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What is a Smart Meter?

A Smart Meter is an electronic device which is used to provide detailed real-time information about your energy usage. Smart Meters can tell you the real-time cost of energy, so that you can plan your energy usage to be more cost effective. Smart Meters can also tell you where you use your energy and help to improve your energy efficiency.

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What is the difference between cheap energy and expensive energy?

The cost of energy is affected by the demand for energy at a moment in time. During peak hours, when energy demand is higher, the cost of energy per unit is more expensive. During off peak hours, when energy demand is lower, the cost of energy per unit is cheaper. Choosing to run electrical appliances such as dishwashers and tumble driers during these hours can reduce the overall cost of your energy bills.

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How could OCTES benefit me?

OCTES could help you to understand where the cost of your energy usage comes from, and how to reduce both the amount of money that you spend on your energy bills and the amount of energy that you use. Visit the OCTES Service tab for information on the OCTES Service and links to useful documents produced through OCTES.

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Electrical Energy Monitoring

Utility companies have used electro-mechanical meters for a long time to measure electrical energy used by their customers and for billing them. Although these meters are accurate, reliable and robust they only show power usage and the reading must be made manually.

When electronic meters with microprocessors were introduced they were considered smart as they could perform calculations like calculating the; average power, power factor, reactive power and maximum power. At first this information could only be read from the LCD display on the meter but during the last decade information and communicaton technology (ICT) has been added to the electronic meters. These electronic meters that can send the information to the utility companies for revenue billing. But, their potential is much more. Smart meters play a fundamental role in all discussion and development of the smart grid. The smart grid is an electrical grid where the information about usage of consumers and the power production of utilities is communicated and used to improve the electrical grid; e.g. load distribution, efficiency, peak leveling and reliablility. The information can also be used as marked drivers where supply and demand decide the energy prices. The smart meters provide the information data which is then processed using AI and control techniques and used to control the grid.

There are many definitions for smart meters. The main difference is how advanced the meters are. Here the following definition used:

A Smart Meter is an electronic measurement device used to measure electric power consumption and communicating it using information and communication technologies.

The communication level can be from one way communication where the meter sends the collected data to the utility company. When smart meters are used in this way the system is called an Automated Meter Reading (AMR) systems. The meters can also have a two-way communication with the utility company and be a part of a more advanced system where they take a part of the monitoring and control. Such systems are called Advanced Metering Infrastructure (AMI) and will be a fundamental part of the Smart Grid.

The smart meters can communicate data using several protocols; e.g., the information can be sent via telephone lines, GSM, GPRS, wireless, infrared, internet and also the power lines. However, as always when personal data is transferred and processed the security of the data must be considered; i.e., it is possible to deduce from usage data when a consumer is away from home.

Smart meters and smart metering systems can also be used by energy consumers for monitoring their consumption. Measuring the consumption is a prerequisite if one wants to improve it. By monitoring the electric energy usage the consumer will be more aware of his usage and can work on ways to transform how the energy is consumed. Some systems can also help the consumer to stay within a budget; i.e., they can issue an alert when the usage reaches a predetermined limit. Some systems even cut out electric appliances to prevent the consumer from exceeding the limit. Meters and systems made specially for this purpose for utility customers are often called home energy meters or home energy monitor systems depending on how advanced the systems are. These systems do not need to have to be the same accuracy or robustness as the systems used for revenue billing. For this reason home energy monitor systems are generally cheaper than the ones that are used by the utility companies and many can be installed by the consumer; i.e., installation does not require a certified electrician.

However, the monitoring systems are constantly being improved and today the most advanced systems can be used to monitor the quality of the electricity; i.e. surges, and for studying the utility bills and if necessary dispute them. Increasing the consumer awareness will not only lead to lower consumption it will also put a pressure on the utility companies to provide better service. Better service can include higher quality electricity and more frequent utility bills with more detail - similar to the bills issued by the phone companies.

Home energy monitoring solutions
The different types of home energy monitoring can be divided into three main groups. The following is a description of the groups and a brief discussion about their pros and cons.

Type A – Plug-in Meters
Plug-in meters are mainly for monitoring individual electrical appliances. The meters have a LCD display where the main electrical power quantities can be read; e.g., watts, power factor and min/max readings. Many meters allow the users to program the energy unit cost in order to see the actual cost on the display. Later and sligthly more expensive models have communication ability like WiFi. This means that many plug-in meters can be used and the data collected and processed. The meters are plugged into the wall socket and the electric appliance to be monitored is plugged into the meter. By using an electric extension cord with more than one plugs the total usage of many appliances can be used as long as the maximum load is below the maximum wattage rating of the meter.

