How Many Watt-Hours Do You Need?

A power station can look impressively large on a shelf and still run out before breakfast—or be far more battery than your weekend campsite needs. The deciding number is watt-hours, abbreviated Wh. It tells you how much energy the battery stores. A phone, router and LED lamp barely sip from that reserve. A refrigerator, coffee maker or heated CPAP humidifier can drain it quickly.

This guide gives you a repeatable sizing method. List each device, estimate its watts and hours of use, multiply them, then account for the roughly 85% of stated battery capacity that is practically available through AC output. Add a 20–30% cushion for startup surges, changing conditions and imperfect estimates. You will also find realistic outage, camping, van-life and job-site examples, plus a runtime table and power-station illustrations.

Our recommendations use manufacturer-listed capacity and output specifications, the stated value for each size class, and the volume of Amazon customer ratings as a useful popularity signal. For broader buying context, compare this method with our complete power-station buying guide, then check the current price on Amazon.

Start with watts, hours and your real routine

Write down every device you expect to power and separate essential loads from nice-to-have loads. During a blackout, that might mean a refrigerator, Wi-Fi router, phone chargers, a lamp and a CPAP machine. At a campsite, it may be a laptop, camera batteries, lights and a small cooler. Do not size around a vague phrase such as “a few appliances.” Name the devices and estimate how long each will run.

For each item, use this basic calculation: watts × hours of use = watt-hours. A 10 W router running for 12 hours uses about 120 Wh. A 60 W laptop used for 5 hours uses about 300 Wh. A 5 W LED lamp used for 6 hours uses 30 Wh. Add those figures together rather than focusing only on the biggest device.

Daily habits matter. A refrigerator may not draw its listed running wattage continuously because its compressor cycles. A laptop charger may draw less than its maximum rating once the battery is nearly full. When you do not know the exact consumption, use the device’s rated wattage as a conservative estimate and build in the margin described below. For CPAP sizing, include the machine’s stated draw and separately account for heated humidity or a heated hose if you plan to use them.

The 85% usable-capacity rule

The capacity printed on a power station is the battery’s nominal storage, not the exact energy delivered to an AC appliance. Conversion electronics consume some energy, so a practical planning figure is capacity × 0.85. A 1,000 Wh station therefore gives you about 850 Wh for an AC load under this rule. This is a planning estimate, not a promise for every device or operating mode.

USB and DC loads can differ from AC loads because they may avoid some conversion losses. For consistent comparisons, however, using 85% keeps your calculations simple and prevents optimistic estimates. It is especially useful when comparing a laptop, router or lamp connected through different output types.

Next, add a 20–30% reserve to your calculated demand. If your devices total 600 Wh, multiplying by 1.2 gives a sensible minimum target of 720 Wh; multiplying by 1.3 gives 780 Wh for more breathing room. This reserve covers changing device use, cold weather, startup demands and the temptation to plug in one more item. For sensitive equipment, overnight medical use or an uncertain refrigerator load, use the larger reserve. For a tightly controlled phone-and-light kit, the smaller reserve may be adequate.

A worked sizing example for a blackout

Imagine a 12-hour overnight outage. Your router uses 10 W for 12 hours, a lamp uses 8 W for 6 hours, two phones together average 10 W for 3 hours of charging, and a laptop averages 60 W for 4 hours. The energy estimate is 120 Wh + 48 Wh + 30 Wh + 240 Wh, or 438 Wh.

Apply the 20% reserve: 438 Wh × 1.2 = about 526 Wh of useful energy required. Because the station’s stated capacity is not all available at the outlet, divide by 0.85. The resulting target is about 619 Wh of nominal battery capacity. In practice, the next sensible class is around 700 Wh or 1,000 Wh, depending on how long the outage may last and whether you want refrigerator backup.

Now add a refrigerator and the answer changes dramatically. Even if its average energy use is modest, its compressor can demand a high startup surge. You need enough battery for the expected hours and enough AC output for the refrigerator’s running and surge requirements. A 1,000 Wh-class unit such as the Anker SOLIX C1000 provides 1,056 Wh, while the BLUETTI AC180 provides 1,152 Wh and 1,800 W rated output. Verify your appliance’s wattage and startup requirements before ordering.

Runtime table: quick estimates at common loads

The table below uses the same planning equation: runtime = battery Wh × 0.85 ÷ watts. These are approximate AC-load runtimes before adding your own reserve. A device with a compressor, heating element or variable-speed motor may behave differently because its draw changes over time. The numbers are most useful for comparing capacity classes and spotting an undersized choice.

For a deeper appliance-by-appliance look, see what a 1,000 Wh power station can run. Remember that these figures describe one steady load; several devices add together.

