We get asked this question many times especially by new partner energy professionals. In reality, there is not a fixed procedure or magic formula that works in all cases, the number of monitored points (i.e. sub-meters) to deploy depends on many variables. However, here are a few tips that should help you assessing a ballpark number of monitored points that you should consider for your saving projects.
The first question to ask is: what is the objective of installing these meters?
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Case 1: Energy Performance Contract
If the scope is to have an energy performance contract then clearly, the area, machine or device to upgrade must be monitored to identify the efficiency generated by the upgrade. In addition, it may be necessary to monitor other circuits, machines and performance factors that are related and that the upgrade might affect. So the number of meters to install really depends on the type of contract. What we generally see is that the meters installed are usually between 1 and 5 per project.
Case 2: Energy saving strategies and awareness
Often we see that the energy management platform is used to actually scope a number of potential saving projects and relative saving forecasts that are then assessed by the managers. In this case, the energy management system has a significantly higher number of points than in the previous case and it is used to develop an action plan towards the achievement of an ISO50001 or a LEED certification.
In parallel, the objective here is to create awareness and behavioral change of occupants and employees, which also requires a granular energy breakdown to better highlight consumption of areas and major appliances. A strategy that we have encountered is to elect one or more energy champions for the various departments and areas that drive energy saving actions and keep the teams motivated.
In the industrial sector, it is not unusual to encounter plants that install tens or hundreds of monitored points. From what we see, the number of points has a clear relation with the kWh demand of the plant, e.g. around 10 monitored points if the plant has a consumption of around 100MWh monthly or hundreds monitored points if the plant has over 500MWh consumption monthly.
In the commercial sector, the number of monitored points is generally less but the rule of thumb when calculating the average meters installed based on the kWh demand is still valid.
For example, a hotel with an energy management system uses around 300 MWh monthly demand (e.g. 300 rooms, 15 stories and 20 rooms per floor) generally gets equipped with around 15 sub-metering points to monitor each floor, plus another 10-15 points to monitor, kitchens, bars, AHUs and lighting for the major areas of the hotel.
Figure 1: Expected Load vs. Actual Load of monitored points
Case 3: Calculating the number of monitored points based on potential savings
An interesting way to estimate the number of monitored points in a site is to take a 5% of the annual energy bill of the site and using that as a total cost for the energy management system to install.
In fact, studies have shown that a proper use of an energy management system can well exceed a 5% reduction of the annual bill and breaking down consumption helps to identify culprits. Therefore, it makes sense to focus on installing a good amount of meters within a 5% budget to still maintain a one-year payback period for your client.
Are you engaged in an energy savings performance contract, but not sure how many meters your site/ facility requires? Wattics can help.
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