What size transformer do I need for a video doorbell?

Two numbers on the label, and which one usually fails#

A doorbell transformer's label gives two figures. Volts is the pressure on the doorbell wires, and VA (volt-amperes) is how much power the transformer can deliver at that voltage. Divide VA by volts and you get the current it can supply: a 16 V, 10 VA unit gives about 0.63 A, a 16 V, 30 VA unit about 1.9 A.

Two answers circulate about which matters. One says the camera needs 30 VA, so upgrade. The other says the 16 V, 10 VA transformer behind most chimes is fine. Both come from real manufacturer pages:

• The 10 VA answer is right for most brands. Ring's Pro and Plus models, every Google Nest doorbell, Arlo's Essential Wired and Tapo's hardwired models publish 10 VA as the minimum.
• The 30 VA answer is eufy's. Its support page states: "The eufy wired doorbell requires 16-24VAC, 30VA or above." Among the six brands read for this page, it is the only one asking for more than 10 VA.

What catches more people is voltage, because a low-voltage transformer fails on volts before VA comes into it. Ring's Pro and Plus, every wired Nest, Arlo and eufy all start at 16 V. Transformers rated 8 V and 10 V are still sold (Edwards lists both in its catalog), and a doorbell that needs 16 V gets nothing useful from them.

The requirements, brand by brand#

As each maker publishes them, read in October 2026. "None stated" means the page read gives no maximum, not that any size is approved.

Ring and Google both give 50/60 Hz, which is ordinary US household AC. Google adds a looser range for the original wired Nest outside North America (12 to 24 V, 8 to 40 VA); in the US the North American figures apply.

Your transformer against every doorbell#

The other half of the question is what is already in your wall. These are real catalog ratings from Edwards' 590 series of Class 2 doorbell transformers, all with a 120 V primary, checked against the table above. Several models have more than one output (tap), each with its own rating.

"At the line" for Tapo is literal: TP-Link recommends "over 10VA", and a 10 VA transformer is exactly 10.

Three things fall out of the table that no single maker's page tells you:

1. The 16 V, 10 VA transformer that Edwards sells for "standard doorbells and chimes" meets the published minimum of every brand except eufy. It meets Ring's Pro and Nest's wired models exactly at their floor, with nothing to spare.
2. There is a band that fits everyone: 16 to 24 V at 30 to 40 VA. eufy's floor is 30 VA, and Ring, Nest and Blink's ceiling is 40 VA. Edwards describes the 598 and 599 as transformers for "long wire runs or for applications requiring greater power".
3. Do not oversize past 40 VA for Ring, Nest or Blink. Their pages give 40 VA as the top of the range, not a suggestion, so a heavier transformer bought "for headroom" is outside the published requirement.

Why a doorbell that meets the minimum can still be short of power#

The figures above are for the transformer. The doorbell shares that supply with the chime and the wiring, and each maker handles that differently. Each of these is a manufacturer instruction, not an optional extra:

• Ring Wired Doorbell Plus and Pro need the Pro Power Kit. Ring says "You must use the Pro Power Kit with your Wired Doorbell Plus and Pro to make sure that they receive the right amount of power to work correctly." It goes inside the chime housing. If you bypass the chime instead, Ring has you set the Doorbell Type to "None" or "No Chime" in the app. Ring's guidelines also say only the original Video Doorbell (1st gen) and Video Doorbell 2 need a diode with a digital chime.
• Wired Nest doorbells need the chime connector from the box. Google says the wired 1st, 2nd and 3rd gen "must be installed with the chime connector included in the box." Google also says intercom and gate systems "typically don't work with the Nest doorbell", and chimes that run only on batteries do not work with Nest doorbells either.
• Tapo's Always-On mode needs the chime bypassed. TP-Link says that to enable it, "you must first bypass your existing chime by inserting a jumper wire", and lists an existing chime "not properly bypassed" as a cause of insufficient power.
• Blink still needs its batteries when wired. Blink says the Video Doorbell "requires Energizer AA 1.5-volt lithium non-rechargeable batteries for operation, even when wired." The wiring powers the chime feature; it does not replace the cells.

If you are adding a Matter controller or a hub to the doorbell afterwards, none of this changes. Power is settled at the wall, and cameras and doorbells covers what the video side of the standard does and does not carry.

