Inverter Load Calculator - VA & Battery AH from Appliance Load
Size inverter VA and battery AH from your total appliance load - add custom wattages, use 1BHK/2BHK/3BHK or bedroom presets, and set backup hours for instant VA and amp-hour recommendations. Supports India, US, and EU quick-start configurations.
Total Load
340W
Suggested
850VA
Backup
4.5 Hrs
Recommended Battery
150 AH (12V)
System Setup
Region, housing preset, and backup settings
Region
Quick Presets
Appliance Management
Configure your load requirements
LED Bulb
Standard energy-efficient lighting
Ceiling Fan
Standard 48-inch ceiling fan
LED TV
32-43 inch LED television
Wi-Fi Router
Home internet router
Laptop Charger
Laptop power adapter
Methodology and limitations
Last reviewed:
Methodology
Sums appliance wattage by quantity, applies power factor and safety margin for inverter VA, and divides energy demand by battery voltage and efficiency for AH. Results round up to standard market sizes.
Limitations
Motor startup surge, cable losses, battery aging, and temperature can affect real-world performance. Consult an installer for final sizing.
How Inverter VA and Battery AH Are Sized
Size inverter VA and battery AH from your total appliance load - add custom wattages, use 1BHK/2BHK/3BHK or bedroom presets, and set backup hours for instant VA and amp-hour recommendations. Supports India, US, and EU quick-start configurations.
Method used
The calculator sums running appliance wattage, converts to inverter VA using power factor and a safety margin, then divides energy demand by battery voltage and efficiency to recommend amp-hour capacity for the selected backup hours.
VA = (total watts ÷ power factor) × safety margin; AH = (watts × backup hours) ÷ (voltage × efficiency)
Practical example
A 1BHK load of 450 W with 0.8 power factor, 1.2 safety margin, 4 backup hours, 12 V battery, and 85% efficiency might suggest roughly 850 VA inverter and 180 AH battery (rounded to market sizes).
- Appliance list with wattage and quantity
- Backup hours, battery voltage, power factor
- Housing preset or custom load
The result shows total load watts, recommended inverter VA, battery AH, and rounded standard market sizes.
Assumptions
- All listed appliances may run simultaneously unless you adjust the load.
- Power factor defaults to 0.8 for mixed household loads.
- Results round up to common inverter and battery sizes.
What this includes
- Load wattage total, inverter VA sizing, battery AH sizing, housing presets, and advanced efficiency settings.
What this excludes
- Motor startup surge beyond steady-state VA, cable voltage drop, battery aging, solar charging integration, and installer-certified final design.
Related calculators
Frequently Asked Questions
How do I calculate inverter VA from appliance load?
Add the wattage of all appliances you expect to run at the same time, divide by the power factor (typically about 0.8 for mixed household loads), and apply a safety margin. The calculator rounds up to common inverter sizes such as 600, 850, or 1000 VA. Always recheck nameplate watts—especially for motors—before purchasing hardware.
How is battery AH calculated for backup power?
Multiply total load in watts by desired backup hours, then divide by battery voltage and inverter efficiency to estimate amp-hours. Enable depth-of-discharge limits in advanced settings for a more conservative bank size that avoids draining batteries too deeply. Real runtime also depends on temperature, battery age, and simultaneous surge loads.
What is the difference between VA and watts?
Watts measure real power consumed by appliances. VA (volt-amperes) is apparent power the inverter must be able to supply. Motors and other inductive loads often draw more VA than their running watts, which is why inverters are rated in VA. Undersizing VA causes overload trips even when average watts looked acceptable on paper.
Should I use 12V, 24V, or 48V batteries?
12V systems are common for small apartments and light loads. 24V and 48V banks suit larger continuous loads because higher voltage reduces current and cable losses for the same power. Match battery bank voltage to your inverter’s DC input rating, and follow manufacturer wiring guidance for series/parallel packs.
What are 1BHK, 2BHK, and 3BHK presets?
These India-style housing presets (1, 2, or 3 bedroom-hall-kitchen layouts) pre-fill typical appliance mixes so you can size VA and AH quickly. US and EU presets use bedroom-based labels with region-appropriate wattages. Treat presets as starting points—edit individual loads to match the devices you actually need during an outage.
Do motors need extra inverter capacity?
Yes. Refrigerators, air conditioners, and pumps can draw two to three times their running watts at startup. Choose an inverter with surge capacity above the steady-state VA shown here, or sequence motor starts so they do not spike together. Ignoring startup current is a frequent cause of nuisance shutdowns on otherwise “correct” VA math.