Well Pump Horsepower: What Size Do You Need?

Factors That Determine HP Needs

1. Well Depth (Vertical Lift)

The most important factor. Pump must lift water from the pumping level to the surface. Deeper wells require more power.

• Static water level: Where water sits at rest
• Drawdown: How far it drops during pumping
• Pumping level: Static level + drawdown = total lift needed

2. Flow Rate (GPM)

Higher GPM requires more HP. Peak household demand determines minimum GPM.

• 1-2 people: 5-8 GPM
• 3-4 people: 8-12 GPM
• 5+ people: 12-20 GPM
• Add for irrigation, livestock, etc.

3. Pressure Requirements

Higher pressure needs (40/60 or 50/70 settings) require more HP than standard 30/50.

4. Horizontal Distance

Long runs from well to house add friction loss. Every 100 feet horizontal ≈ 1 foot of head.

HP Selection Chart

Based on Depth and Flow

Note: This is a general guide. Actual sizing should consider specific well characteristics and pump curves.

How to Calculate Pump Size

Step 1: Determine Total Dynamic Head (TDH)

TDH = Pumping Level + Pressure + Friction Losses

• Example:
• Pumping level: 180 feet
• Pressure needed: 50 PSI = 115 feet equivalent
• Friction losses: ~15 feet
• TDH = 180 + 115 + 15 = 310 feet

Step 2: Determine GPM Needed

• Count fixtures × 1 GPM (rough estimate)
• Or calculate peak demand scenarios
• Don't forget irrigation if applicable

Step 3: Use Pump Performance Curves

Every pump has a performance curve showing GPM at various TDH values. Select a pump that delivers your GPM at your TDH within its efficiency range.

Let Professionals Size It

Proper pump sizing requires knowing your specific well characteristics. A professional can test your well and size the pump correctly.

Pump Types by HP Range

1/2 HP Pumps

• Shallow wells (under 100 feet)
• Low demand applications
• Small cabins or supplemental use
• Cost: $200-$400

3/4 HP Pumps

• Medium depth wells (100-200 feet)
• Most common residential size
• Average household demand
• Cost: $300-$500

1 HP Pumps

• Deeper wells (150-250 feet)
• Higher flow requirements
• Larger homes
• Cost: $400-$700

1.5-2 HP Pumps

• Deep wells (250-400 feet)
• High demand or irrigation
• Multi-family or commercial
• Cost: $600-$1,200

3+ HP Pumps

• Very deep wells (400+ feet)
• Agricultural applications
• High volume needs
• Cost: $1,000-$2,500+

Common Sizing Mistakes

Oversizing

• Wastes electricity
• May outrun well's production
• Causes rapid cycling
• Shortens pump life

Undersizing

• Can't meet peak demand
• Runs continuously
• Overheats and fails early
• Poor pressure upstairs

Ignoring Well Yield

A 20 GPM pump in a 5 GPM well will just pump it dry. The pump must be matched to what the well can produce, not just what you want.

Forgetting About Drawdown

Static water level isn't enough—you need to know pumping level after sustained pumping.

We service all major pump brands including Franklin Electric, Grundfos, Goulds (Xylem), and Sta-Rite (Pentair). Our trucks carry common parts and components for same-day repairs.

Frequently Asked Questions

What size well pump do I need?

Depends on depth and flow needs. For a typical 150-foot well serving an average home, 3/4 to 1 HP works well. Use the chart above as a guide.

Can I put a bigger pump in my well?

You can, but bigger isn't always better. Match the pump to your well's yield and your needs. Oversized pumps waste energy and may cause problems.

How do I know my current pump's HP?

Check the nameplate on the pump motor (if visible), the breaker size (gives clue), or the pump documentation. A professional can identify it during service.

Does a bigger pump mean more water?

No—the well produces what it produces. A bigger pump just extracts it faster. If you have low yield, you need storage, not a bigger pump.

What's the most common residential pump size?

3/4 HP is most common, followed by 1 HP. These handle most typical residential situations.