What Size Power Station Do I Need?

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To keep a household’s essentials running for a full day without recharging, most homes need a power station of about 2,000–3,300Wh with at least 1,800W of continuous output. A day of fridge, internet, phone charging and lighting uses about 1,500–2,500Wh; the capacity figure adds the 30% headroom explained below for inverter loss, cold and battery age. The fridge and small loads alone need about 1,000W continuous and a 2,000W surge rating, and 1,800W leaves room for a microwave or kettle. Add a gas furnace blower in winter and a day’s load comes to about 3,000–4,000Wh or more, or less with a variable-speed (ECM) blower. But the right number depends entirely on what you plan to run and for how long, and the arithmetic that gets you there takes about five minutes.

Quick answers by use case

If you want the short version, find your situation in the table below, then read on to check the reasoning. Every figure here already assumes you will lose 10–15% of the advertised capacity to inverter losses, which is covered in detail further down.

The mistake almost everyone makes

Nearly everyone shops by price. They pick the largest unit within budget, and then discover it either does not start what they needed or dies hours too early. Size is not a budget decision. It is an arithmetic one.

The reason the mistake is so common is that power stations are sold on one number — capacity in watt-hours — and that number answers only half the question. Capacity tells you how long. It tells you nothing about whether the thing turns on at all. Those are two separate specifications, governed by two separate parts of the machine, and a unit can be generous on one and hopeless on the other.

Work through the three steps below and you will end up with two numbers instead of one: a watt-hour figure and a watt figure. Shop against both.

Step 1: list what must stay on

Not what you would like powered — what genuinely must be. This distinction is worth being strict about, because it is usually the difference between a $600 purchase and a $2,400 one.

For most households in an outage the real list is short:

• The fridge and freezer. Not for comfort — for the several hundred dollars of food inside them.
• Internet and phones. Router, modem and chargers. Tiny loads with outsized value.
• Some lighting. A few LED lamps, not the whole house.
• Medical equipment. A CPAP, a nebulizer, an oxygen concentrator. Non-negotiable if it applies to you.
• Heat, in winter. If you have a gas furnace this means the blower only, which is a much smaller job than people assume.

What is usually not on the list: electric ovens, clothes dryers, central air conditioning, electric water heaters and anything else that makes heat with electricity. These are enormous loads, and a portable battery is the wrong tool for them. If you need those running you are looking at a whole-home battery system or a generator, not a portable unit.

Step 2: add up the watt-hours

A watt-hour is one watt drawn for one hour. Multiply each item by its average draw and the number of hours you need it, then add the results together. The word average is doing a lot of work in that sentence and is the most misunderstood part of sizing — see the fridge note below.

A typical “keep the essentials alive” day lands around 1,500–2,500Wh. That is the load, not the battery to buy. With the 30% headroom covered below, it points to about 2,000–3,300Wh of rated capacity for a full day, or a 2,000Wh unit plus a way to recharge it.

Notice how cheap the small things are and how expensive the heat-producing things are. A router costs you a few hundred watt-hours across an entire day. A coffee maker costs a hundred watt-hours in five minutes. Anything with a heating element — kettle, toaster, hair dryer, space heater — will empty a battery faster than everything else on your list combined.

The fridge deserves its own paragraph

A fridge does not draw its rated wattage continuously. The compressor cycles on and off, typically running about a third of the time in a cool room, so a fridge with a 150W compressor averages something closer to 50W across the day. People who size using the label figure end up buying two or three times more battery than they need. This is common enough that we wrote a separate guide on refrigerator wattage, and it is worth reading before you commit to a number.

Working backwards: what a battery you already have will run

Steps 1 and 2 turn a list of loads into a capacity. The same arithmetic runs in reverse when you already own a unit, or are choosing between a 1,000Wh and a 2,000Wh one. Usable energy is the rated capacity less inverter loss. This table takes 15% off, the conservative end of the 10–15% inverter loss covered below, so a 1,000Wh unit delivers 850Wh and a 2,000Wh unit 1,700Wh. Runtime is usable watt-hours divided by the average draw.

Three things to know when reading it. The fridge rows use a 60W average rather than the compressor’s rated draw, for the reason given above. The furnace row counts running time only: a blower that runs one hour in three turns 3.8 running hours into about 11 on the clock. And the heater row only works on a unit whose output reaches 1,500W, and even a 2,000Wh battery buys about an hour of heat, which is the clearest case for a generator rather than a battery — see power station vs generator.

These are new-battery, room-temperature figures. Cold and age take more off, which is why the 30% headroom below still applies. For the draw of a specific appliance, use the appliance wattage chart; for CPAP machines, how many watts a CPAP uses separates the blower from the humidifier.

