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GreenCommuteGuide

Calculators and sizing tools

Work out what size you need from what you actually own, not from a marketing chart.

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What size do you actually need?

Tick what you want to keep running. Set how long. You'll get a number and three units that can genuinely do it.

Choose your appliances

Essentials

  • Practically free. Never the thing that drains your battery.

  • Only useful if your ISP still has power at their end.

    12 hr

  • Covers two phones plus one laptop charging on and off.

    6 hr

Kitchen

  • Compressor cycles on and off. Keep the door shut and it works less.

    12 hr

  • Dorm-size. Cheap to run, easy on a small battery.

  • A full freezer holds cold for a day on its own. You may not need to power it constantly.

  • Huge draw, tiny runtime. Fine in short bursts, brutal if you cook a meal.

  • The heating element is the whole cost. Ten minutes, then done.

Comfort

  • Cheaper than people expect. Morale matters in a long outage.

  • The efficient way to survive a summer outage. AC is not.

  • Be honest with yourself: almost no portable battery can do this overnight.

  • If you have gas heat, powering just the blower keeps the whole house warm.

  • The surge at startup is what trips small units, not the running draw.

  • Needs a serious unit. Check the surge rating, not the running rating.

Medical

  • Turn the heated humidifier OFF and a CPAP becomes trivially cheap to run.

  • The heater roughly doubles the draw. Dry throat beats a dead battery.

  • Life-critical. Size for double what you calculate and talk to your equipment supplier.

Water & Sump

  • Runs in short bursts, but the startup surge is enormous. Many units cannot start it at all.

  • Duty cycle depends entirely on how much water is coming in. In a storm, assume worse.

1 day

Most US outages end within a day. If you're in hurricane or ice-storm country, plan for three and hope for one.

You need about

1,385Wh

That's 1,065 Wh of actual use, plus 30% headroom so you're not running the pack flat.

This assumes everything runs for the full time with no rationing. In a real outage most people cycle the fridge and turn things off, which stretches a smaller unit a long way.

Biggest startup surge
900W
If everything runs at once
235W

The surge number matters more than people think. A unit that can't start your fridge compressor is useless, however big its battery is.

These three can do it

  • Smallest that fits

    Jackery Explorer 2000 Plus

    2,042 Wh · 3,000W · 61.5 lb

    Jackery's serious one. Stack batteries onto it and it grows with your paranoia.

    Link not set

  • Option 2

    EcoFlow DELTA 2 Max

    2,048 Wh · 2,400W · 50 lb

    Double the tank of the DELTA 2 for people who want to sleep through the night without checking a screen.

    Link not set

  • Option 3

    Bluetti AC200L

    2,048 Wh · 2,400W · 61.9 lb

    A lot of battery for the money, with the port selection of a small workshop.

    Link not set

These are estimates built from typical appliance figures, not measurements of your exact fridge. Check the label on the back of your appliance for its real draw before you spend money.

Sizing & Calculators