Induction Heating Power, Time and Energy Cost Calculator

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Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

Induction heating: Heating conductive metal with an alternating electromagnetic field, usually from a coil near the workpiece. [2]

Specific heat: The heat needed to raise one pound of a material by 1 F. This calculator uses Btu per lb-F.

Calculated temperature rise: Target temperature minus start temperature, expressed as Fahrenheit degrees for the thermal equation.

Overall electrical-to-part efficiency: The percent of generator input energy estimated to become heat in the part.

Additional heat-loss allowance: An extra percent added to ideal part heat for losses not already included in efficiency.

Electrical energy per part: Estimated generator input energy for one cycle, in kWh.

Variable electricity rate: The kWh-based charge from an electricity bill. It does not include fixed monthly or demand charges.

Mistake: Entering the full casting or assembly weight in Heated part weight when only a small zone is heated.
Fix: Enter only the metal mass that reaches the target temperature in this cycle.

Mistake: Entering a temperature rise in Start temperature or Target temperature.
Fix: Enter two actual temperatures. Target temperature must be higher than Start temperature.

Mistake: Treating Available generator power as power absorbed by the metal.
Fix: Enter the generator rating and adjust Overall electrical-to-part efficiency when measured or supplier process data is available.

Mistake: Using 8.71 as dollars in Variable electricity rate when Electricity-rate unit is $ per kWh.
Fix: Choose Cents per kWh for 8.71, or enter 0.0871 after choosing $ per kWh.

Mistake: Reducing Overall electrical-to-part efficiency and also adding the same losses in Additional heat-loss allowance.
Fix: Check Calculate and then recalculate. Leave Additional heat-loss allowance at 0 when the efficiency already includes coil, radiation, conduction, and setup losses.

Mistake: Reading Estimated variable electricity cost per part as the complete utility cost.
Fix: This output uses kWh-based energy charges only; fixed customer charges and peak-demand charges are excluded.

• This is a sensible-heat planning estimate based on heated weight, one average specific-heat value, and the entered temperature rise.
• It does not model coil geometry, coupling, frequency, magnetic changes, skin depth, part movement, or power control during the cycle.
• It excludes latent heat and phase changes. Do not use it alone where melting, major phase changes, or temperature-dependent material behavior matter.
• Efficiency defaults to 100 percent and additional heat-loss allowance defaults to 0 percent. These are ideal assumptions, not typical induction-system performance claims.
• Do not add a heat-loss allowance if the entered overall efficiency already includes those same losses.
• Estimated variable electricity cost per part includes only kWh-based cost. Fixed customer charges and peak-demand charges can change total plant cost but are not proportional to one cycle.
• Use measured kWh per part and actual heating trials to size equipment or approve a production process.

Thermal energy calculation

The calculator first finds the part temperature rise. A Celsius temperature difference is converted to Fahrenheit degrees by multiplying by 1.8.

ΔT (temperature rise in F) = target temperature - start temperature

Q (ideal heat in Btu) = heated part weight (lb) x specific heat (Btu per lb-F) x ΔT (F)

It converts Btu to kWh thermal using 0.00029307107 kWh per Btu.

Ideal part heat (kWh thermal) = Q (Btu) x 0.00029307107

Losses, energy, and the selected answer

Additional heat-loss allowance increases ideal part heat. Overall electrical-to-part efficiency then converts that adjusted part heat into estimated generator input energy.

Electrical energy per part (kWh) = ideal part heat x (1 + heat-loss allowance / 100) / (efficiency / 100)

In Required generator power mode, the calculator divides input energy by the target heat time. In Heating time mode, it divides input energy by available generator power.

Generator power needed (kW) = electrical energy per part x 3600 / target heat time (seconds)

Heating time (seconds) = electrical energy per part x 3600 / available generator power (kW)

For cost, cents per kWh are divided by 100 before multiplication. The default 8.71 cents per kWh is a May 2026 United States industrial planning estimate; replace it with the applicable kWh-based bill charge. [1]

Variable electricity cost per part ($) = electrical energy per part (kWh) x electricity rate ($ per kWh)

Worked example

A 10 lb part with specific heat 0.10 Btu per lb-F heated from 70 F to 1,070 F has a 1,000 F rise. Its ideal part heat is 10 x 0.10 x 1,000 = 1,000 Btu, or 0.29307107 kWh thermal. With 80 percent efficiency and a 10 percent added heat-loss allowance, estimated input energy is about 0.4030 kWh. Over 60 seconds, the estimated generator power needed is about 24.18 kW.

Assumptions and limits

The calculation uses an average user-entered specific heat and does not model changing material properties, phase changes, coil coupling, frequency, or power changes during heat-up. Electricity cost is a variable kWh cost only; fixed and demand charges are excluded.