How to find out what you have#

1. Find the transformer

   Google and Blink give the same short list of places to look: near the main electrical panel, inside the chime box, in the garage or in the attic. eufy adds the basement. Following the thin wire from the chime usually gets you there.

2. Read the nameplate

   The label gives the output volts and VA. Blink notes the VA may be printed as "max load" or "max power consumption", and the label may be a sticker, molded into the housing, or inside it.

3. Measure the voltage if the label is gone

   Arlo's guide says "You can use a voltmeter to check the voltage." Set the meter to AC volts and measure across the transformer's low-voltage terminals. A meter reads volts, not VA, so a measurement cannot tell you whether a 16 V transformer is a 10 VA or a 30 VA one. Only the label does.

4. Compare against both tables

   Find your doorbell in the first table and your transformer's rating in the second. If it fails on volts, VA will not rescue it. If it passes at the minimum, expect no margin.

Replacing the transformer#

Doorbell transformers usually sit where the 120 V side is wired into a junction box or panel, which is why Google says "If the system doesn't meet the power and voltage requirements, or if you're not sure, contact a local certified electrician," and eufy says to hire a licensed electrician "If you're not comfortable handling the wiring". eufy's own procedure starts with turning off the main power and confirming it is off.

On the low-voltage side, eufy notes that because the output is alternating current, "it doesn't matter which wire connects to which terminal." Edwards' 590 series mounts through a standard 1/2 in knockout or on surface feet, and suits plastic or metal boxes, so a like-for-like swap rarely means new holes. If the junction box is already crowded, work through the box-fill count in smart switch box depth and fill before adding splices.

The 24 V AC transformer in your furnace or air handler is a different circuit: it powers the heating controls through the R and C terminals described in the thermostat C-wire section. None of the doorbell makers read here name it as a power source, so this page does not treat it as one.

If you rent, ask before you start: wired doorbells are one of the few categories a smart home for renters treats as a modification to the unit. If you are moving out of a house you own, a wired doorbell usually conveys with it, as moving house explains.

Picking a doorbell around the transformer you have#

If you would rather not touch the transformer at all, the tables reverse into a buying rule:

• 16 V, 10 VA (the usual chime transformer): Ring Pro, Plus, 2K Plus and 4K Pro, any wired Nest, Arlo Essential Wired and Blink all list it as within range. Ring's battery models and Ring Wired have the most margin, because their floors are 5 and 8 VA. eufy's wired doorbells do not.
• 8 V or 10 V: only models with an 8 V floor accept the voltage (Ring battery models and Elite, Nest Doorbell (battery), Blink and Tapo), plus Ring Wired at 10 V. Each still needs its own minimum VA, so a 10 V, 5 VA unit suits only Ring's battery models and Elite.
• 16 or 24 V at 30 VA or more, up to 40: anything in the first table.
• No wiring at all: a battery doorbell, with the recharges and the delay before the stream starts that cameras and doorbells describes.

Power is only the first filter. Whether the doorbell records anything when the internet drops is a separate question, answered in what still works in an internet outage and checkable for your own setup with the outage audit, and who sees the footage is covered in smart home privacy. Cameras also carry the highest risk of a vendor shutting the service down, which is worth weighing before the transformer work. Doorbells are Wi-Fi devices because video needs the bandwidth, so the network a smart home wants applies to the front door as much as to anything inside. And Matter cameras explains why no product has certified as a Matter video doorbell yet.

Where this page stops#

• US, 120 V primary transformers. The volts and VA figures are North American where a maker splits them by region.
• Brands read: Ring, Google Nest, Blink, Arlo (Essential Wired only), eufy and Tapo, from their own support pages and guides, as of October 2026. Other Arlo models, Wyze, ecobee and Aqara were not read, so the page makes no claim about them.
• Transformers read: the Edwards 590 series. Other makers' units with the same output rating meet the same rows, but the model numbers here are Edwards'.
• Intercoms, gate systems and DC supplies are outside this page. Google says intercom and gate systems typically do not work with Nest doorbells.
• No manufacturer here publishes how much of the transformer's VA a chime uses, so the page does not estimate what is left for the camera when both share a 10 VA unit.