What Size Generator for a Sump Pump?

A sump pump is the highest-value load in this entire site relative to the watts it needs. If you have one, your basement floods without it, and a flooded basement during a storm is routinely the most expensive single consequence of a power outage. It costs about a thousand watts to prevent.

The published figures, and what the jump between them tells you

EWEB lists both common residential sizes, which is useful because it shows how the numbers scale:

Check which you have — it is printed on the pump housing. The difference between 1,300 and 2,200 watts of surge can be the difference between a small inverter generator working and tripping.

In a realistic plan

3,450 running watts with 4,950 starting watts. That is a 3,500-4,000 running-watt inverter generator at the quiet end, or a mid-sized dual fuel machine if you want headroom to add a well pump later.

The thing specific to sump pumps: duty cycle

A sump pump does not run continuously. It runs when the pit fills, which in a serious storm might be every few minutes and in ordinary weather might be not at all. That has two consequences worth planning around.

First, average draw is far below running watts, which makes a battery more viable than the raw numbers suggest — right up against the second consequence, which is that the surge still has to be available every single time it cycles. A battery that can supply 2,200 watts of surge will run a sump pump for a long time on modest capacity. A battery that cannot supply the surge will not run it at all, regardless of capacity.

Second, it cycles unpredictably, which means you cannot be standing there managing load. If you are using an interlock kit rather than a transfer switch, the sump pump circuit needs to stay on and you need headroom reserved for it — not borrowed for the microwave at the moment the pit fills.

The dedicated-battery alternative worth knowing about

There is a whole product category of battery backup units built specifically for sump pumps — a deep-cycle battery and a DC pump or inverter, wired into the pit, that take over automatically. They are cheaper than a generator, fully automatic, and need nobody at home.

We do not cover them on this site because they are a plumbing product rather than a portable power one, and we would rather say that plainly than pretend our category is the only answer. If the sump pump is your only backup concern, that is the product to research, and a generator is probably more machine than you need.

If the sump pump is one of several concerns — and if you also want heat, a fridge and water — then a generator that covers all of them is the better buy, and the pump is the cheapest thing on the list.

The short answer

Picks that cover a sump pump and the rest of the essentials

#	Product	Best for	Score	Price
1	WEN DF8000X 8,000W Dual Fuel The best-value correctly-sized home backup generator here: enough for every essential circuit, dual fuel, CO shutoff, a real transfer-switch outlet, and no money spent on capacity you will not use.	Essential circuits, dual fuel, lowest cost	8.5/10★★★★★	$623.17
2	Champion 4,500W RV Ready Inverter The best balance of quiet, clean power and real output for cord-based backup: enough for the essentials, under 3% THD, half the price of the Honda equivalent.	Quiet backup at a sane price	8.5/10★★★★★	$674.10
3	Jackery Explorer 2000 v2 The most sensible battery backup for most homes: enough capacity to carry a fridge and electronics through a typical outage, indoors, silently.	The default 2 kWh home backup battery	8.9/10★★★★★	$898.99

#ad Prices as of October 5, 2026; they may have changed since. Scores are our editorial judgment from published specifications, not test results — how we pick. How we are funded.

Note the hard-wiring issue: a sump pump is often on a dedicated circuit, and if it is hard-wired you cannot reach it with a cord. See connecting a generator to your house. If yours is plugged into a receptacle in the pit, a cord from a generator will work — which makes it one of the few critical loads you can cover without an electrician.