Last updated: April 22, 2026
A portable power station has two numbers that matter. Watt-hours (Wh) tells you how much total energy the unit stores — think of it as the size of the fuel tank. Watts (W) tells you how much power it can deliver at one time — think of it as the engine. You need both numbers to answer the question, and neither one alone is enough. A 2000Wh unit with a 1000W output can’t run a 1500W appliance even though its tank is large. A 1000W unit with 500Wh of capacity can technically run a 1000W device but only for about 25 minutes.
Find your use case in the left column. The right column tells you the minimum capacity tier to look for — not the maximum. Going larger always works; going smaller means running out of power before the job is done.
| What You Need to Power | Examples | Minimum Size |
|---|---|---|
| Phones, tablets, small devices only | Charging phones, earbuds, cameras, LED lights | 300–500Wh |
| CPAP machine overnight — no humidifier | 8 hours at 30–60W = 240–480Wh needed | 300–500Wh |
| Laptop + devices for a day | Laptop (varies by model), phone, tablet, small fan | 500–700Wh |
| CPAP with heated humidifier overnight | 8 hours at 60–120W = 480–960Wh needed | 700–1000Wh |
| Mini fridge or electric cooler running all day | Compressor cooler averaging 40–60W continuously | 700–1000Wh |
| Home office through a full outage | Laptop, monitors, router, phone charging — 8 hours | 1000–1500Wh |
| Full-size refrigerator overnight | Average 1–2 kWh/day (DOE); compressor surges to 3× running watts | 1500–2000Wh |
| Fridge + lights + devices through a multi-day outage | Essential home backup, storm prep | 2000Wh+ |
| Sump pump, power tools, microwave | High-surge motor loads — check the unit’s surge watt rating, not just capacity | 2000Wh+ |
The table above gives you a starting point by use case. The rest of this guide explains why those numbers are what they are, what you can realistically expect at each tier, and which appliances tend to fool people regardless of what size they buy.
The One Formula You Need
Before anything else, here’s how to estimate runtime for any device on any power station:
Runtime (hours) = (Battery Wh × 0.85) ÷ device watts
The 0.85 accounts for the energy lost when the inverter converts the battery’s DC power to the AC power your appliances use. That conversion isn’t free — quality inverters lose roughly 10–15% as heat. If you’re running a device through a DC port or USB-C port directly, use 0.92 instead — those ports skip the inverter and lose less.
One example: a 1000Wh unit running a 60W device through AC. (1000 × 0.85) ÷ 60 = about 14 hours.
The same unit running a refrigerator that averages 150W when the compressor is running: (1000 × 0.85) ÷ 150 = about 5.6 hours.
That second number is why fridge runtimes on the box look different from what people actually get. The unit is working correctly — the math just doesn’t produce the number people were hoping for.
One important qualifier on device wattage: the number on the front of an appliance is often not its input draw. A microwave labeled “700W” refers to its cooking output power, not the electricity it pulls from the wall — actual input is typically 1100–1200W. For the most accurate number, check the sticker on the back of the appliance or the label on its power adapter, not the marketing spec on the front.
What a 300–500Wh Unit Can Handle
This is the device-charging tier. A 300–500Wh unit is well suited for situations where you need to keep small electronics running and have no expectation of powering anything with a motor or heating element.
What it handles reliably: smartphones charge around 10–15Wh each depending on battery size, so a 300Wh unit can fully charge most phones 20+ times. Tablets charge at 20–40Wh. Laptops vary significantly by model — check your power adapter’s wattage rating, not the laptop’s marketing spec — but many charge at 45–65W, giving you several full charges from a 500Wh unit. LED lights draw very little, typically 5–15W, and can run for many hours. Portable Bluetooth speakers, drones, camera batteries, and similar small devices are all well within this tier.