Compact tier: phones, lights, laptops and short trips

A roughly 250–300 Wh station is a sensible starting point for personal electronics, short camping trips and a small emergency kit. It can cover phones, camera batteries, LED lighting, a router and modest laptop use, provided you are not also running a heater, coffee maker or refrigerator. The output rating matters just as much as capacity: a battery may have enough Wh for a device but still lack the watts to start or operate it.

The Jackery Explorer 300 stores 292 Wh and has a 4.6 Amazon rating from 11,300 ratings. Its value for its size class is Fair. It is a straightforward illustration of the compact tier and qualifies for the under-$300 category; check the current price on Amazon.

The Anker SOLIX 521 stores 256 Wh and is rated for 300 W AC output. Its title also identifies a 600 W peak, LFP chemistry and optional solar-panel compatibility. It has a 4.4 rating from 3,100 ratings and Premium price value for its size class. The Anker SOLIX C300 offers 288 Wh and 300 W output, with 600 W surge, 140 W two-way USB-C and seven charging ports. It has a 4.6 rating from 1,900 ratings and Premium price value. These compact choices suit low-wattage loads, not electric cooking or space heating.

The 1kWh tier: the versatile middle ground

Around 1,000 Wh is where a power station becomes useful for much more than device charging. After the 85% planning adjustment, this class offers roughly 850 Wh for AC loads. That can cover many hours of networking, lights and laptop use, or support a refrigerator while you manage the rest of your household demand. It is also a practical size for car camping, van builds and job sites where tools are intermittent rather than continuously drawing power.

The Anker SOLIX C1000 has 1,056 Wh, a 4.7 rating from 2,100 ratings and Good value for its size class. Its listed features include 2,400 W SurgePad output, nine ports, 3,000 battery cycles and up to 600 W solar input. The Jackery Explorer 1000 v2 has 1,024 Wh, a 4.7 rating from 3,700 ratings and Premium price value. It lists 1,500 W AC output, 3,000 W surge, six ports, 100 W USB-C and LFP chemistry.

Either example has the capacity to handle a broad essential-load list, but do not confuse battery size with appliance compatibility. Check the starting wattage of refrigerators, pumps and power tools. For solar planning, see our solar charging guide.

The larger 1.1kWh tier: more output and outage headroom

When your list includes a refrigerator, CPAP equipment, networking gear and several household essentials, a little extra capacity and output can make the difference between careful rationing and a comfortable night. A 1,100 Wh-class station gives you approximately 935 Wh under the 85% rule. That is not an unlimited home battery, but it provides useful headroom for changing loads and compressor starts.

The BLUETTI AC180 is the strongest capacity-and-output illustration here: 1,152 Wh, 1,800 W rated AC output and 2,700 W peak output. It has a 4.5 Amazon rating from 1,900 ratings and Excellent value for its size class. Its listed features include nine outlets, an emergency UPS response of 20 ms, LFP chemistry and up to 500 W solar input.

For a 100 W steady load, the calculation is 1,152 × 0.85 ÷ 100, or about 9.8 hours. At 300 W, it is about 3.3 hours. Those figures are useful for planning, but an electric kettle, hot plate, hair dryer or space heater can consume energy far faster than electronics. If medical equipment is involved, prioritize the manufacturer’s power information and consider a larger reserve. Our home-backup guide covers the broader trade-offs.

Choose the right tier for your situation

Under 300 Wh: Choose this tier for phones, tablets, lights, camera batteries, a router and short laptop sessions. It is easy to justify for camping or a desk-side emergency kit, but it is usually a poor match for refrigerators, heating appliances and long CPAP nights with heated humidity.

About 500–800 Wh: This is the flexible personal-backup range. It suits a longer electronics outage, several campsite days with disciplined use, or a CPAP setup when the machine’s actual draw is modest and humidity is controlled. Use your calculation rather than assuming a standard runtime.

About 1,000–1,200 Wh: This is the best all-purpose target for many households. It can support a refrigerator, router, lights, phones and a laptop for a defined outage period, subject to appliance draw and output limits. The under-$1,000 guide is useful when comparing this class.

Above 2,000 Wh: Consider this for extended outages, larger refrigerators, multiple high-draw essentials, van living or workshop use. You pay in portability and planning complexity, but gain endurance. For true whole-home expectations, compare power stations and gas generators rather than assuming any portable battery can replace a generator.

Common sizing mistakes to avoid

The first mistake is buying by output wattage alone. A 1,800 W inverter tells you what the station may run at once; it does not tell you how long. A second is buying by watt-hours alone. A large battery with an insufficient inverter may not start your refrigerator, pump or tool. Check both continuous and surge output.

Another mistake is forgetting the reserve. If your device list totals 700 Wh, a 700 Wh battery is not a comfortable target once conversion losses are included. Apply the 0.85 usable-capacity rule, then add 20–30% to the demand. Also separate starting loads from running loads. Motors and compressors can briefly demand much more than their normal draw.

