Does Outdoor Temperature Impact Energy Management System (EMS) Payback?

(Part 4 of 5)

Energy management systems are an investment but they pay for themselves, typically within 2 – 4 years. EMS providers can calculate your project payback based on specific data.

We’ve already talked about  natural gas rateselectricity rates and unitary room controls with central controls.

This week we continue the discussion with temperature and “number of degree days”.

Temperature and the “Degree Days” Concept

Certainly your property’s outside annual temperature affects HVAC energy savings, thereby affecting project payback in the short term and utility costs in the long term. When the occupant feels comfortable enough with their surrounding temperature, there’s no need to “turn on the HVAC”.  Most of us are comfortable with indoor temperature ranging from the mid-sixties up to the low-seventies Fahrenheit.

When the occupants feel colder or hotter, they turn to their traditional thermostats and “crank it up or down”.  And the longer they continue to feel less-than-comfortable (both day and night), the longer they’ll keep their HVAC turned up or down, compared to the time when they did feel comfortable.  So, the higher or lower the temperature from when they were comfortable—and the longer they run their HVAC—results in the total amount of heating or cooling degree days used. It’s a simple concept – but very important to EMS payback.

65°has been widely accepted as a temperature people are comfortable without needing HVAC whatsoever.  

If the temperature is 65°F all day and night all year round, based on this definition of “degree days” they will need zero degree days of HVAC—forever. There is no energy savings possible, because their HVAC is not using any energy to begin with. 

But if their HVAC is lowered to 55°F in the summer and remains there all day long, then they had a 10 cooling degree day; their air conditioner is running all day. 

If their HVAC is raised to 75°F in the winter and remains there all day long, then they had a 10 heating degree day; their furnace is running all day long.

Bottom Line:

By reducing your heating and/or cooling degree days – such as not running the HVAC at all when you are not in the room – you are reducing your HVAC energy costs in direct proportion to the total amount of heating and cooling degrees days you don’t use.  The fewer degree days you use, the quicker the project payback, and the greater the stream of monetary savings long term.

Contact a Telkonet representative to learn more about how much an EMS can save YOU. sales@ or 888-703-9398.

And visit us next week when we continue our discussion of ROI on Energy Management Systems, and specifically about unitary PTACs versus central FCU’s, and occupancy-based energy management.