PC Power Supply Calculator

About This PC Power Supply Calculator

Choosing the wrong PSU is one of the most common PC building mistakes. An undersized PSU can cause system instability, sudden shutdowns, and hardware damage during GPU power spikes. An oversized PSU wastes money and runs at reduced efficiency. This calculator helps you find the sweet spot: enough headroom for transient power spikes without paying for capacity you will never use.

The calculator also includes a unique Solar Bridge feature for solar professionals and eco-conscious builders. After calculating your PC's power draw, it tells you exactly how many solar panels and battery storage capacity you need to run the system off-grid or to fully offset its annual grid consumption. This is useful for solar workstation builds, off-grid content creation setups, and clients who want to power their home office with solar.

All efficiency calculations reference the 80 Plus certification tiers (Bronze, Silver, Gold, Platinum, Titanium) so you can choose a PSU that minimizes electricity waste and reduces the wall draw below the nameplate system wattage.

Component-by-Component Analysis

Enter CPU TDP, GPU TDP, RAM count, SSD and HDD count, and fan count for a precise wattage breakdown showing the contribution of each component to total system draw.

ATX 3.0 Ready

Flags when system wattage exceeds ATX 2.0 PSU limits and recommends ATX 3.0 compliance for GPUs with 12VHPWR connectors like the RTX 4080/4090 that can draw 600W+ in transient spikes.

Solar Bridge Calculator

Calculates how many solar panels and kWh of battery storage are needed to fully power the PC off solar, bridging PC building and solar energy planning in one tool.

How to Use This Calculator

Enter CPU Wattage

Find your CPU's TDP (Thermal Design Power) on the manufacturer spec sheet or on sites like CPUBenchmark.net. Intel Core i9 chips are typically 125-253W; AMD Ryzen 9 chips are typically 105-170W. Use the actual TDP, not the turbo boost figure, for accurate baseline calculations.

Enter GPU Wattage

Find your GPU's Total Board Power (TBP) on the manufacturer spec sheet. This is the most important input: RTX 4060 is 115W, RTX 4080 is 320W, RTX 4090 is 450W. The GPU is typically 50-70% of total system draw in gaming or rendering builds.

Enter RAM, Storage, and Cooling

Input the number of RAM sticks (each approximately 3W), SSDs (approximately 5W each), HDDs (approximately 8W each), and case fans (approximately 3W each). These components contribute 20-60W in a typical build, significant enough to affect PSU tier selection.

Select PSU Efficiency Tier

Choose your target 80 Plus certification level: Bronze (85% efficient), Silver (88%), Gold (90%), Platinum (92%), or Titanium (94%). Higher efficiency means less heat, lower electricity costs, and a longer PSU lifespan, though Platinum and Titanium carry a price premium.

Review Your PSU Recommendation

The calculator outputs the recommended PSU wattage with 30% headroom, actual wall draw from the outlet accounting for efficiency losses, annual electricity cost, and the number of solar panels needed to offset the PC's annual energy consumption.

Understanding Your Results

Total Component Draw

480 W

The sum of all component TDP values. This is the DC load your PSU must deliver. Note that components rarely run at 100% TDP simultaneously during normal use; this represents the worst-case sustained load.

Recommended PSU Wattage

750 W

The minimum PSU wattage recommended, which is total component draw multiplied by 1.30 (30% headroom). Always buy the next standard PSU tier above this number: 550W, 650W, 750W, 850W, 1000W, 1200W, or 1600W.

Wall Draw (from outlet)

530 W

The actual power drawn from your wall outlet, which is higher than component draw due to PSU conversion losses. A 90% efficient (80 Plus Gold) PSU delivering 480W DC draws approximately 533W AC from the wall.

Annual Energy Cost

$213/yr

Estimated annual electricity cost based on your wall draw, usage hours per day, and your local electricity rate. Assuming 8 hours per day at $0.14/kWh as the national average baseline.

Solar Panels to Power PC

2 panels

The number of 400W solar panels needed to fully offset the PC's annual energy consumption, based on location PSH, 80% system efficiency, and daily usage hours. A typical gaming PC requires 1-3 panels to offset annual consumption.

When to Use This Tool

New PC Build

Before purchasing a PSU for a new build, run every component configuration through this calculator to confirm PSU wattage. Avoid the common mistake of buying a 650W PSU for a build that needs 720W with headroom, requiring a costly return and exchange.

