Sump pump sizing Last reviewed June 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
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.
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
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.