Buy an inverter that is too small and it trips every time the fridge compressor starts. Buy one that is too big and you pay for capacity you never use. The good news: sizing a hybrid solar inverter takes about ten minutes and a pen.
Step 1: List what must run during a power cut
Write down every appliance you want running at the same time when the grid is off, with its wattage. The rating plate or manual gives the exact figure; these are typical values:
| LED bulb | 9-12 W |
| Ceiling fan (regular / BLDC) | 50-75 W / 28-35 W |
| Wi-Fi router | 10 W |
| Laptop | 50-65 W |
| LED TV | 60-120 W |
| Refrigerator | 150-250 W (much higher for a moment at start-up) |
| 1 HP water pump | about 750 W |
| 1.5 ton inverter AC | 1,200-1,800 W |
Add them up. That total is your running load.
Step 2: Add headroom for surges
Motors - in fridges, pumps, ACs and mixers - draw several times their running power for a second when they start. Two rules keep you safe:
- Choose an inverter whose rated output is at least 25% above your running load.
- Check that its peak power covers the start-up surge. Every PowerRun hybrid inverter has a peak rating of twice its rated output - 7,200 VA on the 3.6 kW model, for example.
Step 3: Match the battery voltage
Inverters are built for a fixed battery voltage, and the battery has to match:
- 24 V inverters - PowerRun 3.6 kW and 4.2 kW - use 25.6 V lithium batteries.
- 48 V inverters - PowerRun 6.2 kW, 8.2 kW, 11 kW and 12 kW - use 51.2 V lithium batteries.
Higher voltage means lower current for the same power, so larger systems run on 48 V.
Worked examples
A typical 2-3 BHK without AC on backup
10 LED bulbs (100 W) + 5 fans (300 W) + fridge (200 W) + TV (100 W) + router and laptop (75 W) = 775 W. With 25% headroom that is under 1 kW, so the 3.6 kW hybrid inverter handles it with plenty of room to add an AC later.
The same home with one 1.5 ton AC
775 W + 1,500 W = 2,275 W running, about 2.85 kW with headroom - still within the 3.6 kW model. If you want the AC and a water pump together, look at the 4.2 kW.
A larger home with two ACs and a pump
775 W + 3,000 W + 750 W = 4,525 W, or about 5.7 kW with headroom. That points to the 6.2 kW model on a 48 V battery bank.
Don't forget the solar side
A hybrid inverter also has a limit on how much solar it can take. The 3.6 kW model accepts up to 5,000 W of panels; the 11 kW and 12 kW models accept 2 x 8,500 W across two MPPT inputs. If you plan a large rooftop array, check this number before you buy - our guide on how many solar panels you need walks through it.
Planning to grow?
The 8.2 kW, 11 kW and 12 kW models support parallel operation, so a business can start with one unit and add a second later instead of replacing the first.
Still not sure?
Send us your appliance list on WhatsApp and our team will suggest the right inverter and battery. You can also try the battery calculator to size the battery for the backup hours you need.