How long can I keep working during load-shedding?
Pick your laptop, what you are doing and your outage length. We work out how many minutes your laptop and your Wi-Fi router will last on battery, power bank, mini UPS or inverter — and what to fix if they fall short. Free, no signup, runs in your browser.
Laptop
4 h 12 min
Covers your outage (2 h)
Estimated draw ~8.7 W · usable battery 36 Wh
Internet (router + ONU)
0 min
No backup — Wi-Fi dies the moment the light goes
15 W on no backup
Weakest link: your internet (router)
Even with laptop battery left, you go offline first.
How to fix it
- Put the router and ONU on a DC mini UPS. For 2 h at 15 W you need about 36 Wh (around 10,000 mAh at 3.7 V). Check that its 9 V / 12 V output matches your router's adapter label. Ask us on WhatsApp
Monthly electricity cost of this laptop
Rs 60/unit is only an example, not an official tariff. Use the per-unit rate printed on your own electricity bill (it changes with slab, taxes and FPA).
About 2.1 units (kWh) a month ≈ Rs 123 for this laptop at the same workload, including ~12% charger loss.
Show the formulas used
- Laptop draw = workload watts + screen watts × brightness (typical values, see table below) = 8.7 W.
- Usable battery = 48 Wh × 80% health × 95% (laptops shut down near 5%) = 36.5 Wh.
- Battery-only runtime = usable Wh ÷ draw W × 60 = 4 h 12 min.
- Power bank Wh = mAh × 3.7 V ÷ 1000 × 85% conversion efficiency. If the PD output is lower than the draw, the laptop battery covers the gap.
- Mini UPS runtime = mAh × 3.7 V ÷ 1000 × 85% ÷ router+ONU watts.
- Inverter usable Wh = V × Ah × usable depth × inverter efficiency. Laptop on the UPS counts its charger loss (÷ 0.88).
- Monthly units = draw ÷ 0.88 × hours × days ÷ 1000; cost = units × your rate.
Real results vary ±20-30% with model, battery age, heat and background apps. Treat this as a planning estimate, not a guarantee.
How the calculator works
Runtime is simply usable energy (Wh) ÷ power draw (W). The tricky part is getting honest numbers for both sides. For energy, we take your battery size, multiply by battery health, and keep 95% because laptops shut down before reaching zero. Power banks lose about 15% converting their 3.7 V cells up to USB-C voltage, mini UPS units lose about 15%, and home inverters typically lose 15-20%. Lead-acid and tubular batteries should only be used to about 50% depth to stay healthy, while lithium packs can go to around 80%.
For power draw, we use typical average figures for each laptop type and workload, plus the screen, which scales with brightness. If your power bank's USB-C PD output is lower than what the laptop needs (common when gaming or editing), the bank only slows the drain and the laptop battery covers the rest — the calculator models that too.
The laptop and the internet are checked separately, because in most Pakistani homes the router dies first. The result tells you which one is your weakest link and how much extra capacity you would need.
Typical laptop power draw (approximate)
Typical average watts on battery at about 60% brightness. Your exact model can be 20-30% higher or lower.
| Laptop type | Typical battery | Browsing / office work | Coding / many tabs | Zoom / Teams video calls | Video editing / rendering | Gaming |
|---|---|---|---|---|---|---|
| Ultrabook / thin & lightDell XPS 13, HP Envy, ZenBook | ~50 Wh | ~7 W | ~9 W | ~11 W | ~22 W | ~30 W |
| Business 14-15"ThinkPad T/L, Latitude, EliteBook, ProBook | ~48 Wh | ~9 W | ~11 W | ~13 W | ~27 W | ~35 W |
| Gaming laptopLegion, TUF, Nitro, Victus, Omen | ~60 Wh | ~18 W | ~22 W | ~26 W | ~64 W | ~94 W |
| MacBook Air (M1-M3)MacBook Air 13" / 15" | ~52 Wh | ~5 W | ~7 W | ~9 W | ~17 W | ~20 W |
| MacBook Pro (M-series)MacBook Pro 14" / 16" | ~70 Wh | ~9 W | ~11 W | ~13 W | ~32 W | ~42 W |
Typical watts of other backup devices (approximate)
| Device | Typical draw | Usually backed up by |
|---|---|---|
| Wi-Fi router | 6-12 W | DC mini UPS or inverter |
| Fibre ONU / modem box | 5-8 W | DC mini UPS or inverter |
| Phone charging | 5-18 W while charging | Home inverter / UPS |
| LED bulb | 9-18 W | Home inverter / UPS |
| Ceiling fan on UPS | 60-90 W (AC), 30-40 W (DC/inverter fan) | Home inverter / UPS |
Quick ways to stretch your backup
- • Lower the brightness — the screen is often a third of the total draw on light work.
