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Chapter 9

Home Energy Management Systems

Introduction

Home energy management systems (HEMS) are rapidly gaining popularity around the world as the technology behind them improves and as small-scale solar power and battery storage become more viable. This section looks at what home energy management systems are and what they can (or should be able to) do.

Definition of HEMS

Like anything, the definition for ‘home energy management system’ will differ slightly from source to source, but we believe the below neatly encapsulates the concept without being too broad.

A home energy management system is a technology platform comprised of both hardware and software that allows the user to monitor energy usage and production and to manually control and/or automate the use of energy within a household.
A photo of the carbonTRACK smart Hub and smart plug
Hardware

A home energy management system’s hardware usually consists of a ‘hub’ device which relays communications between the goings on inside the house, the user and in some cases the local utility or electricity retailer. This hub is usually installed on the home’s electrical board, but may also be installed ‘virtually’ in cases where the HEMS operates purely on a wireless network. Other, less essential components may include ‘smart plugs', light & temperature sensors, and smart devices within the home.


Software

The software used in a HEMS is what moderates the ingoing and outgoing data and communications. From a user’s perspective, the software is the interface that allows access to monitoring data and control functions of the system. The interface usually takes the form of an app or web portal. The software for some HEMS has the express goal of increasing the energy effectiveness or efficiency of the household, while the focus of others is simply to control devices remotely or automatically for convenience or security purposes.

As for monitoring, the sophistication of the way in which the data is displayed will vary, but will usually include some variation of the below:

  • Device & appliance data – Which devices are on and off? How much energy is each one using?
  • Granularity of time data – What is the smallest time increment that the system keeps track of – Do you see live data of your electricity usage or do you see intervals e.g. data every hour.
  • Insights delivered – Does the system send notifications to tip off the user to trends and issues that they may not pick up on without parsing through the data themselves?

As for control, a HEMS may allow a user to do a range of things, including:

  • Turn devices on and off remotely
  • Set devices to operate on schedules
  • Set up conditional rules for device operation
  • Manage the flow of energy from solar panels (and other generators) through the home or in and out of batteries
  • Allow ‘machine learning‘ to take over and run the system semi-automatically
CarbonTRACK desktop dashboard and mobile app
What does a HEMS monitor and manage?

Home energy management systems can vary greatly in the breadth of their applications. There are four main aspects of home energy that a home energy management system can be involved in. Some HEMS operate with all four, while others may only work with one or two. We’ve outlined each of them below.

Electricity

The core functionality of a versatile home energy management system involves the use of electricity within the home. A HEMS should give the user the ability to ‘see’ what devices are doing and to remotely ‘reach in’ and turn them on & off or otherwise modify their operation (e.g. turning down the thermostat temperature on an air conditioning unit).

Provided that the HEMS is geared primarily to save the user money, key considerations in electricity use management will include grid electricity rates, whether the customer is on time of use billing, and whether there is solar power or batteries available on site.

A HEMS may also be required to operate in an off-grid scenario, in which case its role is even more crucial in ensuring that energy is used effectively so that it is always available when required.

Solar PV

Solar PV systems (see Chapter 7) have become commonplace in many countries, allowing homes to generate a portion of their electricity on-site. Depending on the situation and the incentive structure, a solar system owner may make it a priority to ‘self-consume' their solar energy directly or to export it to the grid as much as possible.

A HEMS can show the user how much solar they are generating, using and exporting back to the grid. This information lets users change the times they consume energy at home to make the most of their solar.

The presence of solar battery storage (see below) makes the equation even more complex – making a home energy management system an even more attractive option than for a home with no on-site generation.

Battery storage

Battery storage (see Chapter 8) is the next frontier in home energy, holding the key to greater home energy self-sufficiency and lower electricity bills – not to mention the future of our electricity infrastructure itself. In order to maximise the value of a battery bank, however, it helps to have an intelligent management system that can take into account multiple variables – such as whether you’re on a time of use of flat rate tariff (see section 2), and whether you have any incentive to sell stored energy into the grid.

Solar thermal

Solar thermal – or solar hot water – is a popular technology that uses the sun’s power to heat water within a home (see section 5). Solar hot water system often operate mostly independently of the rest of a home’s electrical devices, but a smart HEMS with the right connectivity & monitoring functionality can help to improve their value even further.


What to look for in a HEMS

There are five essential features every home energy management (HEMS) system should come equipped with. We look at each of them in detail below.

Monitoring

You should be able to log into your HEMS’ user interface (usually a web browser or smartphone app) from anywhere and see what devices are on and using energy in your home. For example: Did you accidentally leave the heating on? Did you forget to turn on the dishwasher? A HEMS should also allow you to view historic data to identify trends, changes and opportunities for improvement.

Control

In addition to allowing you to see what’s happening with regard to energy in your home, you should also be able to take action, manually turning devices on and off or automating their operation with timers or algorithms. Furthermore, you should be able to take these actions from anywhere you have access to the Internet.

Insights

Your HEMS should tell you the story of your energy usage in a way that you would not have otherwise been able to work out. For example, what devices in your home are drawing power on standby when you’re not home? Are you running your air conditioner or heater more than necessary (see section 4)? Are any older devices in your home accounting for a disproportionately large portion of your energy bills – and may need replacing? A HEMS should be able to help you answer these questions – and more.

Integration with solar and batteries

A home energy management system will allow you to monitor and manage not only the energy that you use, but also the energy that you generate (and store), in the most cost-effective way possible. Your HEMS should know whether it will save you the most to pull energy from the grid, your batteries, or directly from your solar panels when the sun is shining.

If you don’t have solar or batteries, your HEMS should be able to help you to size up a system that is well-suited to your needs and budget – after helping you to identify and eliminate inefficiencies within your home.

We hope you found this guide useful! We’d love your feedback on the guide, and suggestions for additional information we could include in the guide is very welcome. You can send us your feedback here.

About carbonTRACK

carbonTRACK is an energy management and Internet of Things (IoT) comapny that helps businesses and households to use less power to save money and the environment.

We envision a world where energy is consumed sustainably, shared fairly, and everyone is empowered to control their energy use.

Our mission is to develop intelligent energy solutions that empower people and engender sustainability through creative technologies.

Guide Contributors

Authors: Rooj Kitisarn & James Martin

Designers: Luke Petering & Gabrielle Rea

 

Congratulations on making it through this guide! If you’re still curious about how a HEMS can help you, have a look at our how it works page.

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