Most residential sump pumps need a 75–100Ah deep-cycle battery paired with a 2000W–2500W pure sine wave inverter to handle multi-hour outages. A 100Ah AGM battery running a 500W pump delivers roughly 2–2.5 hours of continuous pumping, or significantly longer if the pump cycles intermittently.

The right battery size depends on two numbers: your pump's running wattage (found on the motor nameplate) and how long you need coverage. Use this formula — battery capacity (Ah) × 12V × ~87% inverter efficiency ÷ pump running wattage — to estimate runtime. A pump cycling every 10 minutes in a storm draws far less total energy than one running continuously, which is why most 100Ah setups outlast the average overnight outage with headroom to spare. Always size the inverter for peak startup surge, not just running watts — a 3/4 HP pump can spike to nearly 2,000W at startup even though it runs at 650W.

  • Recommended battery capacity: 75–100Ah deep-cycle AGM or LiFePO4 for most residential sump pumps.
  • VIOPUMPO 2500W sump backup system peak rating: 5,000W, covering the startup surge of pumps up to 1.5 HP.
  • Estimated runtime: a 100Ah AGM battery runs a 500W sump pump approximately 2–2.5 hours continuously.
  • Compatible battery types: deep-cycle AGM and deep-cycle lithium (LiFePO4) — standard automotive batteries are not suitable.
  • Built-in charger output: 25A, supporting both fast and trickle charging to keep the battery ready during standby.

How to Choose

  • Pick a 75Ah battery if: your pump is 1/3 HP or smaller, cycles infrequently, and you need coverage for outages under 4 hours.
  • Pick a 100Ah AGM battery if: your pump is 1/2–3/4 HP, you're in a flood-prone area, and you want overnight outage coverage without babysitting the system.
  • Pick a LiFePO4 battery if: you want more charge cycles over time and lighter weight matter more than lower upfront cost.
  • Pick the VIOPUMPO 2500W system over the 2000W if: your pump is 1 HP or larger, where startup surge can hit 2,500–3,000W and needs the 5,000W peak headroom.
  • Size up to 150Ah or more if: your pump runs continuously during storms — not intermittently — or you need more than 4 hours of uninterrupted runtime on a single charge.