How Long Will a 1kWh Battery Last?
ZacharyWilliamUpdated: December 23, 2025
A 1kWh (1,000Wh) battery can last anywhere from minutes to days—it depends on your load (watts) and how you’re using the battery (AC inverter vs. DC/USB). The fast way to estimate runtime is:
Runtime (hours) ≈ Usable watt-hours ÷ Total watts
Example: A 100W device on a 1kWh battery → about 10 hours (ideal). In real life, AC use is often a bit lower due to conversion losses.
What “1kWh” actually means
kW is power (how fast you’re using electricity). kWh is energy (how much electricity you used over time). A helpful way to think about it: 1kWh = 1,000 watts for 1 hour (or 100W for 10 hours, 50W for 20 hours, etc.). See a quick explanation here: kW vs. kWh (Aurora Solar) and here: kW vs. kWh (Vanguard Power).
The runtime formula (and what “usable” means)
The clean math is: Hours = Battery Wh ÷ Load W
But in real life, you usually want usable watt-hours:
Runtime (hours) ≈ (Battery Wh × Efficiency factor) ÷ Load W
- AC outlets: common planning range is roughly 0.80–0.90 due to inverter + system losses (varies by model and load).
- DC/USB outputs: often more efficient than AC (less conversion).
If you’re comparing different products, always check both capacity (Wh) and output rating (W). A 1kWh battery can’t help if the inverter/output can’t supply your device’s watts or startup surge.
1kWh runtime cheat sheet (table)
Below are quick estimates for a 1,000Wh battery powering a continuous load. “Typical AC usable” uses an easy planning factor of 85% (0.85). Your real number may be higher or lower.
| Continuous Load (W) | Ideal Runtime (1000Wh ÷ W) | Typical AC Usable (850Wh ÷ W) | What this feels like |
|---|---|---|---|
| 10W | 100.0 hrs | 85.0 hrs | Wi-Fi router, small LED lighting |
| 20W | 50.0 hrs | 42.5 hrs | Two small devices, light + router |
| 40W | 25.0 hrs | 21.3 hrs | CPAP (basic settings), fan on low |
| 60W | 16.7 hrs | 14.2 hrs | Laptop class load |
| 100W | 10.0 hrs | 8.5 hrs | TV or multiple small electronics |
| 150W | 6.7 hrs | 5.7 hrs | Desktop + monitor, small cooking bursts |
| 200W | 5.0 hrs | 4.3 hrs | Projector, small tools, heavier loads |
| 300W | 3.3 hrs | 2.8 hrs | Blender, small microwave bursts (if supported) |
| 500W | 2.0 hrs | 1.7 hrs | Appliance class load |
| 800W | 1.25 hrs | 1.06 hrs | Coffee maker / toaster class (if within output) |
| 1000W | 1.0 hr | 0.85 hr | Near the limit for many 1kWh stations |
| 1200W | 0.83 hr | 0.71 hr | Only if your inverter is rated for it |
| 1500W | 0.67 hr | 0.57 hr | Often exceeds many 1kWh-class inverters |
Tip: many household appliances are not continuous loads. Fridges, for example, cycle on/off; watts shown on labels can be misleading for “hours of cooling.”
Common devices: realistic runtimes
Use this section when you’re asking questions like: “Will 1kWh run my fridge?” or “Can 1kWh power my CPAP overnight?” For appliance energy estimation guidance (including how cycling affects usage), see: U.S. Department of Energy: Estimating Appliance and Home Electronic Energy Use.
| Device (typical) | Typical Power / Notes | Ideal Hours on 1kWh | Typical AC Plan (≈85%) |
|---|---|---|---|
| Wi-Fi router | ~10–15W (often continuous) | 67–100 hrs | 57–85 hrs |
| LED light | ~8–12W per bulb | 83–125 hrs | 71–106 hrs |
| Laptop | ~45–90W while charging/working | 11–22 hrs | 9–19 hrs |
| TV (LED) | ~60–150W depending on size/brightness | 6.7–16.7 hrs | 5.7–14.2 hrs |
| CPAP (no heated humidifier) | Often ~30–60W; heated humidifier can increase draw a lot | 16.7–33.3 hrs | 14.2–28.3 hrs |
| Mini fridge (average) | Often ~60–120W average (cycles) | 8.3–16.7 hrs | 7.1–14.2 hrs |
| Full-size refrigerator (label watts are not “all day” watts) | Many fridges are cited around ~300–800W when the compressor is running, but they cycle on/off. | Varies widely | Varies widely |
| Coffee maker / toaster | ~800–1200W (short bursts) | 0.8–1.25 hrs | 0.7–1.06 hrs |
For motors and compressors (fridges, pumps), always account for startup surge. Your battery may have the energy, but your inverter must handle the surge watts.
3 real-world 1kWh plans (overnight, WFH, outage)
Plan A: CPAP overnight + phone + a light
- CPAP: 40W × 8 hrs = 320Wh
- LED light: 10W × 4 hrs = 40Wh
- Phone charging: ~15Wh
Total ≈ 375Wh (before losses). A 1kWh battery can usually cover this comfortably, especially if you keep everything on efficient outputs and avoid heated CPAP humidification.
