Sump pump sizing Last reviewed June 30, 2026
1/3 HP vs 1/2 HP Sump Pump: Which Size Do You Need?
By the WhatSize editorial team 4 min read Standards-reviewed
TL;DR
Choose 1/3 HP for light seepage in small pits. Choose 1/2 HP for most residential basements — it handles 20% more water and costs only $30-40 more.
Looking for a different size?
See What Size Sump Pump for a Basement? Complete Guide
or browse all sump pump sizing guides.
The $30 Difference Between 1/3 HP and 1/2 HP
A 1/3 HP pump handles about 3,000 GPH while a 1/2 HP handles 3,600 GPH — 20% more capacity. The difference is $30-40 upfront. For most homeowners, the 1/2 HP is the smarter investment.
Top picks for this size
WAYNE CDU800 1/2 HP Submersible Sump Pump – Cast Iron & Stainless Steel, Vertical Float Switch, 5,100 GPH, 3-Year Warranty #ad
★★★★ 4.4 · 1K+ · $159
Liberty Pumps 287 1/2-Horse Power 1-1/2-Inch Discharge 280-Series Automatic Submersible Sump Pump with VMF Switch #ad
★★★★☆ 4.5 · 247+ · $312
Zoeller M98 Flow-Mate Sump Pump - 1/2 HP - Cast Iron - LED Power Plug - High Flow - Vortex Impeller - Stainless Steel Hardware - Factory Tested and Float Operated - Submersible Sump Pump - 115V #ad
★★★★☆ 4.6 · 1K+ · $304
Zoeller Waste-Mate 267 Sewage Pump, 1/2 HP – Heavy-Duty Submersible Sewage, Effluent or Dewatering Pump #ad
★★★★ 4.4 · 130+ · $412
Liberty Pumps P382LE51 1/2-Horse Power 24 by 24-Inch Pro380 Series Simplex Sewage System #ad
★★★★☆ 4.5 · 210+ · $700
Liberty Pumps 457-2 Vertical Magnetic Float 1/2 HP Submersible Sump Pump, BLACK #ad
★★★★ 4.4 · 57 · $257
Liberty Pumps 405 Commercial 1/2 HP Drain Pump, Metal Plastic #ad
★★★★☆ 4.5 · 142+ · $465
Zoeller Waste-Mate 267-0001 Sewage Pump, 1/2 HP Automatic – Heavy-Duty Submersible Sewage, Effluent or Dewatering Pump #ad
★★★★ 4.4 · 948+ · $462
Liberty Pumps 457-2 450-Series 1/2 hp Submersible Sump Pump #ad
★★★★ 4.4 · · $281
Zoeller M98 Flow-Mate Sump Pump - 1/2 HP - Cast Iron - LED Power Plug - High Flow - Vortex Impeller - Stainless Steel Hardware - Factory Tested and Float Operated - Submersible Sump Pump - 115V #ad
★★★★☆ 4.6 · 160+ · $350
Superior Pump 91570 3300GPH Thermoplastic Submersible Utility Pump with 10-Foot Cord, 1/2 HP #ad
★★★★ 4.3 · 2K+ · $112
WAYNE - 1/2 HP Sump Pump with Integrated Vertical Float Switch and 12 Volt Battery Back Up Capability, Battery Not Included - Up to 5,100 Gallons Per Hour - Heavy Duty Basement Sump Pump System #ad
★★★★☆ 4.5 · 826+ · $570
AQUASTRONG 1/2 HP Sump Pump, 3450 GPH Stainless Steel and Thermoplastic Submersible Water Pump, Automatic Float Switch with Piggy-back Plug,1-1/2" NPT Discharge Subpumps for Basement and Flooding Area #ad
★★★★ 4.4 · 78 · $120
Westinghouse Battery Backup Sump Pump System – 1/2 HP Dual Sump Pumps with Automatic Switchover, Stainless Steel Construction, Top Suction Design, Basement Flood Protection #ad
★★★★☆ 4.5 · 49 · $570
Rainbro 1/2 HP Thermoplastic Submersible Sump Pump With Vertical Float Switch, Utility Pump, Model# PSU051V #ad
★★★★ 4.2 · 228+ · $90
LANCHEZ 1/2 HP 5200 GPH Submersible Sump Pump Cast Iron and Stainless Steel with Integrated Vertical Float Switch, Sewage/Effluent Pump for Basement, Basin, Sewage System, 1-1/2" NPT Discharge #ad
★★★★ 4.4 · 108+ · $126
Westinghouse Sump Pump 1/2 HP 69 GPM Submersible Water Pump Automatic Vertical Float Switch Heavy Duty Basement Crawl Space Flood Removal Pump High Flow Water Drainage #ad
★★★★ 4.4 · 95 · $110
Superior Pump 92057 1/2 HP Thermoplastic Submersible Sump Pump with Vertical Float Switch, plus 1-1/2-Inch Rubber Boot Check Valve #ad
★★★★ 4.4 · 3 · $160
These Amazon-available picks meet the calculated spec. For region-specific or licensed contractor-installed options, consult a local professional. See our Disclaimers.
Decision Guide
- Choose 1/3 HP if: pit under 24", light seepage, tight budget ($69-89)
- Choose 1/2 HP if: typical basement, pit 18-36", moderate to heavy water
- Choose 3/4 HP if: pit over 36", heavy water, or previous pump failed
Frequently asked questions
Should I get a 1/3 HP or 1/2 HP sump pump?
Yes, as long as the discharge pipe size matches (typically 1.5"). It's a straightforward upgrade.
Does a larger HP pump use more electricity?
Very little — a 1/2 HP uses about 250W more than a 1/3 HP while running. Annual cost difference is about $5-15.
You might also need
More sump pump sizing guides
- What Size Sump Pump for a Basement? Complete Guide
- Sump Pump Sizing for Heavy Rain Areas
- Sump Pump Battery Backup: What Size Do You Need?
- Sump Pump Installation Guide: Pipe Size, Check Valves & More
- Sump Pump GPH Chart: Capacity by Horsepower & Lift
- Sump Pump Battery Backup Sizing + Runtime Chart
- What Size Sump Pump for a Crawl Space?
- 1/2 HP vs 3/4 HP Sump Pump: Which Do You Need?
- What Size Sump Pump for a High Water Table?
Still choosing between sizes? Compare: 1/3 vs 1/2 HP