CPAP machines without the heated humidifier fit comfortably here. Most CPAP machines draw 30–60W during normal operation according to manufacturer specifications. Eight hours at 40W works out to 320Wh — within a 500Wh unit’s range with capacity to spare. If your machine uses a heated humidifier, that draw climbs to 60–120W and changes the calculation significantly — see the 700–1000Wh section below.
What this tier cannot do: anything with a motor or compressor (refrigerators, air conditioners, most power tools), anything with a heating element (coffee makers, electric kettles, toasters, space heaters), or sustained high-draw appliances. These aren’t failures of a 300–500Wh unit — they’re simply outside what this tier was designed for.
Who this is for: weekend campers keeping phones and cameras charged, travelers who need their CPAP backed up for one night without humidification, people who want a simple device-charging backup for power outages.
What a 500–1000Wh Unit Can Handle
This is the most commonly purchased tier, and also the tier where expectations most often diverge from reality. A 1000Wh unit sounds substantial — and it is, for the right use cases — but it has real limits that are worth understanding before you buy.
Laptops and work setups: A laptop charging at 65W through USB-C runs for roughly 12 hours on a 1000Wh unit using the formula above (1000 × 0.92 ÷ 65). Add a monitor, a router, and phone charging and your draw climbs — but a typical home office setup running modestly can get through a full workday on 1000Wh if you’re not running the office through the AC outlet exclusively.
CPAP with humidifier: At 60–120W, a CPAP with heated humidification running for 8 hours needs 480–960Wh. A 1000Wh unit covers this, but on the higher end of the humidifier range you’re close to the limit. A 700Wh unit is marginal. If CPAP reliability is the primary reason you’re buying, size up rather than cutting it close — sleep apnea therapy isn’t something you want to power down midway through the night.
Mini fridges and compressor coolers: A quality compressor-style camping cooler draws 40–60W on average. A 1000Wh unit handles this well — (1000 × 0.85) ÷ 50 = 17 hours of runtime on a 50W average draw. These coolers cycle on and off like a refrigerator, so the average draw is lower than the peak. For a weekend camping trip, a 1000Wh unit runs a compressor cooler reliably.
Full-size refrigerators: This is where the 1000Wh tier gets complicated and where people are most frequently disappointed. A standard full-size refrigerator uses between 1 and 2 kWh per day according to DOE Energy Saver guidance, which works out to an average draw of roughly 40–85W when accounting for the compressor cycling on and off about one-third of the time. On that average, a 1000Wh unit looks like it should run a fridge for 10+ hours. The problem is the surge.
When a refrigerator compressor starts, it briefly pulls 2–3 times its running wattage. A fridge running at 150W during compressor operation may surge to 300–450W at startup. If your power station’s continuous output rating or surge rating can’t cover that spike, the unit trips its protection circuit and shuts off — even if there’s plenty of battery capacity remaining. Whether a 1000Wh unit successfully runs a full-size fridge depends entirely on that specific unit’s surge watt rating and your specific refrigerator’s startup draw. There’s no universal answer. Before buying, check the surge watt specification on the power station and the locked rotor amperage on your refrigerator’s compressor label.
Who this tier is for: multi-night campers with a compressor cooler, home office backup for a workday, CPAP users including humidifier, people who want a useful outage backup for devices and lighting without expecting to run the kitchen.
What a 1500–2000Wh Unit Can Handle
At this tier, you’re in genuine home backup territory. A 2000Wh unit with a continuous output rating of 2000W or higher handles most of what a household needs during an outage, with meaningful exceptions noted below.
Full-size refrigerators: With adequate surge capacity, a 2000Wh unit runs most full-size refrigerators reliably. The Department of Energy’s data puts average refrigerator consumption at 1–2 kWh per day — a 2000Wh unit comfortably covers 24 hours on the lower end of that range. In practice, overnight backup for a fridge typically uses 800–1200Wh depending on how often the door is opened, ambient temperature, and how full the fridge is. A 1500–2000Wh unit handles this with capacity left over for lights and device charging.
