How long can I keep working 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.

The ThinkPad T480 has two batteries: a built-in front pack and a swappable rear pack. Lenovo's spec sheet lists: optional internal 24 Wh + swappable rear 24/48/72 Wh. So a T480 has 24 to 96 Wh in total, depending on which packs are fitted. With 24 Wh internal + 24 Wh rear at 80% health doing office work (about 8 W), it lasts roughly 4.6 hours. These are estimates; heavy work drains it faster.

The MacBook Air M1 (2020) has a 49.9 Wh battery and is very efficient: about 4 W on light office work and 7 W on video calls (typical figures). At 80% battery health that is roughly 9.5 hours of office work or 5.4 hours of calls — enough for most load-shedding spells without a power bank.

Type your laptop model in the calculator above — we list the factory battery options for 275 models with a link to the maker's spec sheet. You can also read the Wh printed on the battery label, or run the free Battery Health Analyzer report on Windows, which shows both the design capacity and the capacity your battery holds today.

Pick the closest laptop type (ultrabook, business, gaming, MacBook Air or MacBook Pro) under "My model isn't listed". The calculator then uses a typical battery size and power draw for that type. If you know your battery's Wh from its label, type it in for a better answer.

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.

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.

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.

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.

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.

A laptop already has its own battery, so it usually needs no UPS. What load-shedding really takes away is the Wi-Fi: put the router and ONU on a small DC mini UPS first. A home inverter with a battery is the choice if you also want a fan and lights. Use the calculator's inverter option to see how many hours your battery gives for your total load.

Check your laptop charger label first. If it says USB-C and 45 W to 65 W, a USB-C PD power bank with at least that PD output works for most ultrabooks and business laptops. Match or exceed the watts, and pick the capacity from the calculator's fix suggestion. Laptops with a round barrel charger need a different solution, so ask us on WhatsApp with your model.

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.

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.