Example: Energy Monotoring Socket 2.0 by efergy (www.efergy.com)

Plug-in meters are relatively inexpensive, easy to operate and do not require an licensed electrician for installation. The plug-in design means that the meters measure both voltage and ampers and can therefore calculate real power, apparent power, phase angle and the power factor. By using plug-in meters with communication ability one can setup a house energy monitoring system where one computer processes the information sent from all meters and displays the results.

Since plug-in meters need to be plugged it is not practical to use them to monitor the total electrical consumption of one household. Furthermore, the plug-in meters have a relatively low wattage rating (1500W 2500W) which means that they cannot be used to monitor appliances such as baking ovens and water heaters.

Type B – Energy meters
Instead of measuring the energy consumption directly, energy meters monitor the energy measurement unit installed by the utility company. The monitoring is performed by either monitoring the rotating disc in the electro-mechanical utility meters or reading the LED pulses on the electronic utility meters. The rotating speed of the disc and the rate of the LED pulses are proportional to the power consumption. By monitoring both, counting and determining their rotating/flashing rate the energy meter can calculate your consumption.

Example: PowerCost Monitor by Blue line Innovation (www.bluelineinnovations.com)

Energy meters are relatively cheap systems and the installation can be performed by the house owner. The installation does not require any wiring inside the circuit breaker panel except the low voltage connections used by the meter itself. Therefore the installation does not require a licensed electrician. Since the meters operate by monitoring the utility meters they do not have any maximum limits on the power being monitored and the whole household consumption can be monitored.

Counting LED pulses or revolutions of a rotating disc on the utility meter has its drawbacks. First, the energy meter cannot monitor individual appliances in the house because it can only monitor the total consumption as indicated by the utility meter. Second, the meter cannot calculate calculate power quantities such as power factor or phase angle because it does not measure voltage nor current. Third, the accuracy/resolution is is rather limited especially in the case of counting LED pulses.

Type C –Home energy monitoring systems

Home energy monitoring systems consist of one or more energy meters which communicate the measured data to a processing unit. The processed data is often sent to a in-home display; e.g., a LCD display, but some systems can be plugged into the home network and then the data can be accessed by any web enabled device connected to the home network.

Home energy montoring systems can be divided into two groups; Non invasive and invasive systems. Invasive in this sense means that the installation of the meters requires one to unscrew/unplug electrical wires but non-invasing does not.

Invasing monitoring systems
The installation of the energy meters requires a licensed electrician because the meters are installed inside the circuit breaker panel by accessing the live wires. There are few different setup possible. One is to use a single meter and measure the circuit breaker of interest – e.g. the total consumption. Another setup is to use a set of meters and monitor the energy in selected circuit breakers. Third setup is to monitor the consumption in all the circuit breakers in the house.

Example: eTactica by Remake Electric (www.remakeelectric.com)

The home energy monitoring systems provide the user with the most detailed of the house consumption.

By connecting to the circuit breakers (some systems provide their own breakers) both the voltage and current is measured the real power, apparent power, phase angle and the power factor can be calculated. The load on the circuit breakers can also be monitored and action taken if the nominal load is too high. With adequate data acquisition the waveforms of both the current and the voltage can be acquired and analyzed. With data logging and advanced software solutions it may be possible to identify some appliances and generate a usage profile for them.
Web access to the data means the consumer will be more aware of the electricity usage. Some systems provide web access to the usage data outside from home and even smart phone apps.

Home energy monitoring systems with circuit connections are the most expenisve energy monitoring solutions. In general, the price increases with increasing capability of the system; e.g., number of circuit connections, sampling rate and software capabilities. Furthermore, the circuit based systems require a licensed electrician for installation.
Easier access to data has also some drawbacks; e.g., the security of the usage data and also that installation of the system may require certain networking knowledge.

Non-invasing monitoring systems
Non invasive home monitoring systems use different types of meters; e.g., plug-in meters (see above), energy meters (see above) and meters that estimate the power consumption based on the current in the circuit and a fixed voltage. For measuring the current amp-clamps are put around the live wires.

Example: EnviR by Current Cost (www.currentcost.com)

The meters used in non-invasive monitoring systems are relatively cheap in comparison with the circuit based meters and the installation can be carried out by the house owner. The installation does not require a licensed electrician because the meters do not require any dismantling inside the circuit breaker panel nor of any other live electric wires. Non-invasive monitoring systems are ideal for house owners who want to monitor their consumption but do not need the details.

Only the plug-in meters can provide necessary information to calculate power quantities such as the power factor and the phase angle. The LED based meters can only estimate power and the amp-clamp meters have only information about the current. The accuracy of the system is not high and the total metering system can be rather involved especially if plug-in meters are used.

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