What Is an Electronic Load? Modes, Uses and How It Works

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What is an electronic load? It is a programmable test instrument that draws current from a DC source so you can see how that source behaves under load. Power supplies, batteries, and solar panels respond differently when loaded, and an electronic load lets you set the load on purpose and measure the result. Most units offer four modes: constant current, constant voltage, constant resistance and constant power.

What an electronic load does

Keysight describes electronic loads as test instruments that mimic real-world loads to test the performance of power devices such as power supplies and batteries. Tektronix describes the same idea in simpler terms: the instrument sinks power, using transistors to simulate an ohmic resistance when it tests DC voltage and current sources.

The key difference from a passive resistor is control. A resistor draws current that rises and falls with the voltage applied across it. An electronic load actively regulates what it draws. Keysight’s product page says a DC electronic load draws current and absorbs power from a DC source, and that unlike a passive resistor, it actively controls how much current, voltage, resistance, or power it draws from the device under test.

Because the load is controlled, the same unit can run a repeatable test. You can set a current, run the test, change one value, and run it again. That repeatability is the main reason engineers use one in place of a bank of fixed resistors.

The four operating modes

Most electronic loads offer four modes. Each one defines the quantity the instrument holds steady while the source voltage or current changes.

Constant current (CC)

In CC mode the load maintains a constant current regardless of changes in the input voltage. Keysight’s glossary says this mode is used to test batteries, fuel cells, and solar panels. Tektronix explains the control action: the load adjusts its effective resistance to hold the input current steady. Internally, a current amplifier compares the voltage across a current shunt with a reference and adjusts how hard the load transistor is driven.

CC is the mode most people start with. It suits power supply testing, battery discharge tests, and LED driver checks, where a stable current draw is the point of the test. Keysight notes a trade-off: a CC load may not suit sources whose output voltage varies a lot, because the load keeps current constant even as the source voltage moves.

Constant voltage (CV)

In CV mode the load holds the input voltage at a set level by adjusting the current it draws. Keysight’s product page says this suits battery charging simulations and voltage regulation tests. Tektronix notes that CV is less straightforward when the source has limited capacity, because the load keeps pulling current until the source voltage falls to the set point.

Keysight’s glossary lists CV for testing power supplies and uninterruptible power supplies (UPS). If a source must hold its voltage under a changing load, CV mode is the natural choice.

Constant resistance (CR)

In CR mode the load behaves like a fixed resistor. The current it sinks changes with the applied voltage, following Ohm’s law at the set resistance. Keysight’s glossary cites LED drivers, motor controllers, and DC-DC converters as examples. The product page notes that CR suits resistive loads such as heaters.

CR is the mode that most closely matches how a simple resistive load behaves, which makes it useful for checking how a source responds to a load that changes with voltage.

Constant power (CP)

In CP mode the load keeps power steady by changing the current as the voltage changes, using P = V x I. Keysight’s glossary lists battery chargers, AC adapters, and automotive power management as uses. Keysight’s product page adds DC-DC converter, solar panel, and battery performance testing.

CP is useful when a device is designed to deliver a fixed power level. A solar panel’s output, for example, changes with irradiance and temperature, and CP mode lets you see how the panel and its charge controller respond at a set power draw.

Which mode runs first

When several modes could apply at once, the instrument has to pick one. Tektronix states the priority order: CP has the highest priority, followed by CC, CR, and CV. Practical consequences follow from that order, so read your model’s manual before you assume that a setting you chose is the one in effect.

Where electronic loads are used

Keysight’s glossary and Tektronix’s FAQ both point to the same core group of uses. Engineers test batteries, power supplies, solar panels, UPS units, automotive and industrial supplies, and consumer power adapters. The Tektronix FAQ also lists capacitors and turbines as DC sources that a load can test.

For batteries, a constant current discharge is a common method. Keysight’s product page describes it as a way to draw a set current from a battery to measure its usable energy. The same logic applies to a power supply: hold a current, then check whether the output voltage stays inside its specification.

Protection matters during these tests. Keysight’s glossary notes that electronic loads include overvoltage and overcurrent protection to keep the load and the source safe during testing. Protection features differ between models, so check the specification for the limits your test needs.

Regenerative and non-regenerative loads

Tektronix points out that some loads are regenerative. Its FAQ cites EA’s ELR 10000 Series, which returns more than 90 percent of the sunk energy to the utility. A non-regenerative load turns that energy into heat. For a short bench test, the difference may not matter. For long discharge tests or high-power work, it changes the heat load on your bench and your power bill.

What to check before you buy or use one

Start with the power and voltage range. Make sure the load can accept the full output of the source you plan to test, including its maximum voltage and current. A load rated below the source’s output will not run the test you want.

Next, check which modes the unit offers. If you need CR for a resistive simulation and CP for a converter test, confirm that both are available on the model you are considering.

Look at the accuracy and resolution for the quantity you measure most. In CC operation, Tektronix notes that only the error of the current is effective, which is useful to know when you read a datasheet. Read the accuracy line for each mode you plan to use.

Finally, check the safety features and the connection method. Confirm that the unit has overvoltage and overcurrent protection, and check whether it sinks power or returns it to the grid.

What we could not verify

We did not find a single source that gives a typical price range, a standard for transient response, or a standard set of connector types across manufacturers, so this guide does not state them. Keysight’s knowledge center article on how an electronic load regulates input voltage, current, and resistance returned an could not be retrieved, so we did not use it. Specific model ranges, accuracy figures, and protection limits must come from the manufacturer’s datasheet for the exact unit.

Summary

An electronic load is a controlled sink for DC sources. It draws current or power in a set mode so that you can measure how a battery, power supply, solar panel, or converter responds. The four modes, CC, CV, CR, and CP, each hold a different quantity steady. Check the power range, the available modes, the accuracy line for each mode, and the protection features before you rely on a unit for a test.

Quick answer

An electronic load sinks power from a DC source in a controlled way. It can hold current, voltage, resistance or power steady while you measure how the source responds. Check the power range, the available modes and the accuracy line for each mode before you buy.

How we chose these sources

We used manufacturer and test-equipment vendor explainers that describe the instrument and its modes in plain language. We opened each page directly and used only what it states. Where a page did not give a figure, this guide leaves it out.

FAQ

Is an electronic load the same as a resistor?

No. A resistor draws current that rises and falls with the applied voltage. An electronic load actively controls what it draws, so it can hold current or power constant as the source changes.

What is the most common mode to start with?

Constant current is the mode most people start with. Keysight’s glossary says it is used to test batteries, fuel cells and solar panels.

Which mode has priority when several could apply?

Tektronix states the order as constant power first, then constant current, constant resistance and constant voltage. Check your model’s manual to confirm how it behaves.

Can an electronic load return energy to the grid?

Some can. Tektronix cites regenerative models that return energy to the utility, while non-regenerative loads turn it into heat. Check the datasheet for the model you are considering.

Sources

• Keysight Oscilloscope Glossary: What are Electronic Loads? (opened 2026-10-28)
• Keysight: DC Electronic Loads (opened 2026-10-28)
• Tektronix: What Is an Electronic Load (E-load)? Fundamentals and FAQs (opened 2026-10-28)

Related guides

For DC voltage work with a meter, see our guide to multimeters for DC voltage, and our guide to battery voltage meters.