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Home Load Calculator: Size Your Inverter, Battery and Solar System Correctly

Choosing the wrong inverter or battery size is one of the most common (and expensive) mistakes people make when setting up home power backup. The Home Load Calculator solves this by letting you select your home appliances from a built-in list of 150+ items (or add a custom device) and it instantly calculates your connected load, running load and daily energy use. Based on this, it recommends the correct inverter capacity, battery size and solar panel setup – all in one place. This tool is useful for diploma and B.Tech electrical students learning load calculation basics, as well as working professionals and homeowners who want an accurate, no-guesswork backup system for their house.

How to Use

1. Click Add Appliance and select an item from the dropdown list (fan, fridge, TV, etc.) or click Add Custom Device to enter your own appliance name.
2. Enter the Quantity (how many of that appliance you have) and its Power in Watts (found on the appliance label or box).
3. Enter the Hours/Day you use it and select the Usage Type – “Continuous” if it runs 3+ hours at a stretch (like a fridge) or “Non-Continuous” for on-off use (like lights).
4. Repeat for all your appliances, then click Calculate Load.
5. Review your results: Load Summary, Bill Estimate, Inverter size, Battery size and Solar panel size.
6. Use Save as PDF or Copy Result to keep a record or Reset All to start over.

Key Features

• Built-in database of 150+ common home appliances across 17 categories
• Automatic detection of motor-type appliances (fridge, pump, AC) with surge/starting current handling
• Instant electricity bill estimate with an adjustable rate per unit (₹/kWh)
• Inverter sizing in Watts, VA and kVA with Pure Sine Wave recommendation when needed
• Battery sizing calculator with adjustable system voltage (12V/24V/48V) and backup time (1–8 hours)
• Solar panel sizing with selectable panel wattage (335W to 600W)
• Add unlimited custom devices not in the default list

Formula / Logic Used

Connected Load and Running Load

The tool first adds up the total power of all selected appliances, then applies a higher factor for continuous-use devices because they draw steady load for longer periods.$$Running\ Load = \sum (Watts \times Quantity \times Factor)$$Where:

• Watts = power rating of the appliance
• Quantity = number of units
• Factor = 1.25 for continuous use (3+ hours non-stop), or 1 for non-continuous use

Inverter Sizing$$Inverter\ Watts = Running\ Load \times 1.2$$$$Inverter\ VA = \frac{Inverter\ Watts}{0.8}$$

Where:

• 1.2 = 20% safety margin added above your running load
• 0.8 = standard power factor used to convert Watts into VA (Volt-Amps), the unit inverters are usually rated in

Battery Sizing (at 12V, default 4-hour backup)$$Battery\ Ah = \frac{Running\ Load \times Backup\ Hours}{System\ Voltage} \times 1.2$$

Where:

• Backup Hours = how long you want power during a cut (default 4 hours, adjustable)
• System Voltage = 12V, 24V or 48V battery bank
• 1.2 = 20% extra capacity margin

Solar Panel Sizing$$Solar\ Required\ Watts = \frac{Daily\ Energy\ (Wh) \times 1.3}{5}$$

Where:

• Daily Energy = total Wh your appliances consume per day
• 5 = average peak sunlight hours per day (standard assumption for India)
• 1.3 = 30% margin for system losses and cloudy days

Who Should Use This Tool

• Homeowners planning to buy an inverter, UPS or solar system and want the correct size, not a guess
• Diploma and B.Tech Electrical Engineering students learning practical load calculation and inverter/battery sizing basics
• Electricians and site engineers who need a quick, reliable sizing reference for client homes

Frequently Asked Questions (FAQs)

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Related Tools

• Cable Size Calculator – once you know your load, size the correct wiring for it
• Voltage Drop Calculator – check if your wiring run causes excessive voltage drop under this load
• Transformer Calculator – useful if you’re sizing power equipment beyond just home backup

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