Sump pumps: Sump pumps are motor loads with significant startup surge — typically 800–1200W to start, settling to 400–800W running. Whether a specific power station handles a specific sump pump depends on both the surge rating of the unit and the locked rotor amperage of the pump. A 2000Wh unit with a 4000W+ surge rating handles most residential sump pumps. A unit with a lower surge rating may not, regardless of its capacity. Check both specs before relying on this for flood protection.
Microwave: A microwave’s input draw is typically 1000–1500W, considerably higher than its labeled cooking power. On a 2000Wh unit with adequate output, a microwave works — but it drains the battery quickly. At 1200W input, (2000 × 0.85) ÷ 1200 = about 1.4 hours of continuous use. In practice, nobody runs a microwave continuously — a few 2–5 minute heating sessions use a fraction of that. For periodic reheating during an outage, a 2000Wh unit handles this fine.
Power tools: Circular saws, drills, and similar tools have high startup surge and variable running draw. Intermittent use during an outage — cutting wood for repairs, for example — is generally within what a 2000Wh unit with strong surge capacity handles. Sustained heavy tool use over hours is not what this tier is designed for.
Who this tier is for: homeowners in storm or hurricane-prone areas who need genuine multi-day essential backup, anyone who needs fridge plus lights plus device charging through an extended outage, households with a sump pump in a flood-risk area.
What No Portable Power Station Handles Well
This is the section most buying guides skip because naming limitations doesn’t sell units. These are appliances where the physics don’t work in your favor regardless of size.
Space heaters: A standard space heater draws 1500W continuously. At that rate, (2000 × 0.85) ÷ 1500 = about 1.1 hours from a 2000Wh unit. A 1000Wh unit lasts about 35 minutes. Space heaters are genuinely impractical for portable power station use in any cold weather scenario where you’d actually need one. Blankets, layered clothing, and a smaller unit dedicated to essential devices are a better approach to cold-weather outage planning.
Central air conditioning and heat pumps: These are 240V systems drawing 3000–7000W or more. Portable power stations operate on 120V and top out well below what central HVAC requires. No portable power station runs central air or a whole-home heat pump. Portable window AC units (5000 BTU) draw 400–600W and some larger units can run them briefly, but runtime is short and the use case is marginal at best.
Electric water heaters, dryers, and ranges: These are 240V high-draw appliances. A standard electric water heater draws 4000–5500W. An electric dryer draws 5000–7500W. An electric range draws 3000–12000W depending on what’s running. None of these are compatible with portable power stations. If your home depends on electric appliances for these functions, a whole-home battery system — not a portable power station — is the appropriate backup solution.
EV charging: A Level 1 charger (standard 120V outlet) adds about 3–5 miles of range per hour at 1000–1500W. From a 1000Wh unit, you’d add roughly 2–3 miles of range total before draining the battery. This isn’t a useful application. Level 2 charging (240V) is incompatible entirely.
One note on electric kettles and coffee makers: these draw 800–1500W but only for 3–8 minutes per use, consuming 40–100Wh per cycle. A single pot of coffee or one kettle boil is within what a 500Wh unit handles without much impact. These appliances are fine for occasional use — they’re not fine for sustained continuous use.
How to Calculate Your Own Situation
The sizing table above gives general guidance. For your specific situation, work through this:
Step 1 — List what you actually need to power. Not everything you’d like to power in a perfect world — what genuinely needs to stay on. Fridge? CPAP? Modem and router? Lights? Be specific.
Step 2 — Find the wattage of each device. Check the nameplate sticker on the appliance (usually on the back or bottom), not the marketing spec. For the most accurate reading, a plug-in power meter measures actual draw in real time — useful if you want to know what your specific refrigerator actually pulls rather than relying on averages.
Step 3 — Estimate hours of use. How long does each device need to run? A fridge runs 24 hours but the compressor is only active about one-third of that time. A CPAP runs 7–8 hours per night. Lights might run 4–6 hours. Be realistic.
