Discussing Various Energy Saving Rates

As the name suggests, the energy saving rate is the percentage of electrical energy saved. However, the precise definition requires further discussion; below we describe the definitions and characteristics of various energy saving rates.

1. Percentage of energy saving before and after adopting energy-saving devices

CECS163-2004 "Technical Specification for Application of Power-Saving Devices in Buildings" is an older group standard that provides two calculation methods for energy-saving rate.

Method 1: Power Consumption Measurement Method:

Under consistent load and operating conditions, measure the electricity consumption in energy-saving mode and non-energy-saving mode over the same time period. The energy saving rate is calculated according to Formula 1:

where r is the energy saving rate;

A0—Energy consumption without energy-saving devices, kW·h;

A1—Energy consumption when connected to a power-saving device, kW·h.

Method 2, Power Measurement Method:

With constant load and operating conditions, measure the active power of the system with and without the energy-saving device connected. The energy saving rate is calculated according to Formula 2:

In the formula, P0 is the active power value when no energy-saving device is connected, in kW;

P1 — Active power value when connected to an energy-saving device, kW.

Therefore, this power saving rate is essentially the power saving rate of the power-saving device or energy-saving device.

2. Percentage of energy saving before and after adopting energy-saving products

This energy-saving method does not require separate power-saving devices (as mentioned above). The electrical product itself is an energy-saving product, and energy savings are evaluated by comparing performance before and after its use.

JGJ/T 307-2013 "Standard for Energy Saving Evaluation of Urban Lighting" defines the electricity saving rate, which is the percentage of electricity saved by adopting energy-saving measures compared to the electricity consumption without such measures.

The energy-saving measures defined herein include the adoption of energy-saving devices, energy-saving products, energy-saving controls, and energy-saving designs, and are not limited to the use of energy-saving devices, making the scope broader than that of CECS163.

3. Energy saving percentage based on the reference value

Taking lighting as an example. GB/T 51268-2017 "Green lighting inspection and evaluation standard" defines the lighting energy saving rate, which is the percentage reduction in actual lighting power consumption compared to the baseline value achieved through optimized design and reasonable operation.

Current lighting conditions are favorable. For example, LPD values have long had standard values, including current and target values, which have been used for many years. This has accumulated experience, making the lighting industry quite familiar with them and easier to promote.

Therefore, although there is no authoritative unified standard definition for the energy saving rate, with multiple definitions and calculation methods, it plays a positive role in energy saving. It is also hoped that a unified definition will be established in the future to measure energy saving performance with a consistent standard, avoiding inconsistent interpretations and ensuring that discussions on energy saving and electricity saving are on the same page.