Generator Calculators & Converters

Generator Wattage Calculator

Add loads, include surge, get a recommended kW with headroom.

 Generator Fuel Consumption

Estimate L/gal per hour and daily/weekly/monthly cost at your load.

 Energy Consumption

Convert device power and hours into kWh and estimated costs.

 Generator Units Converter

kW, kVA, Amps & HP with PF, efficiency, and 1Ø/3Ø options.

 Power Units Converter

W, kW, MW, HP, BTU/h, TR and more—precise power conversions.

 Energy Units Converter

J, kWh, BTU, kcal, therms, toe, boe—convert energy effortlessly.

Planning, sizing, or comparing generators? Use our free, no-signup tools to estimate wattage needs, fuel use, and energy costs—and convert between common power and energy units in seconds. This guide explains when to use each tool, what the inputs mean, and tips for getting accurate results.

Which tool should I use?

1) Generator Wattage Calculator

What it does: Adds up your appliances’ running watts and accounts for starting (surge) watts for motors and compressors. It can calculate separate totals for 120 V and 240 V loads and suggests headroom (e.g., +20%).

Open the Wattage Calculator

How to use

  1. Search or pick an appliance from the list, or enter custom wattage.
  2. Set Qty and Voltage (120 V or 240 V).
  3. For motor loads (AC, pumps), include starting watts.
  4. Toggle Surge method: Typical (largest surge) vs. Conservative (sum of surges).
  5. Choose Headroom (10–30%) and review the recommended generator size.

Tips for accuracy

  • Use the appliance nameplate or manual when possible.
  • Not all loads run at once; plan for realistic simultaneous use, but never undersize critical circuits.
  • Split-phase generators: keep 120 V legs reasonably balanced.

2) Generator Fuel Consumption Calculator

What it does: Estimates fuel use per hour/day/week/month and cost from generator size (kW or kVA), load %, and SFC presets (diesel/gasoline) or a custom SFC.

Open the Fuel Calculator

Inputs explained

  • Rated Power: nameplate kW (or kVA with power factor).
  • Load (%): average percent of rated output you expect to use.
  • SFC: fuel per kWh (e.g., 0.24 L/kWh for diesel); choose a preset or enter your own.
  • Hours/day and Fuel price for daily/weekly/monthly cost projections.

Example

50 kW diesel generator at 60% load, SFC 0.24 L/kWh, 8 h/day, diesel at $1.60/L:

  • Per hour: ~7.2 L
  • Per day (8 h): ~57.6 L
  • Cost/day: ~$92.16

Note: SFC varies by engine size, age, altitude, temperature, and the manufacturer’s load curve. Use manufacturer data when available.

3) Energy Consumption Calculator

What it does: Converts an appliance’s power (W or kW), quantity, and hours/day into kWh per day/month/year and estimates electricity cost at your local price per kWh.

Open the Energy Consumption Calculator

Quick start

  1. Select a typical appliance or type watts manually.
  2. Set quantity and daily hours of use.
  3. Optionally enter a price per kWh to see costs.

Example: A 1,500 W space heater used 4 h/day costs about 6 kWh/day. At $0.20/kWh, that’s ~$1.20/day (≈$36/month if used daily).

4) Converters

Generator Units Converter

What it does: One-stop motor/generator math: convert between kW, kVA, amps (single- or three-phase), horsepower, and include power factor (PF) and efficiency.

Open Generator Units Converter

  • KW ↔ Amps with PF and phase (√3 factor for 3-phase).
  • KW ↔ KVA with PF.
  • HP ↔ kW/kVA with efficiency (mechanical ↔ electrical).

Power Units Converter

What it does: Converts between W, kW, MW, HP (mechanical), PS (metric hp), BTU/h, TR, and more.

Open Power Units Converter

Energy Units Converter

What it does: Converts between J, kJ, MJ, kWh, MWh, BTU, kcal, therms, toe, boe, ton TNT, etc.

Open Energy Units Converter

Best practices for sizing and budgeting

  • Collect nameplate data for key loads (A/W, voltage, phase, PF if shown).
  • Account for starting watts (compressors, pumps, AC units). If unsure, use conservative surge settings.
  • Add headroom (typically 15–30%) for voltage dips, altitude/temperature derating, and future loads.
  • Balance split-phase loads across 120 V legs when using 240 V generators.
  • Fuel is tied to load, not just generator size. Lower average load = less fuel per hour.
  • Validate with real measurements (clamp meter, energy monitor) when possible—especially for mission-critical systems.

Frequently Asked Questions

How accurate are these tools?

They’re designed for planning and quick estimates. Results depend on the quality of your inputs (nameplate values, actual load %, SFC). For final system design, consult the manufacturer’s specs or a qualified electrician.

What headroom should I choose for generator sizing?

Many users select +20% to cover surge, environmental derating, and short-term peaks. Critical applications may use 25–30% or more.

Does the Fuel Calculator support diesel and gasoline?

Yes. Choose a preset SFC for diesel or gasoline, or enter your own SFC from manufacturer data. Costs can be shown per hour/day/week/month using your local fuel price.

Can I use these tools on mobile?

Yes. All calculators and converters are mobile-friendly and work in the browser—no login or install required.

What’s the difference between power (kW) and energy (kWh)?

kW measures rate (instantaneous power). kWh measures total energy over time (power × time). A 1 kW device running for 2 hours uses 2 kWh.

Disclaimer: The tools provide estimates only and are not a substitute for professional design or safety guidance.

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