PSU Upgrade

When upgrading a GPU in an existing system, recalculate total system draw. An RTX 3070 at 220W replaced by an RTX 4080 at 320W adds 100W of load. A 650W PSU that was adequate before may be undersized after the upgrade.

Solar Powering a Workstation

Solar professionals designing off-grid workstations or solar-powered home offices use the Solar Bridge output to specify the correct array and battery size for reliably powering high-draw computing workloads without grid connection.

Pro Tips and Common Mistakes

GPU Is the Biggest Draw (Up to 450W for RTX 4090)

In gaming and rendering builds, the GPU accounts for 50-70% of total system power. An RTX 4090 has a 450W TBP but can spike to 600W+ transient in games with poor optimization. Never size a PSU based only on average GPU draw; always account for peak transient spikes.

80 Plus Gold or Platinum Efficiency Matters

Moving from Bronze (85% efficiency) to Gold (90% efficiency) on a 500W system saves approximately 29W of heat and waste. Over 8 hours per day at $0.15/kWh that is $12.70 per year in savings. Platinum or Titanium PSUs pay back the price premium within 2-4 years for high-usage systems.

ATX 3.0 for 12VHPWR Connectors

GPUs with 16-pin 12VHPWR connectors (RTX 40-series, RX 7000-series) can draw up to 600W in transient spikes under ATX 2.0. ATX 3.0 PSUs are designed to handle 200% transient overloads without shutting down. Any build with an RTX 4080 or higher should use an ATX 3.0 certified PSU.

Size for GPU Power Spikes Not Sustained Draw

PSU sizing should account for the worst-case transient load, not the average TDP. Add 20-30% to the GPU TBP figure to estimate peak spike draw when selecting PSU capacity. This is separate from the 30% system headroom this calculator applies; both are necessary for reliable operation.

PSU Wattage Tier Quick Reference

PSU Wattage	Typical Use Case	GPU Tier	ATX 3.0 Recommended
450W	Office / HTPC	Integrated graphics or GT 1030	No
550W	Basic Gaming	RTX 4060 (115W) / RX 7600	No
650W	Mid-Range Gaming	RTX 4060 Ti (160W) / RX 7700 XT	No
750W	High-Performance Gaming	RTX 4070 Ti (285W) / RX 7900 GRE	Recommended
850W	Enthusiast Gaming	RTX 4080 (320W) / RX 7900 XT	Required
1000W	High-End Gaming / Creator	RTX 4090 (450W) single GPU	Required
1200W	Extreme / Dual GPU	RTX 4090 + high CPU or SLI	Required
1600W+	Workstation / Mining	Multi-GPU or high-core server CPU	Required

Methodology: How We Calculate PSU Requirements

The PSU calculation follows a five-step process from component wattage through to solar offset sizing. All formulas are based on standard electrical engineering principles and 80 Plus efficiency certification data.

Step 1: Total Component Draw

DC Component Load

Total_DC = CPU_TDP + GPU_TBP + (RAM_sticks x 3W) + (SSD_count x 5W)
         + (HDD_count x 8W) + (Fan_count x 3W) + Misc_draw

Step 2: Recommended PSU Minimum

PSU Minimum with 30% Headroom

PSU_min_W = Total_DC x 1.30
Round up to next standard tier: 450/550/650/750/850/1000/1200/1600W

Step 3: Wall Draw (AC from outlet)

AC Wall Draw

Wall_Draw_W = PSU_min_W / PSU_efficiency
Where PSU_efficiency:
  Bronze  = 0.85
  Silver  = 0.88
  Gold    = 0.90
  Platinum= 0.92
  Titanium= 0.94

Step 4: Annual Electricity Cost

Annual Energy Cost

Daily_kWh   = Wall_Draw_W x hours_per_day / 1000
Annual_kWh  = Daily_kWh x 365
Annual_Cost = Annual_kWh x electricity_rate_per_kWh

Step 5: Solar Panels to Power PC

Solar Panel Count

Solar_kWh_needed = Annual_kWh
Panel_annual_gen  = Panel_W x PSH_per_day x 365 x 0.80 / 1000
Panel_count       = CEIL(Solar_kWh_needed / Panel_annual_gen)
Default: 400W panel, 4.5 PSH/day, 80% system efficiency

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Frequently Asked Questions

Why do I need 30% headroom in a PSU?

