Battery Runtime Calculator
See how long your existing battery will run your load.
Step-by-step landing pages for this calculator — pre-filled loads and FAQs.
- Use-case guideBackup for 500W LoadA ~500 W essential load (2 fans, fridge, TV, lights, router) for 4 hours needs about 2.3 kWh — typically 12V 200Ah LiFeP…
- Use-case guideHome Office Backup PowerWork-from-home setups need laptop, monitor, router, and often a fan running 4–6 hours per outage.
- Pillar guideHome Backup Power GuideInverters, lithium UPS, and load shedding strategies for Pakistani homes.
75W per unit × 2 = 150W for this row
What this calculator does
Works backward from your existing or planned battery to estimate runtime at a given load.
How calculations work
- Add appliances from the Pakistan household and business list, or enter custom wattage.
- Set quantity and required backup hours (typical load shedding window: 2–6 hours).
- We calculate total load (W), energy needed (Wh), and recommended voltage and Ah using depth-of-discharge for your battery type.
- Inverter/UPS VA suggestion includes a 40% headroom factor for motor and surge loads.
Examples
≈75+75+250+12 = 412 W → ~1,900 Wh → 12V 200Ah LiFePO4 class bank for essentials during evening outages.
≈50+120+80 W × 8 h → consider 24V lithium for efficiency on longer commercial backup.
Common mistakes
- Using nameplate watts for fridges and AC without duty-cycle (use average draw or our presets).
- Ignoring inverter efficiency (we add ~15% margin on Wh).
- Sizing lead-acid to 100% depth of discharge — use 50% DoD for flooded/tubular.
FAQs
Relevant landing pages
Dedicated guides with pre-filled calculator settings for common Pakistani setups.
Backup for 500W Load
A ~500 W essential load (2 fans, fridge, TV, lights, router) for 4 hours needs about 2.3 kWh — typically 12V 200Ah LiFeP…
Home Office Backup Power
Work-from-home setups need laptop, monitor, router, and often a fan running 4–6 hours per outage.
Home Backup Power Guide
Inverters, lithium UPS, and load shedding strategies for Pakistani homes.