Inverter Size Calculator

Inverter Size Calculator

Find the right inverter capacity for your load requirements.

Enter Your Values

Need to pick the right inverter? The Inverter Size Calculator helps you choose inverter power (VA/W) based on total appliance load, start-up (surge) currents for motors, and desired continuous runtime. Enter each appliance wattage or total load, add motor starting multipliers where needed, choose battery bank voltage, and the tool suggests minimum inverter continuous and peak (surge) ratings, and recommended battery/inverter pairings. This prevents overloads, ensures efficient inverter selection, and saves money by avoiding oversized or undersized choices.

Definition / Why it matters

Correct inverter sizing ensures continuous operation under load and handles surge currents of motors and compressors. Undersized inverters trip/fail; oversized inverters cost more and can be less efficient at low loads.

Formula(s)

  • Total continuous power (W) = Σ appliance wattages

  • Required inverter continuous rating (W) = Total continuous power × safety margin (1.2)

  • Surge rating = Highest motor start W × surge multiplier (2–6× depending on motor type)

  • Inverter VA rating = W ÷ Power Factor (PF, often 0.8–1.0)

Inputs (UI)

  • List of appliances (W) with quantity and whether inductive (motor)

  • System voltage (12/24/48 V)

  • Safety margin (%) (default 20%)

  • Power factor (default 0.8–1)

  • Desired backup hours (optional)

How to use

  1. Add appliances & wattages. 2. Mark motors/compressors. 3. Choose system voltage and safety margin. 4. Click Calculate → get suggested continuous W and surge VA, and recommended inverter model sizes.

Examples (5)

  • Lights + TV + Router = 300 W → suggested inverter 360–450 W

  • Refrigerator start 1200 W (run 200 W) → surge 2400–7200 W suggested inverter with matching surge capacity

  • AC (1500 W + compressor surge 4500 W) → pick inverter with 5 kW surge

Quick table

Load (W) Suggested Continuous Inverter (W) Suggested Surge (W)
500 600 1500
1500 1800 4500
3000 3600 9000

FAQs (6)

  • How much inverter for my house? → Sum loads + margin; consider fridge/AC surge.

  • Do inverters show both W and VA? → Yes, VA accounts for PF.

  • Can inverter run motor loads? → Only if rated for surge and continuous motor loads.

  • Should I oversize inverter? → Slightly oversize (10–25%)—not huge.

  • How does battery size affect inverter choice? → Voltage match & Ah capacity determine runtime.

  • Is pure sine wave required? → Motors and sensitive electronics prefer pure sine.

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