Home Energy Management Systems

HEMS by Google: Google Power MeterWhat a great goal we have: reducing our emissions, and for some of us, saving money at the same time. Energy efficiency is growing more important and getting more attention from all sides. But wouldn’t it all be easier if it were done automatically? The concept called Home Energy (or Power) Management System (HEMS) attempts to achieve this from within our own four walls. But what is HEMS? In a nutshell a HEMS would be a central unit with a graphic interface that controls the energy usage in the different rooms of a house through its sensors.

As a whole, the system is the intricate constellation of different components that can be complex and difficult to build. The components could be energy sources (self-produced energy or bought from the grid); an array of sensors for e.g. temperature, presence of a person, etc; a central control unit along with it’s information terminals; communication unit with the grid, and other smaller secondary components.
A more efficient energy usage can be achieved at home, simply by turning off the lights when not in use. We all know that, but let’s be honest, how many of us leave them on for a couple of minutes or once in a while we fail to close the fridge’s door tidily so it won’t stay open all night? This is where HEMS kicks in by turning off and on the lights by itself, or alerting you that the milk will go sour if don’t close the fridge’s door. After some time it learns that people go to sleep at midnight, so it won’t power those appliances on stand-by. If you have a day/night tariff, it will switch on power hungry appliances like the washing machine when electricity is the cheapest. The whole system relies on sensors, and the statistical data collected from them.

There are many companies out there offering one or more of the components, but almost none of them offer them all as one package. In Japan, Daiwa House Industry has been a pioneer in this field, having begun to offer houses with preinstalled HEMS, together with photovoltaic cells and Li-ion rechargeable batteries. These houses will sell for approx. USD 600’000 (JPY 54 million) starting spring 2011, compared to USD 375’000 (JPY 34 million) for a similar home with no HEMS. Regardless of real estate being normally more expensive in Japan, that’s quite a hefty difference. It definitely makes a buyer think twice whether or not to get HEMS. For those of us who don’t have the change for a complete package, putting all the components together could be a challenging DIY task. There are many companies out there making their way into the market at a rapid pace, with some big companies’ like Microsoft Hohm or Google PowerMeter, the market might soon get quite competitive.

As the market expands and initial cost decreased we might be able to save on energy bills and lower our footprint in our own home without much effort. That is not including the effort of having put together and installed the system ourselves…


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