The PSU brand ranking

Corsair is the best PSU brand for most UK buyers, and the Corsair RM850e (2025) at £89.99 on Amazon UK at the time of writing (October 2026) is the unit to buy. It is the cheapest of the seven 850 W units ranked here, with a 7-year warranty. The be quiet! Pure Power 13 M 850W and Cooler Master MWE Gold 850 V3 cost £20.00 and £27.41 more and extend cover to 10 years. Wattage planning comes first, and How many watts PSU do I need? sets out the sums.

How do you rank the best PSU brands?

By what can be checked: warranty length, price per watt, connector standard and the maker's specification sheet. No maker or UK retailer publishes failure rates, so this ranking makes no reliability claim beyond what a warranty implies. Every unit compared is rated 850 W, which keeps the price comparison fair, and the ranking weighs four points:

• Warranty. A 10-year warranty puts a decade of repair cost on the maker. Seven years is a solid mid-range floor.
• Standard. ATX 3.1 with a native 12V-2x6 connector suits current graphics cards. The Seasonic CORE V2 GX-850 is also an ATX 3.1 unit.
• Price per watt. The 850 W band runs from 10.6p to 19.9p per watt here.
• Noise. Semi-passive fans stop at low load. Corsair, be quiet! and Cooler Master all list a zero-RPM or semi-passive mode.

Builders pairing a unit with a card should check Best graphics card UK 2026 for power figures, and old-PC upgraders can use How to upgrade an old gaming PC in 2026.

1. Corsair RM850e (2025) - best overall

The RM850e (2025) wins because nothing at 850 W costs less and nothing important is missing. Corsair gives it ATX 3.1, a zero-RPM mode and a 140 mm case length that fits compact cases. Corsair covers it for 7 years, three fewer than the be quiet! and Cooler Master alternatives.

2. be quiet! Pure Power 13 M 850W - best for noise and warranty

The be quiet! Pure Power 13 M 850W costs £20.00 more than the Corsair RM850e (2025) and buys three extra warranty years, a semi-passive 120 mm fan and a Cybenetics Platinum efficiency rating. be quiet! has built its name on low noise, which suits a small desk or a quiet room. The Pure Power 13 M also comes in a 1,000 W version for larger systems.

3. Cooler Master MWE Gold 850 V3 - best 10-year value

The Cooler Master MWE Gold 850 V3 sits £27.41 above the Corsair RM850e (2025) and £7.41 above the be quiet! Pure Power 13 M 850W. It pairs a 10-year warranty with a 90-degree 12V-2x6 connector, which keeps the cable tidy behind a graphics card. At 160 mm it is 20 mm longer than the Corsair, which matters in small cases.

4. Seasonic CORE V2 GX-850 - for buyers who want the brand

The Seasonic CORE V2 GX-850 lists the same 850 W rating and 7-year warranty as the Corsair RM850e (2025) for £29.00 more, with ATX 3.1 on both. It is a fair unit at an uncompetitive price, which places Seasonic fourth.

Where do Gigabyte, MSI and Thermaltake rank?

Gigabyte ranks fifth, MSI sixth and Thermaltake seventh, on Amazon UK prices in October 2026. Each is a sound unit priced above its rivals or short of their cover.

• Gigabyte. The Gigabyte AORUS Elite P850W is 80 Plus Platinum and ATX 3.1 with a 10-year warranty, 8 SATA connectors and a 140 mm body, at £119.99. It costs £30.00 more than the Corsair for the Platinum label.
• MSI. The MSI MAG A850GLS PCIE5 is ATX 3.1 with native 12V-2x6, a 135 mm fan and 8 SATA connectors for £99.99. MSI advertises a 10-year warranty, though some retailers list 7 years, so buyers should confirm cover at purchase.
• Thermaltake. The Thermaltake Toughpower GT 850W lists ATX 3.1, 80 Plus Gold, a Smart Zero fan and a 5-year warranty at £169.48, £79.49 above the Corsair for half the cover of a 10-year unit.

Best PSU brands: 850 W spec sheet

What does the extra money buy in a PSU?

Beyond £89.99, the extra money buys years of warranty, not watts. Compare Electronic divided each Amazon UK price by 850 W and by the warranty years to rank seven units.

The Corsair RM850e (2025) costs 10.6p per watt, the Thermaltake Toughpower GT 850W 19.9p, almost twice as much. Per warranty year the be quiet! Pure Power 13 M 850W works out at £11.00 against £12.86 for the Corsair, so the be quiet! is cheaper to own across its cover despite costing £20.00 more on the day. Buyers who keep a PC for three years or less will not use the extra seven years, and should take the Corsair.

What do ATX 3.1 and 12V-2x6 change when choosing a PSU brand?

They decide whether a modern graphics card plugs in without an adapter. ATX 3.1 is the current power supply standard, and 12V-2x6 is the 16-pin connector that carries up to 600 W to a graphics card. Cooler Master lists a single 12V-2x6 connector on a 600 mm cable for the MWE Gold 850 V3, and be quiet! lists 12V-2x6 on the Pure Power 13 M 850W. The Seasonic CORE V2 GX-850 lists ATX 3.1 and PCIe 5.1 ready on Amazon UK, which suits a card with a 12VHPWR socket.

Five of the six units priced under £120 here list ATX 3.1, so the standard no longer separates the budget from the premium. Warranty, noise and price do. Buyers sizing a unit for a specific card should start with How many watts PSU do I need?

How to choose a PSU brand, and who should skip a pick

Choose by system life: a 3-year build takes the cheapest 850 W unit, and a 7-year build takes 10 years of cover. Three profiles cover most buyers:

• Buyers building a gaming PC with a mid-range graphics card take the Corsair RM850e (2025) and spend the £20.00 saved on storage; see Best NVMe SSD for gaming UK 2026.
• Buyers in a quiet room or a long-term build take the be quiet! Pure Power 13 M 850W or the Cooler Master MWE Gold 850 V3 for 10 years of cover.
• Buyers paying for a Platinum label or a Thermaltake badge should skip them. The Gigabyte costs £30.00 and the Thermaltake £79.49 more than the Corsair, and neither adds watts.

Verdict

Corsair leads on price, with the Corsair RM850e (2025) at £89.99. be quiet! and Cooler Master lead on cover, with the be quiet! Pure Power 13 M 850W at £109.99 and the Cooler Master MWE Gold 850 V3 at £117.40. Wattage choice comes first, and How many watts PSU do I need? settles it. Upgrade projects are covered in How to upgrade an old gaming PC in 2026.