Plan B: Work-from-home essentials
- Laptop average: 60W × 6 hrs = 360Wh
- Wi-Fi: 12W × 6 hrs = 72Wh
- Monitor: 50W × 6 hrs = 300Wh
Total ≈ 732Wh. This is where AC conversion losses start to matter—using DC/USB-C where possible can help.
Plan C: Short outage “keep food safe” strategy
A fridge is not a steady 300–800W all day—it cycles. DOE’s guidance explains why estimating “hours” is tricky for cycling loads (source).
- Best practice: keep the door closed, chill bottles of water ahead of time, and run the fridge in intervals.
- Practical takeaway: 1kWh can often support several hours to part of a day of refrigeration depending on efficiency, ambient temp, and door openings.
When 1kWh won’t feel like much
High-wattage heat devices burn through energy fast:
- Space heater: 1,500W → under 1 hour (and many inverters can’t supply it)
- Electric kettle: 1,200–1,800W → ~30–50 minutes
- Microwave (full-size): often 1,000W+ input → about 1 hour or less
Why your result may differ from the math
- AC inverter losses: converting battery DC to household AC costs energy, especially at very low or very high loads.
- Device behavior: compressors cycle, chargers taper, and “nameplate watts” aren’t always real-time watts.
- Surge loads: startup surges can trip the inverter even if the average watts look fine.
- Temperature: cold weather can reduce available energy for lithium batteries.
- Battery age: capacity declines with cycles and calendar time.
If you want the most accurate estimate, measure your real draw with a plug-in power meter (for AC devices), then run the calculation using that measured wattage.
How to make a 1kWh battery last longer
- Prefer DC/USB outputs for electronics when possible (skip the AC inverter step).
- Bundle loads intelligently: do “high draw” tasks in short sessions (coffee, blending) and keep essentials low and steady.
- For fridges: keep doors closed, pre-chill, and avoid frequent cycling from door openings (DOE guidance helps explain cycling impacts).
- Turn off idle outputs (some power stations draw a small amount just keeping AC “on”).
- Right-size your inverter: don’t buy capacity without enough output rating and surge headroom.
A practical example: UDPOWER S1200 (1,190Wh class)
If you’re shopping for “about 1kWh,” it can be smart to choose a bit more capacity so real-world losses don’t surprise you. One example is the UDPOWER S1200, which is in the ~1kWh+ class at 1,190Wh—roughly 19% more energy than a 1,000Wh pack on paper.
| Spec (from UDPOWER) | What it means for “how long will it last?” |
|---|---|
| Capacity: 1,190Wh | At the same load, expect ~19% longer runtime vs. 1,000Wh (before losses). |
| AC output: 1,200W rated (up to 1,800W max / surge) | Helps with appliances that need higher running watts or startup surges (within limits). |
| Solar input: 12V–75V, 12A, 400W max | Supports meaningful solar recharge so you can extend runtime during multi-day use. |
| AC input: 800W max; fast charge: 0–100% ~1.5 hours (lab reference) | Faster recharge can matter more than extra capacity if outages are short and you can top up quickly. |
| Battery chemistry: LiFePO4; cycle life: 80%+ after 3000 cycles (listed) | LiFePO4 is commonly chosen for longevity and stability in portable power stations. |
Note: many brand runtime charts use ideal math (Wh ÷ W). Real-world results vary with inverter efficiency, temperature, and device behavior. UDPOWER also lists example runtimes on the S1200 page (for instance, TV at 100W shown as 11.9 hours and CPAP at 40W shown as 29.7 hours).
FAQ
How long will a 1kWh battery last at 100W?
Ideal math: 1,000Wh ÷ 100W = 10 hours. Planning for typical AC losses (~85%): closer to 8.5 hours.
How long will a 1kWh battery last at 500W?
Ideal: 2 hours. Typical AC planning: ~1.7 hours.
Will a 1kWh battery run a refrigerator?
Often, yes—for a while. The hard part is that fridges cycle and have startup surges. Check (1) running watts, (2) surge watts, and (3) real daily energy use. DOE’s guidance on estimating appliance energy use is a good starting point: Energy.gov.
Is 1kWh the same as “a 1,000W battery”?
Not exactly. 1kWh is energy. 1,000W is power (output rate). A battery can have 1kWh of energy but still need a big enough inverter/output rating to run a 1,000W device.
Why does my power station show less than 1kWh delivered?
AC inversion, internal electronics, cable losses, and device behavior can reduce delivered energy compared to the battery’s rated Wh.
Does using USB-C instead of AC really help?
Often yes. Skipping DC→AC→DC conversions can reduce losses for phones, tablets, and laptops.
How do I estimate runtime for multiple devices at once?
Add their watts together, then divide usable Wh by total watts. Example: (60W laptop + 12W router) = 72W total.
What’s the quickest way to get a trustworthy number?
Measure real draw with a power meter, then use the formula with an efficiency factor if you’re running through AC.
Sources (linked)
- U.S. Department of Energy (Energy Saver): Estimating Appliance & Home Electronic Energy Use — energy.gov
- kW vs. kWh explanation — Aurora Solar / Vanguard Power
- Refrigerator wattage discussion (contextual, varies by model) — EnergySage
- UDPOWER S1200 product specifications — UDPOWER official page
Disclosure: Runtime examples are estimates for planning. Always confirm your device’s actual wattage and surge needs (nameplate or measured), and follow your power station’s operating guidelines.
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