Step 3: check the inverter, not just the battery

Capacity decides how long. Output decides whether it starts at all. A 2,000Wh battery paired with a 1,000W inverter cannot run a 1,500W kettle for one second. It will simply refuse, or trip, and no amount of stored energy changes that.

Two output numbers matter:

• Continuous output — what the inverter sustains indefinitely, in watts. Add up everything you might have running at the same time and stay under this.
• Surge or peak output — a brief allowance, usually a second or two, for motors starting. Compressors, pumps and power tools draw three to seven times their running current at the instant they start; a fridge compressor sits at the top of that range.

That surge is why a fridge averaging 60W still needs an inverter rated far higher. The compressor might pull 1,000–1,500W for a fraction of a second every time it kicks in.

Most households want at least 1,800W of continuous output. 2,400W is comfortable. Below 1,000W you are limited to electronics and lighting, which is fine if that is genuinely all you need and a waste of money if it is not.

Do you need 240V?

Watts are not the only output limit. A power station with only standard 120V outlets cannot run an appliance built for 240V, however large its battery. Well pumps are the load to check. In Franklin Electric’s 4-inch submersible motor line, single-phase 60Hz motors are made in 115V only at 1/3 and 1/2 hp, and those sizes also come in 230V; every motor from 3/4 hp up is 230V. So even the 1/2 hp pump in the table above may be a 240V load. Read the voltage on your pump’s nameplate or in its manual before you shop.

Units that do offer 240V handle it differently. EcoFlow’s FAQ for the DELTA Pro 3Check price on Amazon↗ (4,096Wh) says it does not output 120V and 240V at the same time but can supply split-phase power on its own: its 240V button turns on an L14-30 split-phase socket and a 240V outlet and switches the 120V outlets off. EcoFlow says that L14-30 socket, connected to an inlet box, powers 120V and 240V home appliances. BLUETTI says the Apex 300 (2,764.8Wh, 3,840W) powers 120V and 240V devices at the same time. In both cases the pump’s start still has to fit inside the surge rating, which the table above puts at 2,000–3,000W for a 1/2 hp well pump.

How output, weight and cost change between 1,000Wh and 2,000Wh

Capacity and output are separate specifications, and among the power stations we track they are tied far more loosely at the smaller size. The table covers every one whose maker publishes a capacity in that band. Some are variants or bundles of the same unit, so read the counts as a rough weighting rather than a tally of distinct models.

Around 1,000Wh, the output figure is what separates units. Two entries with almost the same battery:

• Jackery Explorer 1000 Pro Portable Power Station — 1,002 Wh, 1,000W continuous.
• ALLPOWERS P1800 Portable Power Station 1024Wh | 1800W — 1,024 Wh, 1,800W continuous, an inverter rated 80% higher.

Only the second meets the 1,800W this guide treats as the household minimum. Around 2,000Wh, every entry that publishes an output clears 1,800W, so the inverter is rarely what limits you. Weight and cost are: the median unit nearly doubles in weight, while the median price per watt-hour falls, consistent with the price index, which finds the cheapest watt-hours in the 1,200–2,600Wh class.

The cheapest watt-hours are not always the best covered. These are the three lowest prices per watt-hour among the 2,000Wh power stations we track, with the warranty each maker states:

• PECRON E2400LFP Portable Power Station 2400W 2048Wh — 1 year.
• ALLPOWERS R2500 V2 Portable Power Station — 5 years.
• OUPES Mega 2 Home Backup & Portable Power Station — 1 year.

Put warranty next to price when you compare.

Why you never get the number on the box

Advertised capacity is the raw cell rating. What reaches your appliance is meaningfully less, for three reasons that stack.

Inverter losses

Converting stored DC into household AC costs roughly 10–15% of the energy. A 1,000Wh unit realistically delivers 850–900Wh to something plugged into its AC socket. Charging a laptop or phone from the DC or USB-C ports skips part of that conversion and is noticeably more efficient, which is worth knowing when you are rationing.

Cold weather

Lithium cells lose capacity as temperature drops. At freezing you might see 70–80% of the rated figure, and most batteries refuse to charge below 0°C entirely unless they have a heating system built in. This matters enormously if the battery lives in a garage, a van or an unheated basement, which is exactly where people tend to store them.

Age

Every battery loses capacity over its life. A LiFePO4 pack rated for 3,000 cycles to 80% means that after 3,000 full charges it holds 80% of what it did when new. That is a good result — older lithium-ion chemistries reach the same point in 500 to 1,000 cycles. Our chemistry comparison covers why the difference is so large and why it should shape your purchase.

A worked example, start to finish

Here is one household taken through all three steps, using the figures from the tables above.

Step 1. The must-stay-on list: a full-size fridge, the router and modem, four LED lamps, two phones and a CPAP used without its heated humidifier.

