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Voltage Regulator Power Loss Calculator

Work out voltage regulator power loss instantly with clear inputs, formula shown and shareable results.

About Voltage Regulator Power Loss Calculator

A linear regulator drops the excess voltage as heat: loss is (Vin - Vout) times load current, plus the quiescent current times input voltage. Efficiency is therefore roughly Vout/Vin, so dropping 12 V to 5 V wastes more than 40% of the input power whatever the load.

Formula

Linear regulator loss

P = (Vin - Vout) x Iload + Vin x Iq; efficiency approx Vout / Vin

Worked example

With the default values below, Voltage Regulator Power Loss Calculator returns Power dissipated in the regulator of 5.66. Change any input above and every figure here is recalculated in your browser.

Inputs used

Input voltage
12 V
Output voltage
5 V
Load current
800 mA
Quiescent current
5 mA

Results

Power dissipated in the regulator
5.66 W
Efficiency
41.41% %
Useful output power
4.00 W
Input power
9.66 W

Step by step

  1. 1Values used
  2. 2Linear regulator loss
  3. 3Power dissipated in the regulator= 5.66 W
  4. 4Efficiency= 41.41 %
  5. 5Useful output power= 4.00 W
  6. 6Input power= 9.66 W

Assumptions and limits

  • The result is derived only from the 4 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.
  • Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

Frequently Asked Questions

When is a linear regulator still the right choice?

When the drop is small, the current is low, or output noise must be very low — an LDO after a switcher is a common combination.

Why does efficiency not depend on load?

Because both output power and dissipation scale with current, so the ratio stays near Vout/Vin until quiescent current dominates at very light load.

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