CMOS power consumption (αCV²f) calculator
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KEY POINTS
CMOS dynamic power is P = α·C·V²·f; because it scales with the square of voltage, lowering voltage by 20% cuts dynamic power by 36%. As voltage approaches the threshold, however, maximum frequency drops sharply and tasks take longer, so leakage is paid for longer. Rising leakage with scaling is also why frequency gains stalled and processors turned to multiple cores.
Inputs
Switched capacitance is the sum of gate and wire capacitance. To estimate it from gate count, use gate count × capacitance per gate (about 0.5 to 1 fF at leading-edge nodes) as a guide. The DVFS calculation simplifies leakage current as proportional to voltage.
Supply voltage and power (DVFS, frequency at its maximum for each voltage)
Frequency and power at different voltages
| VDD | Maximum frequency | Power | Power per frequency |
|---|---|---|---|
| 0.450 V | 1.20 GHz | 1.30 W | 1088 mW/GHz |
| 0.525 V | 1.74 GHz | 2.25 W | 1291 mW/GHz |
| 0.600 V | 2.21 GHz | 3.47 W | 1568 mW/GHz |
| 0.675 V | 2.63 GHz | 4.99 W | 1897 mW/GHz |
| 0.750 V | 3.00 GHz | 6.82 W | 2272 mW/GHz |
| 0.825 V | 3.33 GHz | 8.96 W | 2689 mW/GHz |
| 0.900 V | 3.63 GHz | 11.43 W | 3146 mW/GHz |
Why lowering voltage works best
Each time a CMOS transistor switches, it charges or discharges its load capacitance and spends CV² of energy. Dynamic power scales with the square of voltage, so lowering voltage by just 20% cuts dynamic power by 36%. Smartphone and server processors manage power with DVFS, lowering voltage and frequency together as load drops.
As voltage approaches the threshold, however, drive current falls and maximum frequency drops sharply, so tasks take longer and leakage is paid for longer. The difficulty of lowering threshold voltage with scaling (rising leakage) is a major reason clock frequencies stopped climbing in the mid-2000s and processors turned to multiple cores.
FAQ
Why does lowering voltage save so much power?
Dynamic power scales with V², so a 20% voltage reduction alone cuts it to 64%, before any frequency reduction.
What is DVFS?
Dynamic voltage and frequency scaling lowers voltage and frequency together when the load is light, and raises them when performance is needed.
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Last updated: October 23, 2026