When the power drops at a home office, the questions arrive in a fixed order. Will the internet stay up? How long will the laptop last? Will the battery make it to the end of the working day, or to tomorrow morning? This calculator answers all three for a portable power station. It is meant for remote staff deciding what to buy, office managers equipping the few people who must keep working, and continuity planners who need a defensible figure for a home working standard.
How the calculator works
Each device gets one line, and its daily energy is:
Daily energy (Wh) = watts × quantity × hours per day (capped at 24)
The tool adds those lines for the day's total, and adds the wattages for the peak, the draw with everything switched on at once. It then works out how much of the battery reaches your devices:
Usable energy (Wh) = rated capacity (Wh) × efficiency
From there come three answers:
- Runtime at peak (hours) = usable Wh ÷ peak watts
- Days covered = usable Wh ÷ daily Wh
- Capacity needed (Wh) = daily Wh × days ÷ efficiency
Rated capacity is the watt-hour figure on the spec sheet. Efficiency covers what the inverter and battery lose when you draw AC power: 85 percent is a fair default for current lithium iron phosphate (LiFePO4) units, 80 percent safer for an older or smaller one. Continuous output is the station's AC watt rating; a higher peak is flagged as an overload, since the station would cut its outlets. Days is how long the plan has to last: one for a working day, two or three for a storm weekend. Take wattages from the device label or, better, a plug-in power meter.
Worked example
The calculator opens with a home office on a 1 kWh class station: 1,070 Wh rated, 1,500 W continuous output, 85 percent efficiency, planned for one day. Those defaults match the published specs of the Jackery Explorer 1000 v2. The loads are a Wi-Fi router at 12 W for 24 hours (288 Wh), a modem at 10 W for 24 hours (240 Wh), a laptop at 60 W for 8 hours (480 Wh), an LED lamp at 10 W for 6 hours (60 Wh) and phone charging at 10 W for 3 hours (30 Wh).
- Peak draw: 12 + 10 + 60 + 10 + 10 = 102 W, far below the 1,500 W output, so no overload.
- Daily energy: 288 + 240 + 480 + 60 + 30 = 1,098 Wh.
- Usable energy: 1,070 × 0.85 = 909.5 Wh, shown as 910 Wh.
- Runtime with everything on at once: 909.5 ÷ 102 = 8.9 hours, about 8 h 55 min.
- Days covered: 909.5 ÷ 1,098 = 0.83 days.
- Capacity needed for one day: 1,098 ÷ 0.85 = about 1,292 Wh.
So the station carries a full working day of laptop use but runs dry before the next morning, about 188 Wh short. The router and modem draw only 22 W between them, yet running around the clock they use 528 Wh, almost half the day. Powering them from the station's 12 V or USB-C outputs skips most of the inverter loss, and cutting the laptop's day to four hours brings the total to 858 Wh, which the same station covers (1.06 days).
What the numbers leave out
- Start-up surges. Peak watts is the sum of running watts; compressors and pumps draw several times that for a moment at start-up. For motor loads, use the generator size calculator.
- Inverter idle draw. With the AC outlets on, the inverter uses power even with nothing plugged in. At 15 W of idle draw, that is 360 Wh a day. Turn AC off when only DC ports are in use.
- Cold. Lithium cells deliver less in the cold, and many LiFePO4 stations will not charge below freezing (32°F, 0°C) unless they have self-heating.
- Ageing. Makers commonly quote several thousand cycles before a LiFePO4 pack falls to 70 or 80 percent of new; after a few years, plan with the lower number.
- Switchover. Some stations offer a UPS mode; check its switchover time before trusting a desktop PC to it, or use a conventional UPS.
Choosing a station in this size class
A unit of about 300 Wh keeps a router and modem alive overnight, around 11 hours at 22 W. The 1 kWh class carries one person's working day, as the example shows, or the router and modem alone for about 41 hours. For a full day and night without recharging, or two people, step up to the 2 kWh class: 2,042 Wh rated gives about 1,736 Wh usable, or 1.58 days of the example load. Past that, an expandable system with add-on batteries usually beats one large box, and a way to recharge from solar or a vehicle matters more than raw capacity. Whatever the size, look for LiFePO4 chemistry, a pure sine wave inverter and a wall recharge quick enough to refill the unit between outages.
These stations were not bench tested by us. The shortlist rests on spec sheets from the makers and published reviews, so confirm capacity, output and recharge time on the current listing.
Readiness kit
| Category | Pick | Why it is on the list | Link |
|---|---|---|---|
| Power station, small | Jackery Explorer 300 | A light unit of about 290 Wh for a go-bag, a router and a few phone charges. | Shop on Amazon |
| Power station, 1 kWh | Jackery Explorer 1000 v2 | About 1 kWh of LiFePO4 storage and a 1,500 W inverter: a laptop, router, phone chargers and a lamp through a full working day. | Shop on Amazon |
| Power station with UPS mode | Anker SOLIX C1000 | 1 kWh LiFePO4 with a pass-through UPS mode, so a desk setup keeps running when the mains drops. | Shop on Amazon |
| Power station, 2 kWh | Jackery Explorer 2000 v2 | Twice the storage of the 1 kWh class for a home office that has to last a full day off grid. | Shop on Amazon |
| Power station, expandable | EcoFlow DELTA and RIVER stations | Fast AC recharging, and the larger DELTA units take add-on batteries when a site needs more hours. | Go to EcoFlow |
For the wider picture of a home worker in a regional outage, see continuity planning for hybrid work and the extreme heat and grid stress playbook.
Sources
- U.S. Department of Energy, Energy Saver: "Estimating Appliance and Home Electronic Energy Use" (wattage × hours per day).
- Ready.gov: Power Outages
- CDC: What to Do to Protect Yourself During a Power Outage
- Manufacturer spec sheets and manuals (Jackery, Anker SOLIX, EcoFlow) for capacity, output, cycle life and charging temperatures.
Frequently asked questions
How long will a 1,000 Wh power station run a router and modem?
At a combined 22 W and 85 percent efficiency, a 1,070 Wh station runs a typical router and modem for about 41 hours. Feeding them from the DC outputs instead of the AC inverter stretches that further.
Why does the calculator use less than the rated capacity?
Rated capacity is what the battery stores, not what reaches your devices. The inverter and wiring lose energy on the way to 120 V AC, so the tool multiplies by your efficiency figure, 85 percent by default. A 1,070 Wh station therefore delivers about 910 Wh at the outlets.
Can a power station replace a UPS for a desktop computer?
Only if its UPS or pass-through mode switches fast enough for your computer's power supply, and that varies by model. A UPS is built for the switchover; a power station is built for hours of runtime. Many home offices use both.
How much capacity do I need for a weekend?
Multiply your daily watt-hours by the number of days and divide by the efficiency. For the example office, 1,098 Wh a day for two days at 85 percent comes to about 2,584 Wh, more than a single 2 kWh class station holds. Trim the always-on loads or plan to recharge.