Klein Et45

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The Klein ET45 is a small AC/DC voltage tester that needs no batteries, because it draws its power from the voltage it is measuring. If you searched for “klein et45”, you probably want to know how to use it on an outlet, what its indicator levels mean, and how it differs from the ET40 and ET60. This guide explains the ET45’s ranges, its lead holder for tamper-resistant receptacles, and the one rating detail that the sources we opened do not agree on.

Quick answer

The ET45 tests AC from 24 to 240 volts and DC from 32 to 330 volts, shown as LED levels.
It has no batteries. Klein says it is powered by the applied voltage.
Its built-in lead holder has two positions, one of which spaces the leads for tamper-resistant US outlets.
Klein lists the rating as CAT III 350V. One article we opened lists CAT III 250V, so check the marking on the tool you buy.

What the ET45 measures

Klein’s product page lists AC indicator levels at 24, 48, 120 and 240 volts. The DC levels are 32, 64, 160 and 330 volts. Each range is set by the LEDs rather than a number on a screen. The page gives the tester’s frequency range as 50 and 60 hertz for AC, which covers ordinary mains supplies in North America.

The starting level matters for interpretation. Because the lowest AC level is 24 volts, the ET45 is not a tool for checking a very low control circuit or a small battery. For those jobs, a lower-range tester such as the ET40 or a digital multimeter is a better fit. For mains outlets and fixtures, the ET45 covers the working range.

How the battery-free design works

Because the tester uses the circuit’s own voltage to light its LEDs, there is nothing to replace and nothing to run down. Klein’s page says the unit needs no batteries and is powered by the applied voltage. That is a real advantage on a job where a dead tester can give you a false negative. The trade-off is that the display only works when there is enough voltage to light it, which is why the lowest level sits at 24 volts AC.

A battery-free design also means there is no auto-off to remember. Pick it up, touch the leads, and read the LEDs. Klein lists the accuracy as typically above 90 percent of the indicated range, and above 95 percent for 24 volts AC and 32 volts DC. Those figures are the manufacturer’s, and we did not find an independent lab test to confirm them.

Using the lead holder for tamper-resistant outlets

Many newer US receptacles have tamper-resistant shutters that block a straight probe from entering only one slot. The ET45 has a built-in lead holder on its back. Klein describes two positions for the holder. One position spaces the leads so they can enter a tamper-resistant outlet. The other stores the leads when the tester is not in use. The leads dock into the holder for storage, which keeps them from tangling in a bag.

Klein’s page notes that the leads are not interchangeable, so keep the two leads matched to their own positions in the holder rather than swapping them. The product page does not describe any other care steps for the leads.

How to read a check on an outlet

Start with a known live source to confirm the tester responds. Then place the leads in the outlet slots, using the spacing position of the holder if the receptacle is tamper-resistant. Watch which LED levels light. A standard 120-volt receptacle should light the 120-volt level. If only the 24-volt level lights, or nothing lights, do not assume the circuit is dead. Check the connection, try another outlet on the same circuit, and confirm the tester on a live source again.

Klein’s press material for its residential testers describes the use of the ET45 for testing tamper-resistant US-style outlets. That is the main job the product is designed for. For a broader background on outlet checks, see how to use a multimeter on an outlet.

The rating question

This is where the sources differ. Klein’s product page and its residential press release both list the safety rating as CAT III 350V, with Class 2 and double insulation, and pollution degree 2. A CEPRO article we opened describes the ET45 as CAT III 250V, Class 2, double insulation. The two statements conflict, and we cannot resolve the conflict from the pages we opened.

The practical advice is simple. Check the marking printed on the tool you receive, and use the rating that matches the marking and the circuit you are working on. Do not assume a higher rating is a reason to work on a higher-voltage system without the training and tools that the job requires. A CAT rating describes the environment the tool is designed for. It does not make dangerous work safe. For a general explanation of how these ratings work, see what a CAT rating means on a multimeter.

Ingress, drop and build

Klein lists the ingress protection as IP44, which means dust and water resistant to a limited degree. The page gives a drop protection height of 9.8 feet, or 3 meters. The listed dimensions are 4.45 inches long, 1.19 inches high and 1.05 inches wide, with a weight of 1.8 ounces, or 51 grams. The compact body suits a pocket or a small tool bag. Keep it dry and inspect the leads for wear before each use.

What the ET45 does not do

The ET45 does not test continuity. Klein’s page lists no continuity function. It also does not give a numeric voltage reading, so it cannot replace a multimeter for measured values, resistance or current. Use it as a fast voltage check and pair it with a multimeter for diagnosis.

Klein’s listing shows the tester alone as the included item. The page does not list a case or spare leads.

How we chose

This article covers only the Klein ET45. We began with Klein’s product page, which gives the most complete set of ranges, the frequency range, the ingress rating and the dimensions. We then opened the CEPRO article to compare the rating and the battery-free statement, and Klein’s residential press release for the use-case wording. We did not use marketplace reviews, since our aim here is to explain the tester’s ranges and limits.

What we could not verify

The safety rating conflict. Klein lists CAT III 350V and CEPRO lists CAT III 250V. We have reported both and did not pick one.
We did not find an independent lab test of the accuracy figures. The accuracy statement is Klein’s.
The sources we opened do not give a current retail price, and we do not state one here.
The sources do not say whether the ET45 is discontinued. The Klein product page shows a buy button and no discontinued notice.
We could not confirm how the tester performs on very low-voltage control circuits, because the lowest AC level is 24 volts.

FAQ

Does the klein et45 need batteries?

No. Klein says it is powered by the voltage it is testing.

What voltage range does it cover?

Klein lists AC from 24 to 240 volts and DC from 32 to 330 volts, shown as LED levels.

Can it test tamper-resistant outlets?

Yes. The lead holder has a position that spaces the leads for tamper-resistant US-style outlets.

Does the ET45 test continuity?

No. Klein’s listing shows no continuity function.

What is the correct CAT rating?

Klein lists CAT III 350V, while one article we opened lists CAT III 250V. Check the marking on your tool.

How is it different from the ET40?

The ET45 has no batteries and a higher DC range, while the ET40 uses two AAA batteries, has a lower AC starting level of 12 volts and includes an auto-off feature.

Bottom line

The Klein ET45 is a battery-free voltage check for mains outlets and fixtures, with a lead holder built for tamper-resistant receptacles. Confirm it on a live source, read the LEDs as approximate levels, and resolve the CAT rating from the marking on your own tool before you rely on it.

Sources

Klein Tools, AC/DC Voltage Tester ET45: https://www.kleintools.com/product/ET45 (opened 2026-10-29)
CEPRO, Klein Tools AC/DC Voltage Testers Validate Residential Wiring: https://www.cepro.com/news/klein_tools_ac_dc_voltage_testers/7848/ (opened 2026-10-29)
Klein Tools press release, AC/DC voltage testers for residential wiring: https://www.kleintools.com/content/klein-tools-introduces-easy-use-acdc-voltage-testers-residential-wiring (opened 2026-10-29)