Metering system - Project definition

The step Project Definition shall be realized with the future users of the system and enables to select the main principles of the solution to satisfy the objectives

Define objectives

When designing a metering system, defining the objective is essential to identity customer needs and to define the boundary of the energy monitoring system.

Main applications for an energy monitoring system are the following:
• energy cost allocation
• energy sub-billing
• energy usage analysis
• building energy performance benchmarking
• electrical distribution asset management
• energy consumption alarming
• bill auditing (shadow metering),
• regulatory or label compliance

These above objectives are generic and should be customized for each energy monitoring project

Targeted budget estimate

At the beginning of a project, a short and simple budget estimate can be carried out with a simple payback period – it will dictate the level of effort and adequation with the project goal. This method applies better to existing building, for new building the metering and monitoring cost is embedded in the total investment cost.

- Energy savings: assess the savings according to the actions that will be conducted after the implementation of the energy monitoring system – 10 % is a good default value. The US Department of Energy presents metering related savings ranges based on different used of the metered data

- Payback period : define the desired payback period ( 1 to 3 years)
- Targeted budget : knowing the total energy bill, the budget for the metering and monitoring system and the operation costs can be calculated

Targeted budget = Total energy bill (k€/year) x energy savings (%) x payback period (year)

At the end of the solution design, a detailed cost estimate and cost savings will be conducted in order to tune-up the metering system with the project and calculate the ROI.

Define the performance metrics

Before starting to define any data to collect, it is much more important to define the necessary data to support and to meet the project goals. They are called the performance metrics and are the translation of the project goals into measurable data . They usually are part of the final energy dashboards.

We give here below some examples of performance metrics. A list of general energy performance metrics for a commercial buildingis also given by the National Renewable Energy Laboratory .

Performance metrics for the EPBD compliance

If one of the project goals is to be compliant with the EPBD, two performance metrics which make up the EPC are mandatory for the whole building :
- Energy Efficiency Rating (KWh ep/m².year)
- Environmental impact (CO2) Rating( kg eqCO2/m².year)

Performance metrics for whole building benchmarking

For building benchmarking, we shall consider:
- Main supplies
- Renewable energies production
- Specific energy uses that are normally not typical of that activity sector (called separable energy use) or very different for each building such as laboratories in a university campus, leisure facility in an office building…Including these energy uses may reduce the validity of the benchmark, they shall be deducted from the total energy consumption to compare values of different buildings.

To enable building benchmarking, it is also very important to normalize the consumption.
The data used may differ according to the activity sector, for example the performance metric for the total consumption is expressed in:
- kWh/m² for an office
- kWh/occupancy rate for an hotel
- kWh/ production rate for an industrial building

Data shall also be corrected with Heating Degree Days and Cooling Degree Days to compare the current building consumptions with the previous years.

Performance metrics for Energy usage analysis

Performance metrics can be of type global performance such as global utilities consumptions (Gas, Electricity, Fuel, …) but could also be expanded to analyze deeper the building energy and water consumptions.
If an energy manager wants to understand and to have a clear picture of how energy is used in the building, to track deviations from a target, it is strongly advisable to be able to analyse consumptions per area and energy use.
The first step is then to make a breakdown of the building per physical area of homogeneous activity and major consumption:
- Outdoor
- Parking
- Catering
- Common area
- Tenant area
- …
The second step is to make a breakdown per energy use. Typical energy use breakdown in commercial buildings can be the following:
- Lighting
- Heating
- Cooling
- Ventilation
- Domestic Hot Water
- Other (office equipment, …)

It is then possible to set up the metering strategy and define the performance metrics by selecting which energy use in which area has to be monitored.

	Outdoor	Parking	Catering	Office area	Common area	....
Lighting	X	X		X	X
Ventilation		X		X	X
DHW			X
Cooling				X	X
Heating				X	X
Small power

To be able to put a cross in the right cell, it is advisable to get an idea of the major consumptions in the building thanks to :

•  energy audit
•  building benchmarking
•  calculation with simulation tool

As example, we give here below a list of performance metrics per user for an office building from the white book " Monitoring energy performance"  

Performance metrics for LEED

There are several metering requirement to achieve a LEED label but it depends on the type of project and so do the related performance metrics.

New Construction

• Credit NC2009 EAc5 – Measurement and Verification - 3 points

Measurement and verification (M&V) involves recording actual energy use over the course of occupancy, and comparing that data with the estimated energy use seen in the design.
Performance metrics shall be defined according to the data calculated either by estimation or simulation.

Existing Building in Operation

• Credit EBOM2009 WEc1 – Water performance measurement - 1 to 2 points

This credit requires the following performance metrics:
- Whole building water consumption with weekly data collection --> 1 points
- Sub-metering at the system level with weekly data collection. The qualifying types of sub-metering for this credit are: irrigation, indoor plumbing fixtures/fittings, cooling tower water, domestic hot water, or process water use. --> 2 points

• Credit EBOM2009 EAc3 –Performance measurement - System Level metering - 1 or 2 points

This credit encourages the use of building systems submetering to enhance the ability of operational staff to analyze specific energy loads and to pinpoint potential areas for improvement in system-level or equipment performance.
It requires:
- A breakdown of the largest energy use categories shall be done and cover 40 or 80 % of the total consumption (according ASHRAE energy audit)
- A minimum number of the previous categories to be covered at least by 80%
Metering must be continuous and data logged to allow for an analysis of time trends. The project team must compile monthly and annual summaries of results for each system covered.

• Credit EBOM2009 EAc4 – On site and Off-site renewable energy - 1 to 6 points

Apart from using renewable energy systems, this credit requires also to submeter the energy produced by the renewable energy system in order to show the corresponding percentage of building energy use met by renewable systems.

Commercial Interiors

• Credit CI2009 EAc3 – Measurement and Verification - 2 to 5 points

- Case 1 : project less than 75% of the total building area --> 2 points
The credit requires installation of submetering equipment to measure and record energy use within the tenant space
- Case 2 : project 75% or more of the total building area --> 5 points
Continuous metering equipment shall be installed for several end uses with a Measurement and Verification plan
The performance metrics are then linked to the required end-use categories such as:
o Lighting systems
o Constant or variable motor loads
o Variable frequency drive
o Chiller efficiency
o Cooling load
o Air and water economizer and heat recovery cycles
o Air distribution and ventilation air volumes
o Boiler efficiencies
o Building related process energy systems
o Indoor water riser and outdoor irrigation systems

Performance metrics for BREEAM (UK)

The following metering requirements are mandatory to achieve a BREEAM label:

• Issue Ene 2 – Sub-metering of substantial energy uses - 1 credit

Separate accessible energy sub-meters shall be provided for the following systems :
a. Space Heating
b. Domestic Hot Water
c. Humidification
d. Cooling
e. Fans (major)
f. Lighting
g. Small Power (lighting and small power can be on the same sub-meter where supplies are
taken at each floor/department).
h. Other major energy-consuming items where appropriate

• Issue Ene 3 – Sub-metering of high energy load and Tenancy areas - 1 credit

Provision of accessible sub-meters covering the energy supply to all tenanted, or in the case of
single occupancy buildings, relevant function areas or departments within the building/unit.

• Issue Wat 2 – Water meter - 1 credit

Water consumption shall be monitor as follow:
1. The specification of a water meter on the mains water supply to each building;
2. The water meter has a pulsed output to enable connection to a Building Management System
(BMS) for the monitoring of water consumption.
There is special innovation credit achievable for sub-metering of individual areas where demand in such areas will be equal to or greater than of 10% of the total water demand of the building.