Choose a power supply by starting from your graphics card maker's recommended PSU rating, then pick a quality unit at or modestly above it with the connectors your parts need. Replace the PSU when it fails, becomes unstable under load, or is too small for new components. Wattage alone does not make a good unit: efficiency, protections and build quality matter as much.
How many watts does your PC actually need?
Add up what the heavy parts can draw at full load: the CPU's maximum power, the graphics card's board power, and a modest allowance for the motherboard, RAM, drives and fans. Then choose a supply with some headroom, so that typical gaming load sits around half to two-thirds of its rating. That is where most units run coolest and most efficiently.
The table gives realistic starting classes. They are guides, not rules, and the specific graphics card's recommendation always takes priority over them.
| PC type | Typical PSU class | Notes |
|---|---|---|
| Office or home PC, integrated graphics | Roughly 350 W to 450 W | Quality matters more than size here |
| Entry gaming, small graphics card | Roughly 450 W to 550 W | Check whether the card needs a PCIe power lead |
| Mid-range gaming | Roughly 550 W to 650 W | Common sweet spot for one 8-pin card |
| Strong graphics card plus a powerful CPU | Roughly 750 W to 850 W | Leaves room for upgrades |
| Top-end card or multi-drive workstation | 850 W and above, as the card maker advises | Choose carefully, as quality varies most here |
Newer high-end graphics cards can briefly draw well above their rated power in short spikes. Power supplies built to the newer ATX 3.x standard are designed to tolerate these. If you are buying for a card of that class, look for the standard on the box rather than relying on watts alone.
What separates a good PSU from a poor one at the same wattage?
Two supplies marked 650 W can behave very differently. The cheaper one may deliver that figure only on paper, run hot, and lack the protections that stop a fault from reaching your other parts. The power supply sits between the wall socket and every component in your PC, so it deserves a larger share of the budget than it usually gets.
- Efficiency rating. The 80 PLUS grades run from Bronze up through Titanium. A higher grade wastes less energy as heat. It says nothing on its own about build quality, so treat it as one factor.
- Protections. Look for over-voltage, under-voltage, over-current, over-power, short-circuit and over-temperature protection on the specification sheet. They are the safety net when something fails.
- A strong 12 V output. Modern PCs draw almost all their heavy load from the 12 V rail, so check the combined 12 V capability, not just the headline wattage.
- Warranty length. A long manufacturer warranty usually reflects confidence in the design.
- Independent reviews. Voltage stability and ripple can only be judged by measurement, so look for reviews from sites that use test equipment.
- Cable style. Fully modular units let you connect only the cables you need, which helps airflow and tidy building. Semi-modular and fixed-cable units cost less and work perfectly well if you route cables carefully.
Avoid unbranded units advertising very large wattages at very low prices. Their label figures are often peak or combined numbers, and they are a leading cause of failed power supplies and damaged components.
Which connectors should the new supply have?
Connector count is a quiet source of failed upgrades. A supply with enough watts but too few PCIe leads cannot run your graphics card. Check this list against both your motherboard and your graphics card before you buy.
- Motherboard power: a 24-pin ATX connector, which on most supplies splits into a 20-pin and a 4-pin section.
- CPU power: one 4+4-pin EPS lead, or two on boards with a high-end CPU.
- Graphics card power: the right number of 6+2-pin PCIe leads. Some newer cards instead use a single 16-pin high-power connector, and a cable made for that connector is better than a chain of adapters.
- Storage: enough SATA power leads for every drive you plan to fit.
- Form factor: standard ATX fits most towers, while small cases use the smaller SFX size.
Branded pre-built desktops sometimes use compact or non-standard power supplies and custom connectors. In those machines, an off-the-shelf ATX unit may not fit or plug in correctly, and the right replacement is the matching part.
When should you replace a power supply?
Replace it when it has failed, when it shows clear signs of failing, or when your PC has outgrown it. A supply cannot be safely repaired, because the capacitors inside can hold a dangerous charge long after it is unplugged. Never open the casing yourself, and do not accept advice to do so.
- The PC will not start, or restarts under load.
- You smell burning or notice a fan that is stalled, grinding or very loud.
- Cables are melted, discoloured or the connectors are damaged.
- A new graphics card or CPU takes you past what the supply can provide.
- A heavy power surge or lightning event has hit the PC.
Our guide to power supply warning signs describes what a failing unit tends to do before it dies. If the symptom is crashes in games, graphics card problems and crashes explains how to separate a power fault from a card fault.
One safety rule is easily missed. Never reuse the detachable cables from an old modular power supply in a new one. The pin layout on the supply end differs between makers and sometimes between models, and a mismatch can destroy components. Always use the cables that came with the new unit.
What does replacing a PSU cost?
Xigox's indicative price list shows 450W PSU replacement from ₹1,500 to ₹2,500, 650W gaming or workstation units from ₹3,000 to ₹5,000, and 850W and above for high-end gaming from ₹5,000 to ₹8,000. The final quote depends on brand, efficiency grade, modular design and your PC. The ₹350 inspection fee is refunded if you go ahead.
A replacement itself is straightforward: unplug and photograph the cabling, remove the old unit, fit the new one, route cables clear of fans, and test under load. In India it is worth pairing the new supply with a decent UPS or surge protector. Mains dips, spikes and cuts are the commonest reason supplies fail early, and our surge protection and UPS guide covers the options.
Frequently asked questions
Is a bigger power supply always better?
Not automatically. Extra capacity does no harm and gives upgrade room, but you pay more, and very large units can run slightly less efficiently at light loads. Buy the right size from a quality range.
Does a 750 W supply draw 750 W all the time?
No. A PC draws only what its parts need at that moment. The rating is the maximum the unit can deliver safely.
Can a bad power supply damage other parts?
Yes. Cheap or failing units with weak protection can pass dangerous voltages to the motherboard, drives or graphics card. That is a strong argument for not saving money on this part.
Is the 80 PLUS badge a guarantee of quality?
No. It certifies efficiency at set loads, not voltage stability, protections or longevity. Combine it with warranty length and independent reviews.
Can I fit a bigger PSU in a branded pre-built PC?
Sometimes, but the case, connectors and size can limit you. Check before buying, or have a technician confirm the fit.
If you are unsure which supply suits your parts, Xigox can inspect the PC, tell you what it needs and quote in writing before fitting anything. See the power supply replacement service, plan a new PC with the gaming PC build guide, check the price list, or book a free pickup.
