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A LED Tube Light draws about 20W, so a 150Ah 12V tubular battery runs one of them for roughly 31 hours 30 minutes on its own. That comes from 630Wh usable energy divided by 20W. A 2-foot or 4-foot LED batten, the standard replacement for fluorescent tubes.
A 2-foot or 4-foot LED batten, the standard replacement for fluorescent tubes. The 20W figure used across this page is a typical mid-range Indian retail unit — check the nameplate on yours and put the real number into the calculator, because a 10W difference on an appliance you run for six hours is 60Wh out of a budget of only a few hundred.
Category: Lighting. People search for this as led batten, tube light watts, 20w batten — all the same question, and all answered by the same arithmetic.
Usable energy is Ah x 12V x 0.7 efficiency x 0.5 depth of discharge. Divide that by the appliance draw and you have the runtime with nothing else connected.
| Battery | Usable energy | Runtime with one unit | Runtime with two |
|---|---|---|---|
| 100Ah | 420Wh | 21 hours | 10 hours 30 minutes |
| 120Ah | 504Wh | 25 hours 12 minutes | 12 hours 36 minutes |
| 135Ah | 567Wh | 28 hours 21 minutes | 14 hours 11 minutes |
| 150Ah | 630Wh | 31 hours 30 minutes | 15 hours 45 minutes |
| 165Ah | 693Wh | 34 hours 39 minutes | 17 hours 19 minutes |
| 180Ah | 756Wh | 37 hours 48 minutes | 18 hours 54 minutes |
| 200Ah | 840Wh | 42 hours | 21 hours |
| 220Ah | 924Wh | 46 hours 12 minutes | 23 hours 6 minutes |
| 250Ah | 1050Wh | 52 hours 30 minutes | 26 hours 15 minutes |
Nothing stops you connecting more units — the limit is runtime, not the inverter, until you hit the surge ceiling below.
| Quantity | Continuous draw | Runtime | Band |
|---|---|---|---|
| 1 | 20W | 31 hours 30 minutes | Low load |
| 2 | 40W | 15 hours 45 minutes | Low load |
| 3 | 60W | 10 hours 30 minutes | Low load |
| 4 | 80W | 7 hours 53 minutes | Low load |
| 5 | 100W | 6 hours 18 minutes | Low load |
| 6 | 120W | 5 hours 15 minutes | Low load |
Very few appliances run flat out for a full hour. A fridge compressor cycles, a mixer runs in bursts, a pump fills a tank and stops. Battery Buddy asks for minutes run per hour and multiplies the wattage by that fraction — which is why its answers are usually longer, and more honest, than a calculator that assumes continuous draw.
| Minutes run per hour | Average hourly draw | Runtime on a 150Ah battery |
|---|---|---|
| 15 min | 5W | 126 hours |
| 30 min | 10W | 63 hours |
| 40 min | 13.3W | 47 hours 15 minutes |
| 45 min | 15W | 42 hours |
| 60 min | 20W | 31 hours 30 minutes |
This is a surge-sensitive appliance. Battery Buddy applies a 1.5x start-up multiplier to a LED Tube Light, so one unit spikes to about 30W for a second or two at switch-on. Your inverter has to survive everything else already running plus that spike — not just the average load.
Peak demand = total continuous load + the single largest start-up surge. The sizing advisor runs that check automatically for whatever mix you enter.
These are complete household and shop profiles we model, each with its own worked page.
| Profile | Average draw | Backup on a 150Ah battery |
|---|---|---|
| 4 tube lights + 2 fans + billing computer | 420W | 1 hour 30 minutes |
About 20W while running. A 2-foot or 4-foot LED batten, the standard replacement for fluorescent tubes. Always confirm against the nameplate rating on your own unit before sizing a battery around it.
Roughly 31 hours 30 minutes with nothing else connected: 630Wh usable divided by 20W. Add anything else to the inverter and that time drops proportionally.
Battery Buddy applies a 1.5x multiplier, so a single unit peaks near 30W at switch-on before settling to 20W. That spike, not the running load, is what trips undersized inverters.
Yes — one unit runs about 21 hours on a 100Ah 12V battery at 70% efficiency. Whether that is enough depends on how long your outages actually last and what else shares the inverter.
The figures assume 70% system efficiency. An older battery, low electrolyte, corroded terminals or thin cabling all reduce the effective factor. Measure yours with the efficiency estimator and re-run the numbers — it takes one discharge test.
Battery Buddy is free, needs no sign-up, sells no batteries and shows every formula it uses. It is built by Flocci Technologies, an India-first AI-native software studio behind 30+ apps that share one Flocci identity.