Beyond picking the right PSU, it’s often useful to know roughly what your PC actually costs to run — whether you’re budgeting monthly electricity costs, comparing two possible builds, or just curious how much that GPU upgrade adds to your bill. This calculator estimates your system’s power draw at idle and under gaming load, and converts that into an approximate running cost using your local electricity rate. It’s aimed at anyone planning a build, comparing components, or trying to understand where their PC’s power actually goes.
What the Result Means
You’ll typically see two power figures — an idle draw (what your system uses sitting at the desktop or doing light tasks) and a load draw (what it uses under sustained gaming or heavy workloads) — plus a cost estimate based on hours of use per day or week and your electricity price per kWh. Idle draw is dominated by the baseline power the motherboard, RAM, storage, and fans need just to stay on, plus a much lower CPU and GPU draw since neither is being pushed. Load draw scales up mainly because of the CPU and especially the GPU, which is usually the single biggest power consumer in a gaming PC once it’s under load.
The cost figure is a straightforward multiplication of estimated wattage, hours of use, and your electricity rate — it’s only as accurate as those inputs, so getting your real electricity rate and a realistic estimate of your daily usage hours matters more than anything else for that number.
How This Calculator Works
The calculator estimates idle power as a smaller baseline figure built from typical low-load consumption for the motherboard, RAM, storage, and fans, plus the CPU and GPU each running near their minimum power states. Load power is estimated by taking the CPU and GPU close to their rated TDP figures (since that’s a reasonable proxy for sustained gaming load on those two parts) and adding the same baseline system draw on top. The wattage figures are then converted to kilowatt-hours over your specified usage time and multiplied by your entered electricity price to produce a cost estimate, usually shown per day, month, and year.
Worked example: Consider a system idling around 60-70W and reaching roughly 350W under load with a Ryzen 5 7600 (65W TDP) and an RTX 4070 (200W TDP) plus baseline system draw. If you game for 3 hours a day at that load figure and leave the PC idling for another 3 hours of light use, that’s roughly (350W × 3h) + (65W × 3h) = 1050Wh + 195Wh ≈ 1.25 kWh per day. At an electricity price of $0.15 per kWh, that’s about $0.19 per day, or roughly $5.60 a month — small on its own, but a useful number when comparing it against a higher-power build.
Important Limitations
This is an estimate built from typical TDP figures and baseline draw assumptions, not a measurement taken from your specific PC with a wattmeter. Actual draw depends on the specific game or workload (some games barely tax a GPU while others push it to its power limit constantly), monitor refresh rate and resolution, background applications, power-saving settings in your OS and BIOS, ambient temperature, and the specific silicon in your CPU and GPU, which can vary unit to unit. PSU efficiency also means the wattage pulled from the wall is somewhat higher than the wattage your components actually receive.
Electricity rates vary significantly by region, time of day (if you’re on a variable-rate plan), and season, and this calculator uses whatever flat rate you enter rather than pulling a live utility rate. Treat the cost output as a reasonable planning figure for comparing builds or estimating a monthly budget, not as a guaranteed bill amount — if you want a precise number, a plug-in power meter on your actual PC is the only way to measure real draw directly.
Frequently Asked Questions
Why does my PC use so much more power under load than at idle?
Because the CPU and especially the GPU scale their power draw enormously based on how hard they’re working. At idle, both parts sit at a low-power state; under a demanding game, the GPU in particular can draw several times its idle power, which is why load figures are so much higher than idle figures.
Does resolution affect power consumption?
Yes, indirectly. Higher resolutions typically push the GPU harder, which increases its power draw toward its rated limit, while lower resolutions on a powerful GPU may let it idle at a lower power state more often, especially if a frame rate cap is in place.
How can I actually lower my PC's power draw?
Undervolting the CPU or GPU, capping your frame rate to what your monitor needs, enabling power-saving BIOS settings, and choosing more power-efficient components at your next upgrade are the most effective levers, roughly in that order of effort versus payoff.
Is this the same as my PSU wattage?
No. Your PSU’s wattage rating is its maximum safe capacity, sized with headroom above your typical draw. This calculator estimates what your components actually consume, which should be comfortably below your PSU’s rated wattage during normal use.
Why is my estimated cost different from my actual electricity bill?
Your bill includes other devices, your utility’s exact rate structure (tiered rates, time-of-use pricing, fixed fees), and your PC’s real usage pattern, none of which this calculator can see — it only estimates the PC’s own draw at the rate and hours you enter.