Tank Filling Time Calculator
Find out how long your pump takes to fill a water tank, and the electricity it uses each time.
Inputs
Formula
- Volume to fill = capacity × (1 − current level)
- Time = volume ÷ flow
- Energy = HP × 0.746 ÷ motor efficiency × hours
Filling time is just the volume left to fill divided by the pump's flow. Knowing it lets you set a timer instead of overflowing the tank. The energy cost uses 0.746 kW per HP and a typical 70% motor efficiency for small pumps.
Step-by-step calculation
- 1
Volume
capacity × (1 − level)
800 L
- 2
Time
volume ÷ flow
13.33 min
- 3
Energy
kW × hours
0.237 units
Worked example
- 1A 1,000 litre tank that is 20% full needs 800 litres.
- 2At 60 lpm that takes 800 ÷ 60 = 13.3 minutes.
- 3A 1 HP pump draws about 1.07 kW → 0.24 units → ₹1.90 per fill.
Tips
- Fit an automatic level controller — it pays for itself in wasted water and power.
- Fill at night when the supply pressure is highest and the tariff may be lower.
Frequently asked questions
How long does a 1000 litre tank take to fill?
About 15–20 minutes with a typical 1 HP domestic pump delivering 50–70 lpm.
Does the tank height change the time?
Yes — greater lift reduces the flow, so a rooftop tank fills more slowly than a ground tank.
How much electricity does one fill use?
Around 0.2–0.4 units for a 1,000 litre tank with a 1 HP pump.
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