Step 2. The watt-hours for one day:

Add the 30% headroom and the target is about 3,100Wh of rated capacity. A 2,000Wh unit, which delivers about 1,700Wh after inverter loss, runs this list for about 17 hours, not a full day.

Step 3. Everything running at once comes to under 400W: the fridge compressor at 100–250W plus about 115W for the rest. The limit is the fridge’s start, 1,000–1,500W for a moment, so the inverter needs at least 1,000W continuous and about 2,000W of surge, or 1,800W continuous if a microwave or kettle will share it.

The answer for this home is about 3,100Wh with those output ratings, or a 2,000Wh unit with solar or a generator to top it up each day. Leaving the CPAP’s heated humidifier on would add roughly another 320Wh a night.

Sizing by scenario

Weekend camping

Phones, a camera battery, a couple of lights, maybe a small fan. Realistically 200–400Wh across a weekend. A 250–500Wh unit is right, and the deciding factor is usually weight rather than capacity, because you will be carrying it. Anything above about 1,000Wh stops being genuinely portable for one person.

Car camping and overlanding

Add a 12V fridge, which is the big change: 300–600Wh per day on its own. A 1,000Wh unit gets you two days, and paired with 100–200W of solar you can stay out indefinitely in decent weather. Check the solar input rating before buying panels — some units accept far less than people assume, and the panel that came bundled is often not the one you want.

Van life and full-time off-grid

Here the arithmetic changes character, because you are not surviving an event, you are living a life. Budget 1,500–3,000Wh per day with a fridge, laptop work and Starlink. You want 2,000Wh+ of storage and 400W+ of solar, and you need to think about charge rates and recharge time rather than capacity alone. Our solar sizing guide covers the panel side properly, and the off-grid RV section covers the vehicle-specific parts.

A short power cut

Four to eight hours, a few times a year. You need the fridge, the router and some light: roughly 400–800Wh. A 1,000Wh unit is comfortable and costs a fraction of a home system. The fridge is the item on a clock. CDC food-safety guidance says that with the doors kept closed, food stays safe for up to 4 hours in a refrigerator, 48 hours in a full freezer and 24 hours in a half-full one. After 4 hours without power or a cold source such as ice, CDC says to throw out perishable food in the fridge (meat, fish, cut fruit and vegetables, eggs, milk and leftovers), so in a six- or eight-hour cut the fridge is the load worth keeping powered. CDC also advises keeping an appliance thermometer in the fridge, which should read 40°F or below.

A multi-day outage

This is the scenario that justifies real money. Three days of essentials at 1,500–2,500Wh per day is 4,500–7,500Wh of load, or about 5,900–9,800Wh of rated capacity once the 30% headroom is added. A single large unit such as Jackery’s 5,040Wh Explorer 5000 Plus still falls short of that on its own. Your options are an expandable system with extra battery modules such as the Bluetti Apex 300 or EcoFlow Delta Pro 3, a unit plus solar to recharge during daylight, or a permanently installed home battery. Solar is the part people skip and then regret — without a way to recharge, even a very large battery is a one-shot device.

CPAP and medical equipment

Size generously and buy a second charging route. A CPAP without the heated humidifier draws about 30W, or about 40W from a power station’s AC outlet once the inverter’s idle draw is counted, so a 1,000Wh unit covers two or three nights. Turning the humidifier off in an outage roughly doubles your runtime. If the equipment is genuinely life-sustaining, treat a battery as one layer rather than the whole plan, and ask your utility about its medical baseline or medical-needs registration. These programs typically give advance notice of planned shutoffs and some protection from disconnection, but they do not guarantee faster restoration, so plan your backup for a full-length outage.

When to buy expandable instead

If your answer sits near a boundary, or you suspect your needs will grow, buy into a system that accepts extra battery modules rather than a sealed unit at the top of your budget.

Expandable systems cost more per watt-hour at the entry point and less overall if you ever expand. They also let you spread the cost across years, which for a purchase this size is often the deciding practical factor. The catch is that you are committing to one manufacturer’s ecosystem — expansion batteries are not interchangeable between brands, and a discontinued line can leave you stranded. Buy expandable from a brand with a long product history and a large installed base.

You can see which units accept expansion batteries using the comparison tool.

Five sizing mistakes worth avoiding

1. Sizing on peak wattage instead of average. The fridge problem. It inflates your requirement by a factor of two or three.
2. Ignoring the inverter rating. Buying capacity you cannot use, because nothing heavy will start.
3. Forgetting the recharge. A battery with no solar and no generator is a single-use device in a real outage.
4. Including heat-producing appliances. Kettles, heaters and hair dryers belong on a generator or on nothing.
5. Sizing exactly. No headroom for cold, for age, or for the load you forgot.

Frequently asked questions