Over the years, numerous studies have shown that the submetering of utilities is one of the most effective ways to reduce consumption in multifamily properties. Submetering a master-metered building is unlike virtually any other energy conservation measure that can be undertaken by a building owner. Submetering as a conservation measure enlists both management and residents in the effort and generally produces a conservation savings of 20 to 40%. With advancements made over the past years, there now exists a wide range of technologies available to accomplish submetering for water, gas or electric for almost every property configuration.
A brief description of these systems and a typical wireless system is given below. Please note that submetering rules vary from state to state. It is best to check with your preferred billing company before beginning.
There are two primary technologies employed to submeter water depending on how the building is plumbed for delivery of water to each unit. If the water entering an apartment can be captured at one single point for either hot or cold water, a standard ¾ 'conventional' water meter is used.
If there are multiple points of entry for each apartment, then 'Point of Use' technology is used. Each of the plumbing configurations is prevalent in the U.S. with an approximate 50/50 split. Both configurations and submetering solutions are described below.
Electricity is used everyday to heat, cool, and light your homes, as well as power appliances. By practicing some of the conservation tips below, you could potentially lower the cost of your electric bill.
For retrofit units, a typical electric submetering system uses a solid state meter installed at the distribution point of electrical feeds for each unit. The feeds will generally be found in a breaker panel in each unit or in a central distribution panel. The measurement of electrical usage for each unit is achieved by connecting “current transformers” around each feed to measure the current in each electrical feed. The electric submeter, which also measures the voltage of each specific feed, calculates the kilowatt hours (kWh) of energy by a formula using the current and voltage measurements. Once again, these meters readily connect to a standard wireless transmitter. New construction will in almost all cases use a standard socketed, (bubble) electric meter provided by the utility source.
The submetering of gas can take place in a broad array of techniques that once again depends on the system currently installed or is being installed (new construction) on the property. Typically, the largest consumption of natural gas is used for heating. The following describes the submetering solution for the three most common types of heating in multifamily homes.
Units that have an individual furnace for heat generally have two options to submeter the gas usage. The first method is the use of a standard gas meter designed for this application which directly measures the amount of gas. The meters are typically slightly larger than a football and are installed in-line with the gas line.
The second method is with the use of a “run time” device which is connected to the furnace controller. When the thermostat calls for heat, the run time device begins counting. If the furnace rating is known, in BTUs/hour for example, the amount of gas usage is calculated using a fairly straight forward calculation by multiplying the furnace rating by the time the furnace is on. In both cases, the metering device is connected to a wireless system for automatic meter reading.
Central boiler systems use one or more boilers to heat water that is distributed to each unit through a series of pipes. Each unit receives heat when the thermostat calls for heat and opens a “zone valve” that allows hot water to flow through in-unit baseboard registers. In this heating system style, the aforementioned run time device is connected to the zone valve controls and counts how much time each unit calls for heat. The total gas consumed by the hot water boiler, as typically measured by a house meter, is then allocated based on much heat each unit has called for over a period of time. Slight variations of run time devices are available to provide additional consistency in the measurement of heat usage.
Fan coil systems will typically have a central boiler for heat or an in-unit heating and cooling system. Gas submetering in this case is typically done by connecting a run time device across the fan coil controller. Allocation is again done by taking the total gas used for heating and allocating amongst the units based on the run time of each unit. Some run time devices also use sensors to measure the difference in air temperature to do a more direct calculation of energy used. These devices generally are more expensive but can take out some of the variation for this type of submetering.
This type of plumbing is also referred to as a 'stacked riser' plumbing method where a pair of pipes delivers cold and hot water to similar unit configurations that are stacked on each other in a multilevel building. A separate pair of hot and cold riser pipes will generally supply the kitchens in a stacked configuration and another separate pair of riser pipes will feed stacked bathrooms. The pipes typically branch behind the interior walls creating multiple points of entry for hot and cold water to an area.
In this scenario, water usage is most economically metered at the point of use. For example, a single bathroom apartment with a dishwasher would have eight points of use that are metered: three points in the kitchen (one hot feed for the dishwasher and vanity, and one cold feed for the vanity) and five points in the bathroom (toilet, hot and cold feeds in the vanity, the tub and shower).
The smaller sized flow meters deployed at each point of use are generally rated for up to eight gallons per minute and are attached to electronics that convert the flow meter signals into gallons of consumption. The meter electronics interface to a wireless transmitter to allow the meter to be automatically read. In many states, the owner has the option to meter only the higher usage points such as the tub/shower and the toilet to reduce the overall installation cost. Stacked riser plumbing systems are readily identified by a central boiler.
A typical submetering system to automatically read gas, water and electric metering devices consist of three components: