Calculating base load: The first step to a more energy efficient facility

Submitted by: Margaret McKenzie, Wednesday, May 23, 2012

Understanding the base load of a building or facility is an important first step in achieving energy efficiency.


What is Base Load?

Base load refers to energy consumption of an office, factory or house when it is not in use.   For example the base load of an office would be the amount of energy used at night after all the office workers have left for home.   For a house it would be the amount of energy used in the house after everyone has gone to sleep.  The graph below shows the base load of House Mkhize.  The base load  varies slightly, but is in the region of just over half a kWh at 3am in the morning.

Why is it Useful to Calculate Base Load?

Base loads are the first place to look for wasted energy.

In theory most factories, offices and homes should have very low base loads.  Since the facility is not in use, energy should only be required for items such as security lighting and equipment that needs to operate continuously (eg refrigerators).   However, many facilities who calculate their base load find that they are much higher than expected.  The difference between the expected base load and the actual base load is wasted energy.

In the House Mkhize example above the base load is at an expected level as a number of security lights are left on overnight along with several appliances.    However in the example from an office block below the base load is higher than expected.    Once everyone has left the office after 18:00 the base load is in the region of 20 kWh.  In the early morning it is a bit lower around 17 kWh.   The building manager has identified that the base load should be in the region of 5 kWh based on the lights and appliances that need to be left on overnight.    As a result between 12 and 15 kWh of base load is identified as wastage and the building manager can now start to investigate if lights and equipment are being left on unnecessarily or if there is an electrical fault.

It is only possible to calculate base load by regular energy monitoring.  More information on energy monitoring can be found here.

It is possible to work out a theoretical base load by identifying the lights and equipment that need to be left on after hours.   However, as illustrated in the example above expected base load and actual base load can vary considerably.


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Margaret McKenzie