Step 4 — Run the formula for each device. (Device watts × hours of use) ÷ 0.85 = Wh needed from the battery for that device.
Add the totals together. That’s your minimum Wh requirement. Then add 20–25% as a buffer for cold temperatures, battery age, and the fact that estimated wattages are just that — estimates.
Step 5 — Check the output rating, not just the capacity. For any motor appliance — fridge, sump pump, power tool — verify that the unit’s surge watt rating exceeds the appliance’s startup draw. Capacity without adequate output rating is a mismatch that no amount of Wh solves.
Frequently Asked Questions
What’s the difference between watts and watt-hours on a power station? Watts (W) measures how much power the unit delivers at one moment — it determines what you can plug in. Watt-hours (Wh) measures how much total energy the unit stores — it determines how long things run. A unit with 2000W output and 500Wh capacity can run a 2000W appliance, but only for about 12 minutes. A unit with 500W output and 2000Wh capacity runs a 100W device for 17 hours but can’t power a 1500W appliance at all. You need both numbers.
Can a 1000Wh power station run a refrigerator? It depends on your refrigerator’s startup surge and the unit’s surge watt rating. The average power draw of a full-size refrigerator is 1–2 kWh per day (DOE Energy Saver), which looks manageable. The problem is the compressor’s startup surge, which can briefly hit 2–3 times running wattage. If the power station’s surge rating can’t cover that spike, it shuts off. Check both the power station’s surge specification and your refrigerator’s locked rotor amperage before assuming it will work.
What size power station do I need for camping? For most camping use — charging phones, a laptop, running lights and a small fan — a 500Wh unit covers a weekend comfortably. If you’re bringing a CPAP without humidifier, 500Wh is typically sufficient. If you want to run a compressor cooler all day alongside devices, 1000Wh is the more reliable choice. For extended trips with heavy use, plan around your specific devices using the formula above rather than a general tier recommendation.
Can any portable power station run an air conditioner? Portable window units (5000 BTU) draw 400–600W running, with higher startup surge. Some 2000Wh units with strong surge ratings can run a small window AC unit, but runtime is short — roughly 2–3 hours — and the unit will be working at or near capacity. Central AC systems are 240V and incompatible with portable power stations entirely.
What size do I need for a CPAP machine? Without a heated humidifier, most CPAP machines draw 30–60W. Eight hours of use requires 240–480Wh. A 500Wh unit covers this with room to spare and is the standard recommendation for CPAP camping backup without humidification. With a heated humidifier, draw climbs to 60–120W, putting eight hours of use at 480–960Wh. For humidified CPAP use, a 1000Wh unit is the reliable choice. Check your specific machine’s specification label for its rated wattage — these numbers vary meaningfully between models.
Does a power station need to be a pure sine wave inverter for sensitive electronics? Most modern portable power stations use pure sine wave inverters, which produce the same type of power as a standard wall outlet and are safe for all electronics including medical equipment, laptops, and audio gear. Modified sine wave inverters — less common in current consumer units but still found in some budget models — can cause problems with sensitive electronics, motor-driven appliances, and some medical devices including CPAP machines. Check the specifications before purchasing if this matters for your use case.
For help diagnosing why your existing power station isn’t lasting as long as expected, see our guide.
For the full portable power station troubleshooting index.
Sources: U.S. Department of Energy — Estimating Appliance and Home Electronic Energy Use (energy.gov/energysaver); DOE Energy Guide label methodology for refrigerator average consumption; CPAP wattage ranges from manufacturer specifications (ResMed, Philips Respironics) and CPAPtalk.com measured data. Inverter efficiency standard (85% AC, 92% DC) consistent with published portable power station manufacturer documentation. All runtime figures are estimates — actual results vary by specific appliance model, ambient temperature, battery age, and usage pattern. Check your specific appliance’s nameplate for its actual wattage before making purchasing decisions.