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.
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.