Rank #6 in Best UPS Battery Backup 2026: 9 Ranked, and Why 2200VA Isn't 2200W
Eaton 3S Gen2 550VA / 330W (3S550B)
- Rating
- 4.2
- Ratings
- 80
- Rank
- #6
Price and rating as shown on Amazon when we collected them. Both change.
The Eaton 3S Gen2 3S550B is the smallest unit in our best UPS battery backup guide, at number 6 of nine, and it is the cheapest of the group at £55.84. It carries 4.2 out of 5 from 80 Amazon ratings. Eaton sells it as a 550 VA UPS and the spec table rates the output at 330 watts, a factor of 1.67 between the number on the front of the box and the number that decides what you can actually plug in. Six BS outlets are fitted: three with battery backup and three surge only, with a quoted standard runtime of 10 minutes.
Some fields in the listing do not describe this device well. Form Factor is given as "ATX", a PC case standard rather than a UPS category. Battery Average Life reads "10 minutes", the same figure Eaton quotes for runtime. Amperage and Output Current both read 10 Amps; at the listed 230 volts that works out at 2300 VA, roughly four times the 550 VA in the product name. The lower temperature rating is also listed as 40 degrees Celsius, which is a warm figure to call a lower limit. Everything on this page comes from the Amazon listing for this product, not from testing we have carried out.
How those 80 ratings break down
An average hides its own shape. This is the spread behind the 4.2 stars.
Specification
Exactly as published on the Amazon listing, field for field.
| Price | £55.84 |
|---|---|
| Amazon rating | 4.2 out of 5, from 80 ratings |
| Listed capacity | 550 VA |
| Rated output | 330 W |
| Outlets | 6 BS sockets - 3 battery backup, 3 surge only |
| Stated runtime | 10 minutes |
| Battery cell type | Sealed lead acid |
| Form factor (as listed) | ATX |
| Amperage (as listed) | 10 Amps |
What buyers actually say
Quoted from customer reviews on Amazon
Verified purchase“Product is a good size, not taking up too much space. You can see the size of it sat next to my rack.I have mine connected to a Raspberry Pi via USB, reporting into Home Assistant using the NUT integration so that I can monitoring Load, Battery charge, status etc.I can't comment on performance yet, only that I have it at 48% load and have switched off the power a couple of times and everything works as expected, reporting an updated status to NUT in a matter of seconds.”
Verified purchase“I work remotely and while getting our kitchen fitted, had a bit of pain working off slow mobile data while the electrician had sockets off for hours. Decided to invest in two of these. One is attached to the main deco node and fibre ont box. The other is upstairs attached to the 2nd deco node which has an ethernet feed to my dock/laptop. (Aware now I could have had a mini ups for this, but the extra sockets are useful for the future). My extension for my standing desk, dock, laptop and monitors is plugged into an Anker solix c1000. Today the electrian was fault finding our new hob which kept tripping. He was cutting the power while testing over an hour or so. The devices worked flawlessly and I was able to continue working. The devices make a beep while on backup so you are aware. Happy with my purchase.”
What it is up against
The rivals it was ranked against in Best UPS Battery Backup 2026: 9 Ranked, and Why 2200VA Isn't 2200W.
Questions people ask
Does the Eaton 3S Gen2 3S550B really deliver 550 watts?
No. Eaton lists the 3S550B as 550 VA but rates the output at 330 watts in the spec table, so the VA figure is about 1.7 times the usable watt figure.
How many sockets does the Eaton 3S550B have, and are they all backed by the battery?
Six BS outlets in total. Three provide battery backup and surge protection, and three are surge only, so only half the sockets keep running in a power cut.
How long will the Eaton 3S Gen2 keep my equipment running?
The listing quotes a standard runtime of 10 minutes. It does not say at what load that figure is measured, so treat it as a best case rather than a promise for whatever you connect.
What does Eaton say the 3S550B is suitable for?
The listing names desktop computers, wireless networks, internet routers, printers and gaming consoles, along with "other electronics".
Can the Eaton 3S Gen2 be monitored from a computer?
The listing states the USB port is HID-compliant and integrates automatically with most common operating systems, so no separate driver is needed for basic reporting.
What comes in the box and what warranty applies to the Eaton 3S550B?
Eaton lists the UPS itself, 2 IEC output cords at 1.5m, a quick start guide and safety instructions, with a 2 year standard warranty.
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