- • Use Windows "Best power efficiency" or macOS Low Power Mode during the outage.
- • Close heavy apps — a browser with 40 tabs or a game launcher in the background can double the draw.
- • Put the router on a DC mini UPS so you stay online. Match its 9 V / 12 V output to your router's adapter label.
- • Keep the laptop battery healthy — check it with the Battery Health Analyzer, and see battery replacement cost in Pakistan if it is worn.
- • Need a power bank, adapter or cable? See our laptop power banks, browse laptop accessories, or WhatsApp us at 0314 4000131.
Frequently asked questions
How long does a laptop battery last during load-shedding?
It depends on battery size, battery health and what you are doing. A typical business laptop with a 48 Wh battery at 80% health doing office work draws about 8-9 W, so it lasts roughly 4 to 4.5 hours. The same laptop on a video call lasts closer to 3 hours, and gaming can empty it in about an hour. Use the calculator above with your own numbers.
Can a power bank charge my laptop during load-shedding?
Yes, if your laptop charges over USB-C and the power bank supports USB-C Power Delivery (PD) at enough watts. A 45-65 W PD output suits most ultrabooks, MacBook Airs and business laptops. Older laptops with a round barrel charger and most gaming laptops cannot run fully on a normal power bank. A 20,000 mAh bank holds about 74 Wh, and around 85% of that reaches the laptop.
How do I convert power bank mAh to Wh?
Multiply mAh by the cell voltage (3.7 V) and divide by 1000. So 20,000 mAh × 3.7 ÷ 1000 = 74 Wh. Do not use the 5 V or 20 V output voltage for this — the mAh printed on a power bank is measured at the 3.7 V cell level.
Why does my Wi-Fi go off before my laptop battery runs out?
Because the router and fibre ONU have no battery of their own. Unless they are on a mini DC UPS or a home inverter, the internet stops the moment the light goes, even if your laptop still has hours left. A Wi-Fi router plus ONU usually draws about 10-18 W in total.
How long will a 10,400 mAh mini UPS run my router?
10,400 mAh × 3.7 V ≈ 38 Wh. After about 15% conversion loss, roughly 33 Wh is usable. A router and ONU drawing 15 W together would run for a little over 2 hours. A router alone at 9 W would run for about 3.5 hours. Real results vary with the model and the age of the cells.
How long will my inverter or UPS battery run a laptop and fan?
Usable energy is battery voltage × Ah × usable depth × inverter efficiency. A 12 V 100 Ah lead-acid battery used to 50% with an 82% efficient inverter gives about 490 Wh. A laptop (about 10 W from the wall) plus a 75 W ceiling fan and a router is about 100 W, so that is roughly 5 hours. Without the fan it would be many hours.
Does battery health really change my backup time?
Yes, directly. A battery at 60% health holds only 60% of its original energy, so runtime drops by the same share. Check your health with our free Battery Health Analyzer. If it is low, a replacement battery is often the cheapest way to get your load-shedding backup back.
How much electricity does a laptop use per month?
Most laptops use very little. A laptop drawing about 10 W for 8 hours a day, 26 days a month, uses around 2-2.5 units (kWh). Multiply by the per-unit rate on your own bill to get the cost. Gaming laptops under heavy load can use several times more.
All figures are typical or approximate planning estimates, not measurements of any specific model. The electricity rate in the tool is an editable example, not an official tariff.