Where Do Energy Losses Go in an Electrical System?

• Generation
• Transmission
• Distribution and use
• Waste heat

What you will learn

• Say where lost energy usually goes.
• Name the three stages of an electrical system where losses occur.
• Distinguish reducing losses from making energy disappear.

Before you start

No prior knowledge is needed. The article uses United States figures as the example and gives only the numbers the sources contain.

Where does energy that does not become usable electricity go?

Energy does not vanish; it turns into another form. According to the University of Illinois notes on energy principles, if released energy is not used, it escapes and is usually "wasted" as heat.

The first law of thermodynamics says the total amount of energy is constant, so the amount lost as waste heat can be determined. In the real processes described by the Illinois notes, some energy becomes less usable. Waste heat remains energy, but it is not the electricity the system aims to deliver.

• Energy put in
• Useful part
• Part that becomes heat

At which stages do losses occur?

At three: generation, transmission and distribution. The U.S. Energy Information Administration (EIA) defines electrical system energy losses as the energy lost during generation, transmission and distribution of electricity, including plant and unaccounted-for use, according to the EIA glossary.

For transmission and distribution alone, EIA estimates that losses averaged about 5% of the electricity transmitted and distributed in the United States from 2018 through 2022, according to the EIA FAQ page. That figure does not include losses at generation.

• Generation
• Transmission
• Distribution

What does reducing losses mean?

Reducing losses means making the energy that does not reach the desired output smaller. Efficiency needs a stated input, useful output and system boundary. Transmission losses differ from whole-system losses because they cover different stages.

• Energy put in
• Useful part and loss

Real-world example

Think of carrying a bucket with a small hole from the well to your house. Water drains away along the way even if you walk carefully. The water left in the bucket and the water that escaped still make up the original amount. An electrical system likewise needs to account for both delivered electricity and energy converted to heat.

This is only a comparison to help you remember. Electricity is lost as heat, not by leaking like water.

Common misunderstandings

The figure of about 5% is not the whole loss of the electrical system. It covers only transmission and distribution in the United States over the years given.

Lost energy is not energy that disappears. It goes into heat.

Losses are not only in the wires. EIA's definition includes generation.

Frequently asked questions

Where does lost electrical energy go?

Mostly into heat, according to the University of Illinois notes.

How large are transmission and distribution losses?

EIA estimates about 5% on average in the United States from 2018 through 2022.

Does reducing losses violate energy conservation?

No. Reducing losses changes how energy is divided between the useful output and the remainder.

Summary

• Lost energy usually escapes as heat.
• Losses occur in generation, transmission and distribution; the last two together are about 5% in the United States.
• Assessing losses requires a stated input, useful output and set of stages.