The Difference between HEMS and HANS

I presented a session on Home Energy Management Systems (HEMS) Opportunities and Challenges last week, and one attendee commented that he had not previously heard of HEMS as separate components from Home Area Networks (HANs).  Too often the term HAN is used to describe all the intelligence and activity that occurs in Home Energy Management.  The differences between HEMS and HANs are easily explained, and help everyone as electricity consumers understand new technologies that will be appearing in our homes in the next few years. 

Much like the familiar LANs or Local Area Networks, HANs are simply the same communications capability within a home.   Here is the definition of a HAN from the Smart Grid Dictionary:  “A network of energy management devices, digital consumer electronics, signal-controlled or enabled appliances, and applications within a home environment that is on the home side of the electric meter.  It can also be considered as a home-based LAN, but it connects more than just computers.  HAN specifications include Zigbee, HomePlug, Z-Wave and Wireless M-Bus (a wireless variant of M-Bus).” 

Instead of a network of servers, printers, copiers, and computers, the HAN connects devices that are capable of sending and receiving signals from a meter, In-Home Displays (IHDs) and /or HEMS applications.  While it is unlikely that in the future my refrigerator has anything interesting to say to my dryer, both devices should communicate with a smart meter or an IHD to identify start times or learn operation parameters that were set up by my HEMS application. 

Wired or wireless, there are tradeoffs that involve power consumption, signaling distance, sensitivity to interference, and security.  The main point here is that HANs are not energy management applications – they enable energy management applications to monitor and control the devices on the home network. 

HANs and IHDs still need an energy management application – a HEMS solution – in order to gain the most benefit from these Smart Grid components.  IHDs are great devices, but have limited data input and display capabilities – in fact some do nothing more than provide a visual indicator of the electricity rates at any point in time.  A HEMS web portal is the best interface to the utility billing and Demand Response programs – it enables the easiest designation of intelligent appliances that can be “enrolled” into utility demand response programs.  The HEMS solution allows me to “set and forget” my appliances’ operations, get suggestions on energy efficiency improvements, and see how my energy management compares to others in my peer group or neighborhood.      

What are the other features I’d like to see in a HEMS solution? 

  • Open, non-proprietary, and standards-based software
  • Simple and intuitive user interface
  • Delivers user-definable information to a selection of IHDs
  • Support for IHDs that combine HAN gateway and HEMS display capabilities
  • Controls any manufacturer’s intelligent appliances
  • Contains HAN diagnostics
  • Easy to deploy and upgrade
  • Secure access to utility billing system to view bills
  • EV charging management
  • Micro generation and energy storage management and diagnostics

Some of these capabilities are available now from a number of HEMS providers, but others are future capabilities and will be for quite some time.  I’ll talk about other desirable HEMS capabilities in next week’s blog.