Most submersible pump problems start at the counter, not in the borewell. Buyers often pick a pump by asking “my neighbour uses 1 HP, so I will too”, without checking how deep their water is or how high it has to go. The result is either a weak pump that cannot fill the tank, or an oversized one that wastes electricity and can run the borewell dry. This guide shows how to work out the right HP in three steps, with ready tables for homes, buildings and farms.
1. The Three Things That Decide Pump HP
Total head (in metres)
Total head is the full height the pump has to push water. It has three parts: the depth of the water level in the borewell (not the borewell’s total depth), the height from ground to your overhead tank, and friction loss in pipes and bends. A simple rule is to add 10% to 15% of the vertical height for friction in a normal home setup.
Flow rate (litres per minute, LPM)
Flow rate is how much water you need per minute. For homes, it depends on how fast you want the tank to fill. A 1,000-litre tank filled in about 25 minutes needs 40 LPM. Farms are sized on irrigation area and hours of supply, which usually means 100 LPM or more.
Pumpset efficiency
No pump turns all its electricity into water lift. The combined efficiency of pump and motor in small borewell pumpsets is often in the 35% to 50% range. In this guide we use 40% to keep the estimate on the safe side.
2. The HP Formula (Simple Version)
The number 4,560 converts litres per minute and metres into horsepower. Using 40% efficiency (0.40), the formula becomes: HP = (LPM × Head) ÷ 1,824. After you get the result, add about 20% as a safety margin and round up to the next standard pump size (0.5, 1, 1.5, 2, 3 or 5 HP).
3. Ready Reckoner: HP by Total Head (Homes)
This table assumes a household flow of about 40 LPM, 40% pumpset efficiency and a 20% safety margin.
| Total head | Recommended HP | Typical situation |
|---|---|---|
| Up to ~20 m | 0.5 HP | Shallow water level, single-storey house, sump to roof tank |
| 20–38 m | 1 HP | Most urban and semi-urban homes with moderate water levels |
| 38–57 m | 1.5 HP | Deeper water level or 2–3 storey house |
| 57–76 m | 2 HP | Deep borewells in water-stressed areas |
| 76–110 m | 3 HP | Very deep water levels; check borewell size and phase supply |
Indicative only. Actual performance varies by brand, number of stages and pipe size; check the head-flow chart on the pump’s datasheet before buying.
4. HP for Buildings and Farms (Higher Flow)
| Use case | Flow | Total head | Calculated HP (+20%) | Choose |
|---|---|---|---|---|
| Small apartment / 4–6 flats | ~100 LPM | ~40 m | ~2.6 | 3 HP |
| Small farm irrigation | ~150 LPM | ~50 m | ~4.9 | 5 HP |
| Kitchen garden / nursery | ~60 LPM | ~30 m | ~1.2 | 1.5 HP |
Above about 2 HP, many pumps are offered in three-phase versions, and larger HP pumps often need a 6-inch borewell rather than a 4-inch one. Confirm your electricity connection and borewell diameter with the supplier before ordering.
5. Worked Example: Choosing a Pump for a 2-Storey House
Worked model: family of 5, water level at 35 m
- Daily water need: 5 people × 135 litres = 675 litres, round up to about 700 litres per day.
- Total head: 35 m water level + 8 m to the roof tank = 43 m; add about 15% for friction = about 50 m.
- Flow target: fill a 1,000-litre tank in about 25 minutes = 40 LPM.
- HP calculation: (40 × 50) ÷ 1,824 = about 1.1 HP. Add 20% margin = about 1.3 HP.
- Choose: 1.5 HP pump.
- Running cost: about 18 minutes a day to pump 700 litres. At roughly 1.5 kW drawn, that is about 13 units a month, or around ₹100–110 a month at ₹8 per unit.
All figures are approximate. Electricity tariffs vary by state, and actual consumption depends on the pump model and water level changes across seasons.
6. 1 HP vs 1.5 HP: Which Is Better?
| Factor | 1 HP | 1.5 HP |
|---|---|---|
| Suitable total head (at ~40 LPM) | Up to about 38 m | About 38–57 m |
| Power drawn | Lower | About 50% higher |
| Best for | Moderate water levels, 1–2 storey homes | Deeper water levels or taller homes |
| Risk if wrongly chosen | Slow or no flow when water level drops in summer | Wasted power, dry running in low-yield borewells |
If your water level drops sharply in summer, size the pump on the summer level, not the monsoon level. A pump that works in August may struggle in May.
7. Common Mistakes to Avoid
Using borewell depth instead of water level. A 90 m borewell with water at 30 m needs a pump sized for about 30 m plus tank height and friction, not 90 m.
Oversizing “just to be safe”. A pump far bigger than needed can pull water faster than a low-yield borewell refills, which leads to dry running and motor damage.
Ignoring cable size and control panel. Long cable runs need the correct cable size to avoid voltage drop. Use a proper starter or control panel with dry-run protection.
Skipping certification. Look for the ISI mark under IS 8034 for borewell submersible pumpsets, and BEE star-labelled models where available.
Key Takeaways
- HP depends on total head, flow rate and efficiency, not on borewell depth alone.
- Use HP = (LPM × Head) ÷ 1,824, then add about 20% and round up.
- Most homes need 0.5 to 2 HP; buildings and farms usually need 3 to 5 HP.
- Size for the summer water level and confirm with the manufacturer’s pump curve.
Related reading: Submersible Pump Price List 2026 (Brand & HP-wise) · Top Submersible Pump Brands in India
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Disclaimer: Calculations in this guide are indicative estimates for selection purposes only. Final pump selection should be confirmed with the manufacturer’s performance chart and a qualified installer.
