Choosing the right inverter size is the most important decision when building a solar or backup power system. Get it wrong and you either have a system that trips under load, or you overspend on capacity you will never use.
Step 1: List Your Appliances
- Write down every appliance you want to power and its wattage:
- LED bulbs: 5–15W each
- Ceiling fans: 60–80W
- 32" TV: 60–100W
- Laptop: 45–65W
- Refrigerator: 150–200W (starting surge can be 3x this)
- 1HP air conditioner: ~750W running, ~2,000W starting surge
Step 2: Add Up Running Watts
Add the running watts of all appliances you will use simultaneously. This is your minimum inverter capacity.
Step 3: Account for Surge Power
Motors (fans, fridges, ACs) draw 2–3x their running wattage when starting. Your inverter must handle this surge. A 1kVA inverter can typically handle a brief 2kVA surge.
Step 4: Add a Safety Margin
Never run an inverter at more than 80% of its rated capacity continuously. Multiply your total running load by 1.25 to get the minimum inverter size.
Example Calculation
- 5 LED bulbs (50W) + 2 fans (160W) + TV (80W) + Fridge (200W) = 490W running
- With surge allowance for fridge: 490 + 400 = 890W
- With 25% safety margin: 890 × 1.25 = 1,112W
- Recommended inverter: 1.5kVA minimum
Use our Load Calculator on the website for an automatic calculation. Or WhatsApp us and we will calculate it for free.