Thursday, August 6, 2009
Energy Management systems allow homeowners back in the drivers seat
If you’ve ever driven a Toyota Prius hybrid, you know the car’s dashboard includes a monitor that displays which power source is operating and how many miles per gallon you’re getting. The functionality has spawned a practice called “hypermiling,” in which drivers squeeze every little bit of fuel efficiency out of their cars by making adjustments to the way they drive.
Now homeowners can do the same thing. An array of manufacturers offer residential energy monitoring and management systems that serve much the same purpose. These “dashboards” give feedback that homeowners can use to maximize a house’s energy and resource efficiency, and help your homes live up to their performance expectations. And some manufacturers are adding even more advanced features that will help them monitor and control the sources and use of resources.
At the most basic level, energy monitors provide a simple readout of the total amount of energy the home is using, often by attaching a sensor to the electric meter that sends a wireless signal to the in-home display. The monitors may show the dollar cost of the electricity based on electric rates that the user enters or may let users monitor energy usage by day or time.
Research has shown that even such basic feedback can lead to savings. In a 2006 paper “The Effectiveness of Feedback on Energy Consumption” for the University of Oxford, Sarah Darby says the literature demonstrates “that instantaneous, direct feedback in combination with frequent, accurate billing is needed as a basis for sustained demand reduction.” She adds that the norm for energy savings from direct feedback is 5% to 15%, and studies using a table-top interactive cost and power display unit have shown savings as high as 20%.
“If you can see it on a display, people then take a real interest in lowering [energy] demand,” says Keith Davis, president of Residential Technologies, a Charlotte, N.C.–based electrical and electronic systems contractor. “Having knowledge allows them to control energy use within their budget and financial means and within their lifestyle.”
No matter how carefully you plan for the operation of your homes, the occupants’ lifestyles and habits determine the buildings’ ultimate performance. Energy management systems can help customers achieve the energy efficiency they thought they would get from a green home.
Beyond basic whole-house monitors, installers can turn to packaged monitoring systems that offer more detailed feedback or to control systems that let homeowners automate energy-saving tasks.
While simple, whole-house monitoring can lead to proven energy savings, builders and remodelers can help homeowners fine-tune their homes further with energy management systems, such as Agilewaves or EcoView, that give feedback on individual systems or resources like gas and water. Agilewaves, for instance, has a resource monitor that can track individual electric loads, rooms, or floors of the home, or alternative power generation, in addition to gas and water.
For example, one Agilewaves customer installed a powerful solar array and discovered his inverter was failing at peak production—data he most likely never would have seen otherwise, says company chief technical officer David Brock.
Adding to the options are home control systems and intelligent HVAC controllers that not only monitor the energy a system uses, but also control settings based on occupancy, temperatures, or the cost of energy at a given time. Such systems, including Control4 and Crestron, are better known for their home theater and “smart home” controls, but some are now set up to integrate energy monitoring features, and at a more reasonable cost than luxury systems of the past, acccording to Bill Ablondi, director of home systems for research firm Parks Associates.
These systems build off such useful but underused technologies as programmable thermostats and lighting controls to also monitor the energy used by the products they control and provide feedback. In short, they make it easier to operate the home at peak performance. While they face many of the same challenges as home automation systems—builders may be unwilling to add to the home’s initial cost, and the systems might intimidate less tech-savvy homeowners—they can be a differentiator.
Homeowners can now operate and manage control and monitoring systems in a variety of formats, from the traditional wall-mounted touchscreen to a Web application to mobile phones or devices. Many of the companies offer e-mail or text alerts when certain energy or carbon footprint thresholds are met and can automatically take action, such as setting back the temperature, to decrease the load.
The systems vary in how they monitor usage. Some use individual load sensors that track the electrical draw of a device—a more accurate but more expensive method. Others simply calculate predicted energy use based on runtime and settings for a device.
Proving a return on investment is still an obstacle. At $500 for an entry-point controller and several thousand dollars for a full home control system, payback at current energy prices is six to eight years, says Eric Smith, chief technology officer of Control4, though he adds the company is working on a basic package that would cost less than $250. Agilewaves’ typical whole-house gas and electric monitoring system with details on seven circuits retails for $7,500, and prices can range higher or lower depending on capabilities.
Home energy hypermilers also will ask about the systems’ own energy use, which varies depending on the device. Brock says Agilewaves has been conscious about the resource monitor’s energy draw, and that the system pulls up to 30 watts at maximum.