve, more and more steps will be trusted to the computer. Eventually, buildings could become a closed loop, allowing their human teams to focus on repairs, maintenance, and relationships with tenants while utility use is optimized by a computer.