CPU Power Consumption Calculator
Estimate CPU power draw and energy cost based on TDP and utilization level.
About CPU Power Consumption Calculator
CPU power draw isn't linear with utilization — dynamic power scales roughly with the square (or higher power) of clock frequency and voltage (P ∝ f·V²), and modern CPUs raise both together under load, so a super-linear exponent (commonly modeled between 1.5 and 2.0) approximates real-world power curves better than a straight-line interpolation between idle and TDP. Layering an idle power floor (CPUs never draw zero watts even fully idle, due to leakage current and always-on circuitry) onto that curve, then extrapolating to annual kWh (watts × 8760 hours/year ÷ 1000) and multiplying by local electricity rate gives a rough but useful ongoing cost estimate — useful for justifying more efficient hardware or power-capping decisions at scale.
Formulas
Power draw model
watts = idle_floor + (TDP − idle_floor) × (utilization/100)^exponent
- P_{idle}
- idle power floor
- P_{TDP}
- TDP (max sustained power)
- u
- utilization %
- n
- power scaling exponent
Annual energy consumption
annual_kWh = watts × 8760 / 1000
- P
- average power draw in watts
Worked example
With the default values below, CPU Power Consumption Calculator returns Estimated Power Draw (W) of 58.39. Change any input above and every figure here is recalculated in your browser.
Inputs used
- CPU TDP (Watts)minimum 1
- 125
- Average Utilization (%)accepts 0–100
- 55
- Power Scaling Exponentaccepts 1–3
- 1.5
- Idle Power Floor (% of TDP)accepts 0–50
- 10
- Electricity Cost ($/kWh)minimum 0
- 0.15
Results
- Estimated Power Draw (W)
- 58.39
- Estimated Annual Electricity Cost
- $76.72
- Estimated Annual Consumption (kWh)
- 511.48
- Max Possible Annual Consumption at 100% TDP (kWh)
- 1,095.00
- % of TDP Currently Drawn
- 46.71%
Step by step
- 1Values used
- 2Power draw model
- 3Annual energy consumption
- 4Estimated Power Draw (W)= 58.39
- 5Estimated Annual Electricity Cost= 76.72
- 6Estimated Annual Consumption (kWh)= 511.48
- 7Max Possible Annual Consumption at 100% TDP (kWh)= 1,095.00
- 8% of TDP Currently Drawn= 46.71
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why isn't TDP the same as actual power consumption?
TDP (Thermal Design Power) represents the sustained power draw the cooling system is designed to dissipate under heavy, sustained load — not a hard power cap and not the typical draw under normal, variable utilization. Real average power consumption is usually well below TDP unless the CPU is pegged at high utilization continuously.
Why does the power model use an exponent greater than 1 instead of linear scaling?
Dynamic power in CMOS circuits scales roughly with frequency times voltage squared (P ∝ f·V²), and modern CPUs raise both frequency and voltage together as load increases (DVFS), producing a super-linear relationship between utilization and power draw rather than a straight line from idle to TDP.
How can I measure actual CPU power draw on Linux?
Intel systems often expose RAPL (Running Average Power Limit) counters readable via `powertop` or directly from /sys/class/powercap/intel-rapl, giving real measured package power rather than an estimate. For a whole-system view including non-CPU components, a physical power meter at the wall remains the most accurate approach.