Do not automatically count every appliance in the house. During a blackout, choose essentials and stagger charging. A coffee maker may use more energy in minutes than a router uses for hours. Heated CPAP humidity and hoses can materially change overnight consumption. Finally, avoid treating solar as an instant refill: panel conditions, sunlight and input limits affect recharge time. For storm preparation, pair sizing with our hurricane and blackout checklist.

Final recommendation: buy for your essential load, not a fantasy load

The most reliable sizing habit is simple: make a device list, multiply watts by hours, total the result, multiply your target by 1.2 or 1.3, then divide by 0.85 to translate that demand into nominal battery capacity. Round up to the next sensible class. If an appliance has a motor or heating element, check its startup and continuous wattage separately.

For a small electronics kit, the 256–292 Wh examples are appropriate starting points. For a broad mix of electronics and selected appliances, the 1,024–1,152 Wh examples offer a more comfortable reserve. The Anker SOLIX C1000 is the balanced 1kWh illustration, while the BLUETTI AC180 adds output and capacity. The Jackery Explorer 1000 v2 is another premium 1kWh option. Compare value labels, output, charging options and customer ratings—not capacity in isolation.

For CPAP, outage and medical-device planning, use the device manufacturer’s actual draw and keep extra reserve. For camping and van life, consider how often you can recharge. Check the current price on Amazon, confirm the port layout before ordering, and use our CPAP guide or our van-life guide for the next decision.

Every model mentioned, at a glance

Manufacturer specifications and Amazon buyer ratings

Model ↕	Score / 10 ↕	Wh ↕	Output W ↕	LiFePO4 ↕	Cycles ↕	Solar input W ↕	Weight (lb) ↕	Rating ↕	Value for its size	Availability
BLUETTI AC180 Best overall	8.2	1,152	1,800	Yes	See listing	500	See listing	4.51,900 ratings	Excellent value	Check price on Amazon →
Anker SOLIX C1000	6.2	1,056	See listing	Not stated	See listing	600	See listing	4.72,100 ratings	Good value	Check price on Amazon →
Jackery Explorer 300	5.2	292	See listing	Not stated	See listing	See listing	See listing	4.611,300 ratings	Fair value	Check price on Amazon →
Anker SOLIX C300 Best lightweight	4.5	288	See listing	Not stated	3000	100	See listing	4.61,900 ratings	Premium price	Check price on Amazon →
Anker SOLIX 521	5.5	256	300	Yes	See listing	See listing	See listing	4.43,100 ratings	Premium price	Check price on Amazon →
Jackery Explorer 1000 v2	5.9	1,024	See listing	Yes	4000	See listing	25	4.73,700 ratings	Premium price	Check price on Amazon →

Specifications as stated in the Amazon listing. Missing details: see listing. Scores use specifications and buyer ratings. How we rank.

Frequently asked questions

How many watt-hours do I need for a power outage?

Add the watt-hours for your essential devices over the number of outage hours, then divide by 0.85 and add a 20–30% reserve. A router, lights, phones and laptop may fit below 1,000Wh, while adding a refrigerator can push you into the 1,000–1,200Wh range or higher. Check appliance startup wattage as well as running consumption.

How long will a 1,000Wh power station run?

Using the planning formula, a 1,000Wh station provides about 850Wh through an AC outlet. That equals roughly 8.5 hours at 100W, 14.2 hours at 60W, or 2.8 hours at 300W. Actual runtime varies with device cycling, inverter behavior and operating modes. Several devices share the same energy reserve, so add their wattages together.

Is 300Wh enough for camping?

A 300Wh-class station is suitable for phones, lights, camera batteries, a router and limited laptop use. It is less suitable for cooking, heating or continuous refrigeration. At 100W, the 85% planning estimate gives roughly 2.5 hours. For several days, keep loads low, recharge when possible and use the 20–30% reserve rather than draining the battery completely.

How many watt-hours do I need for a CPAP?

Use the CPAP manufacturer’s wattage and multiply it by your planned hours of sleep. Add separate consumption for heated humidity or a heated hose if enabled, then apply the 85% rule and a 20–30% reserve. Because settings and accessories vary, there is no universal Wh answer. A battery with more capacity gives useful protection against a longer night or uncertain draw.

What is the difference between watts and watt-hours?

Watts measure the rate of electrical power at a moment in time. Watt-hours measure stored or consumed energy over time. A 100W appliance running for 3 hours uses about 300Wh. A power station’s inverter must support the appliance’s watts, while its battery must contain enough watt-hours for the total runtime. You need both figures when sizing.

Should I buy more watt-hours than my calculation requires?

Yes, in most cases. Estimates are rarely perfect, and AC conversion uses energy, while motors may have startup demands. Add 20–30% to your device total, then account for approximately 85% practical battery availability. Extra capacity also lets you charge another phone or run a light without sacrificing your primary emergency load. Avoid paying for excess size if your use is strictly occasional and low-wattage.