Battery capacity is measured in kilowatt-hours (kWh) — the amount of energy stored. Appliance draw is measured in watts (W) or kilowatts (kW) — the rate of energy consumption. Runtime is simple division:
Two adjustments to apply to that simple formula:
- Usable capacity is less than nameplate. For LFP batteries, usable capacity is ~90% of nameplate. So a 5 kWh LFP battery delivers ~4.5 kWh of usable energy per cycle.
- Inverter efficiency. Quality hybrid inverters convert DC battery power to household AC at 95–97% efficiency. Budget inverters can drop to 88%.
How much do common Indian home appliances draw?
| Appliance | Typical draw (watts) | Notes |
|---|---|---|
| LED bulb | 9–15 W | Per bulb |
| Ceiling fan | 50–75 W | BLDC fans are lower (28–35 W) |
| Refrigerator (4-star, 250 L) | 120–180 W average | Compressor cycles on/off; peak ~600 W on startup |
| Wi-Fi router | 5–15 W | Plus modem ~10 W |
| Television (43" LED) | 60–100 W | OLED slightly higher |
| Laptop charging | 45–90 W | Gaming laptops up to 200 W |
| Phone charger | 10–25 W | Per phone |
| Mixer / juicer | 500–800 W | Short bursts of a few minutes |
| Microwave | 800–1,200 W | Used briefly |
| Geyser (15 L instant) | 2,000–3,000 W | Heavy load; consider whether to back up |
| Iron | 1,000–1,500 W | Heavy; short bursts |
| Air conditioner — 1.0 ton inverter | 800–1,100 W average | 1.5–2× this during high-cooling demand |
| Air conditioner — 1.5 ton inverter | 1,200–1,600 W average | Lower on inverter compressor; non-inverter 2× this |
| Air conditioner — 2.0 ton inverter | 1,600–2,200 W average | Heavy on the battery |
| EV charger (Level 1 / 3-pin) | 1,800–3,000 W | Not usually backed up; runs from grid |
Worked examples
Example 1: 5 kWh Powerten Raksha — apartment / 2 BHK
Suppose the grid drops at 7 pm. Typical evening load in a 2 BHK: 5 LED bulbs (60 W), 2 ceiling fans (100 W), refrigerator (150 W average), Wi-Fi (15 W), TV on intermittently (80 W), one phone charging (15 W) = ~420 W steady draw.
Runtime: 4.5 usable kWh ÷ 0.42 kW = ~10.7 hours. The battery comfortably runs the home through the night and into the morning.
Add a 1.5-ton inverter AC running at average 1,300 W: total load 1,720 W. Runtime: 4.5 kWh ÷ 1.72 kW = ~2.6 hours. AC drains a small battery fast — which is why most 5 kWh users run AC for an hour or two, not all night.
Example 2: 16 kWh Powerten Raksha — 3 BHK / villa
Same 2 BHK base load (420 W) but in a larger home with two ACs running:
- Base load: 420 W
- 1.5-ton inverter AC #1 (master bedroom): 1,300 W
- 1.5-ton inverter AC #2 (living room): 1,300 W
- Total: ~3,020 W
Usable: 14.4 kWh. Runtime: 14.4 ÷ 3.02 = ~4.8 hours. Enough to cover the entire late-evening / sleep window with both ACs running. Reduce to one AC overnight and you get 9–10 hours.
Example 3: Selective backup — what really matters
Most Indian homes don't need every circuit backed up. Critical load list:
- Lights and fans throughout
- Refrigerator
- Wi-Fi router + modem
- One TV / entertainment
- Phone charging
- One AC (master bedroom)
Skip from backup: water geyser, iron, EV charger, second AC, kitchen appliances on standby. This load profile averages 600–1,800 W depending on AC use, and a 5 kWh battery handles 3–7 hours of typical evening backup.
Why your real runtime might differ
- Compressor surges. Older fridges and non-inverter ACs spike 2–3x their average draw on startup. Inverters need to handle this; mid-tier hybrid inverters generally do, budget ones sometimes trip.
- Temperature. Lithium batteries deliver slightly less capacity at temperatures above 35°C or below 15°C. In an Indian summer, expect maybe 5–8% derating in unconditioned utility rooms.
- State of health. A 7-year-old battery delivers ~85% of its original usable kWh. Plan for capacity loss when sizing.
- Phantom loads. Set-top boxes, smart TVs in standby, always-on water purifiers, and chargers left plugged in collectively pull 20–60 W around the clock. Over 8 hours that's 0.5 kWh — significant on a small battery.
A simple sizing rule
For an Indian home that wants:
- 3 hours of essential backup (lights, fan, fridge, Wi-Fi): 2.5–3 kWh
- Evening + overnight essential backup: 5 kWh
- Whole-home backup including one AC for several hours: 10 kWh
- Multi-AC villa, full-day backup: 16 kWh
Going larger than necessary is rarely wasted — it gives headroom for future loads (EV, additional AC, growing family). Going smaller almost always causes regret.
Use the calculator
Plug your actual numbers into the Powerten savings calculator — it estimates runtime based on your electricity bill profile and proposed system. Or book a home consultation and we'll work out the right capacity from your last twelve months of bills.
The bottom line
A 5 kWh LFP battery runs typical Indian evening loads (lights, fans, fridge, Wi-Fi, TV) for 10+ hours — and a single AC for around 2.5 hours. A 16 kWh battery runs a multi-AC home for 4–5 hours of peak use, or 10–15 hours of moderate use. The key is to be honest about what you actually want to power, then size the battery to match — with some headroom for the next decade.