Power Supply Wattage: How to Work Out How Many Watts Your Computer Needs, and Why the Number Isn't Everything

The power supply is the component people think about last. It's often where they save money: "what does it matter, as long as it switches on". But the power supply feeds every other part, and its capacity and quality determine stability, component lifespan and even safety. Let's look at how to choose the right power supply wattage and why the "watts" figure on the box is far from the only important parameter.

What uses power in a computer

The main consumers are the graphics card and the processor. Everything else — the motherboard, memory, drives, fans and USB devices — usually accounts for 50–100 W. So the calculation starts with the graphics card and processor.

• An office computer with no graphics card — draws 60–150 W; a quality 400–450 W unit is enough.
• A mid-range gaming computer — 300–450 W under load; 550–650 W is sensible.
• A powerful gaming or work computer — 500–700 W; it needs a 750–850 W unit.
• Top-end configurations — 1000 W or more.

Graphics card peak loads

For fractions of a second, modern graphics cards can draw considerably more than their rated power. A weak or poor-quality power supply treats such a spike as an overload and its protection kicks in — the computer switches off or restarts instantly in a game. That's why graphics card makers recommend units with plenty of headroom, and those recommendations are worth following.

Why headroom matters

A power supply runs most efficiently and quietly at around 40–60% of its capacity. A unit constantly running at its limit heats up more, gets louder and wears out faster. Headroom also lets you fit a more powerful graphics card later without replacing the power supply. But endless headroom isn't needed: a 1200 W unit for an office computer is money wasted.

Quality matters more than the number

A cheap no-name unit labelled "700 W" may in reality deliver far less reliably, with poor voltage regulation and no protections. A quality 550 W unit from a reputable maker is often better and safer. What to look for:

• A well-known maker and a model with independent reviews.
• Protections: against overload, overvoltage, short circuits and overheating.
• Capacity on the 12 V rail — that's what powers the processor and graphics card.
• An 80 Plus efficiency certificate — a measure of efficiency and, indirectly, of quality.
• The warranty — quality units often come with 7–10 years.

Connectors

Make sure the unit has the connectors you need: processor power (sometimes two), graphics card connectors including the new 16-pin ones for modern models, and enough drive connectors. Using adapters "from two drive connectors to the graphics card" is dangerous — the wires can overheat and melt.

What a weak or poor power supply can cause

• Sudden shutdowns and restarts under load, especially in games.
• Blue screens and instability.
• Shorter component life because of unstable voltage.
• Whining, humming or the unit itself overheating.
• At worst, the unit failing and damaging the board, graphics card or drives.

Tbilisi: power surges

Power surges and brief outages aren't unusual in Tbilisi, especially in older buildings and in bad weather. A quality power supply with protections copes better with these situations, but for expensive computers it's worth adding a voltage stabiliser or uninterruptible power supply as well. That protects both the power supply and your data.

Power supply lifespan

Even a good power supply ages: its capacitors lose capacity and its fan wears out. If the unit is more than 7–8 years old and you're fitting a powerful new graphics card, it makes sense to replace the power supply too.

A quality power supply is also one of the few components that can move from one build to the next. Spending a little more on a good unit today often means it serves two computers over its lifetime, which makes it better value than it first appears.

What our technician does

1. Calculates your configuration's real power draw, including peak loads.
2. Checks the condition of your existing power supply, its voltages and connectors.
3. Selects a quality power supply with the right capacity and protections.
4. Fits the unit with tidy cable routing and checks stability under load.
5. Recommends a stabiliser or UPS if electricity problems are frequent.

A real example

A gamer in Gldani fitted a new graphics card to an old "650 W" power supply from an unknown maker. The computer started shutting down in fast-moving game scenes, and one day, after a click, it wouldn't switch on at all. Our technician checked: the unit had failed, fortunately without damaging anything else. Its real capacity turned out to be far below what was claimed. We fitted a quality 750 W unit with 80 Plus Gold certification and a full set of protections, and recommended a UPS to guard against power surges. The shutdowns stopped.

Call a technician

If your computer shuts down under load or you're planning an upgrade, we'll come to any district of Tbilisi around the clock. Learn more on our component upgrades, computer won't turn on and computer keeps restarting pages.