PSUs operate most efficiently and reliably at 50-80% of their rated capacity. Running a PSU above 90% rated wattage causes excessive heat, accelerated capacitor degradation, and risk of shutdown during transient power spikes. The 30% headroom keeps the PSU in its optimal efficiency range and provides buffer for GPU power spikes that can be 2-3x the rated TBP in millisecond bursts.

What is the 80 Plus efficiency rating?

The 80 Plus certification program tests PSUs under standardized loads and certifies that they operate at 80% efficiency or better across load conditions. Tiers are: Standard (80%), Bronze (85%), Silver (88%), Gold (90%), Platinum (92%), and Titanium (94%). A Gold PSU delivering 500W DC draws only 556W AC from the wall, versus 625W AC for an uncertified 80% efficient unit. The difference is 69W of heat and wasted electricity.

What PSU do I need for an RTX 4090?

NVIDIA recommends a minimum 850W PSU for the RTX 4090. In practice, with a high-TDP CPU (i9-13900K at 253W, for example), total system draw can reach 700-750W, making a 1000W ATX 3.0 PSU the correct choice with 30% headroom. The RTX 4090 uses a 16-pin 12VHPWR connector and can spike to 600W transient, requiring an ATX 3.0 compliant PSU to handle that transient without triggering overcurrent protection.

Modular vs non-modular PSU: which is better?

Fully modular PSUs allow you to connect only the cables you need, improving airflow and cable management. Semi-modular PSUs have fixed cables for the 24-pin ATX and CPU EPS connectors, with modular connectors for GPU and storage. Non-modular PSUs have all cables fixed, which can cause cable clutter. For most builds, semi-modular is the best value balance. Modular is ideal for small form factor cases where cable management is critical.

How long should a quality PSU last?

A quality PSU from a reputable brand (Seasonic, Corsair, EVGA, be quiet!) rated at Gold or higher typically lasts 7-12 years with normal use. Most quality PSUs carry 10-year warranties. The main failure points are capacitors and the fan. PSUs running at 50-80% capacity in a well-ventilated case last significantly longer than those constantly running at 90%+ capacity in hot environments.

What is ATX 3.0 vs ATX 2.0?

ATX 3.0 is the updated power supply standard released in 2022, designed to support modern high-power GPUs. Key differences from ATX 2.0: ATX 3.0 includes native 16-pin 12VHPWR connector support, requires handling transient spikes up to 200% of rated power for 100 microseconds without shutting down, improves transient response speed, and adds stricter efficiency requirements at low loads. For RTX 4080 and above, ATX 3.0 is strongly recommended.

Can solar power a PC?

Yes. A typical gaming PC drawing 300-400W from the wall needs approximately 1-2 panels worth of solar generation to offset annual energy consumption (about 1,000-1,500 kWh/year). For a fully off-grid solar workstation running during daylight hours, a 2-3kW solar array with 10-20 kWh of battery storage can reliably power most gaming or content creation setups. The Solar Bridge output in this calculator gives you the starting numbers for that sizing conversation.

How do I size a UPS for my PC?

Size a UPS (Uninterruptible Power Supply) based on your wall draw in VA (volt-amperes), not watts. Divide watts by 0.8 (power factor) to get VA: a system drawing 500W from the wall needs a 625VA UPS minimum. For 15 minutes of runtime during an outage, multiply VA by 15 minutes, then adjust for battery efficiency (typically 85%). Most manufacturers provide runtime charts for their specific units.

What PSU do I need for a crypto mining rig?

Mining rigs run GPUs at sustained 100% load 24/7, which is far more demanding than gaming. For a 6-GPU mining rig using RTX 3060 Ti cards at 200W each (after undervolting), total GPU draw is 1,200W. Add CPU, motherboard, and fans for approximately 1,400W total. You need a 1,600-2,000W PSU with 80 Plus Gold or Platinum efficiency. Some miners use dual PSUs linked with an add-on controller board to share the load across two units.

Does undervolting a GPU reduce PSU requirements?

Yes significantly. Undervolting reduces a GPU's core voltage below stock settings, reducing power draw by 10-25% while maintaining the same clock speed in most cases. An RTX 4090 undervolted from 450W TBP to 350W reduces system draw by 100W, potentially allowing a 1000W PSU instead of a 1200W unit. Undervolting also reduces heat, noise, and GPU degradation over time. Tools like MSI Afterburner make undervolting accessible for enthusiast users.

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