72-hour backup power without the math headache

How much backup power do I need for a 3-day outage?

For three days, the important question is not just how big a battery to buy. It is what needs to stay running and how you will recharge the battery after the first day.

The short answer

Food only: a roughly 2 kWh power station is a practical starting point, but three full days may still require recharging depending on your refrigerator, freezer and conditions.

Food + Wi-Fi + lights: start around 2 kWh and include a recharge plan from the beginning.

More household essentials: look at expandable systems rather than expecting one portable battery to carry an entire house for 72 hours.

Pick the situation that sounds like your house

Keep the food cold

Refrigerator and/or freezer are the priority. Phones can be charged occasionally.

Start around 2 kWh

Food + Wi-Fi + lights

You also want the router, phones and a few efficient lights available.

2 kWh + a recharge plan

Keep life more normal

You want to add several household essentials and have more room for changing needs.

Choose expandable capacity

Why there is no honest universal “72-hour battery”: refrigerators and freezers cycle on and off, and their consumption changes with the appliance, room temperature, door openings and other conditions. By day two or three, recharging matters as much as battery size.

Three sensible starting points

Jackery Explorer 2000 v2

A straightforward 2 kWh starting point. Jackery specifically positions this unit for essentials such as a refrigerator, Wi-Fi and lights during an all-day outage.

2,042Wh capacity • 2,200W AC output • 4,400W surge • about 39.5 lb • LiFePO₄

See current Jackery details

BLUETTI AC200L

Better when expansion and solar charging matter. The base battery is about 2 kWh, and BLUETTI supports compatible expansion batteries and up to 1,200W solar input.

2,048Wh capacity • 2,400W AC output • expandable • up to 1,200W solar input • LiFePO₄

See current BLUETTI details

EcoFlow DELTA 3 Plus

Smaller and easier to move when you expect to recharge. Its 1,024Wh base capacity is not the first choice for trying to coast through three days, but the system supports an extra battery and multiple recharge methods.

1,024Wh capacity • 1,800W AC output • 3,600W surge • 5-year warranty

See current EcoFlow details

The part people miss: recharging

Decide what absolutely has to stay on. Food refrigeration usually comes before convenience appliances.

Buy enough battery to cover the vulnerable periods. Bigger capacity buys time, but it also gets expensive and heavy quickly.

Give yourself a way to refill it. Solar, a compatible generator, vehicle charging or restored grid power can turn a battery from a one-shot reserve into a repeatable system.

Solar ratings are maximums under suitable conditions, not guaranteed real-world output. Clouds, shade, panel angle, season and available daylight all matter.

If you only care about the refrigerator and freezer

You may not need a full 72-hour system. Start with the refrigerator and freezer backup-power guide and size around those actual loads first.