Data Loggers Identify Hidden Energy Waste
June 19, 2012

Your utility bill is a great indication of energy consumption, but it says very little about energy usage. If you want to get a clearer picture of that, add a new device to your toolbox.

“Effective energy management is data-driven,” says Paul Stiller, director of energy management at Summit Energy Services. “Each building is unique and you need the specific facts for it.”

Record Data
“Data loggers can be configured in a variety of ways and deployed many times,” Stiller says, adding that different types can measure temperature, relative humidity, CO2 levels, motor run times, electricity usage, and on/off cycles.

“You want to make sure building systems perform as efficiently as they were designed to, because in most cases we find that they don’t,” says Gregg Daly, director of sales for manufacturer Onset Computer Corporation.

A data logger costs under $100, but you’ll likely need three to five kinds for the different systems in your facility. Once configured to your computer, data loggers are attached to the system via magnetic strip, which then detects the magnetic field generated when a system is turned on.

Data loggers show specific system-by-system statistics, allowing you to hone in on inefficiencies.

The Vermont Community Foundation in Middlebury, VT, consulted Kilawatt Technologies to deduce why its 9,000-square-foot facility generated $25,000 in annual utility costs – a high price to pay at $3 per square foot considering the facility’s relatively new HVAC system.

Kilawatt utilized data loggers and collected more than 250,000 measurements over a three-week period.

Detect Problems
“Systems can go faulty at any time,” says Evan Lubofsky, director of marketing for Onset. “They can fall out of tune relatively quickly and easily, and data loggers help you get them tuned back up.”

At the Vermont Community Foundation, data loggers revealed that heat and circulation pumps, as well as loop motors, ran during nights and weekends when the building was unoccupied. Temperatures in office areas did not coincide with thermostat settings, and CO2 spikes during occupied hours indicated poor ventilation.

These problems are relatively common, regardless of building type, age, or location, Daly says.

“It becomes very simple to see these issues when you log the data and plot out your graph. It doesn’t take very sophisticated analysis,” Lubofsky adds. “The software’s tools help you interpret the data and act on it.”

Make Changes
“You can’t manage what you don’t measure, but remember that measuring is not managing,” advises Stiller. “Data loggers in your toolbox won’t result in lower energy costs any more than a hammer in your shed will build a house.”

Many fixes don’t require big projects and retrofits, Daly says. “The remedy is usually adjustments and behavior changes,” he adds.

A logger that measures occupancy versus light use can reveal immediate potential for energy savings. HVAC systems can be improved when a logger reveals the imbalance of certain units working harder than others.

If an on/off logger indicates that a compressor is short-cycling, for example, there may be a leak somewhere in the line.

To address the Vermont Community Foundation’s problems, four key retrofits were presented. Kilawatt Technologies recommended new HVAC controls with a web-enabled system, an energy recovery ventilation system, building shell improvements, and use of solar photovoltaic energy. These ongoing projects and enhancements could save $215,000 over the next 15 years.

“There are probably a lot of tweaks you can make before investing in all sorts of new, fancy systems,” Lubofsky says. “You can perform all of them on a shoestring. You don’t have to break the bank or your back.”

But if you are considering a significant retrofit, data loggers can aid in that decision too.

“If you’re doing a lighting upgrade with occupancy switches, that can be pretty costly,” Lubofsky adds. “You want to be able to prove the payback and potential cost savings. Data loggers help you build the business case.”


Chris Curtland ( is assistant editor of BUILDINGS.


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Christopher Curtland