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Calculate Backup Runtime
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Calculate Required Battery Capacity
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Calculate Optimal UPS Size
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Total Load Calculator
Calculate total power requirements from multiple devices
Common Devices
Load Summary
How to Use the Power Backup Calculator
Backup Runtime Calculator
Determine how long your backup system will sustain your load. Enter battery capacity (Ah), voltage (V), power consumption (W), and efficiency percentage. Get runtime in hours and hours:minutes:seconds format.
Battery Capacity Calculator
Find the battery size you need for specific backup duration. Enter required time, power consumption, voltage, and efficiency. Get recommended capacity with cost estimates and configuration suggestions.
UPS Sizing Calculator
Calculate optimal UPS rating for your needs. Input maximum power, backup duration in minutes, efficiency, and safety margin. Get VA rating, energy requirements, and cost estimates.
Load Calculator
Add up total power consumption from all your devices. Enter individual device wattages and get total load, average per device, and recommended UPS size for 2-hour backup.
Understanding Power Backup Systems
What is Power Backup?
Power backup systems (UPS, batteries, generators) provide emergency power when the main supply fails. They protect against data loss, equipment damage, and service interruption. Proper sizing ensures adequate runtime for your critical loads.
Key Formulas
- Runtime (hours) = (Capacity × Voltage × Efficiency) / Power
- Required Capacity = (Power × Time × 1.2) / (Voltage × Efficiency)
- UPS VA = Power × 1.2 (with 20% buffer)
- Battery Energy (Wh) = Capacity (Ah) × Voltage (V)
Battery Types
- Lead-Acid: Affordable (~$50/kWh), requires maintenance, ~500-1000 cycles
- AGM: Sealed, maintenance-free (~$60/kWh), ~500-1200 cycles
- Lithium-ion: Compact (~$300/kWh), ~3000-5000 cycles, no maintenance
- LiFePO4: Safest lithium (~$200/kWh), ~4000-6000 cycles, excellent for deep cycling
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Frequently Asked Questions
How long will my battery last?
Runtime = (Capacity in Ah × Voltage × Efficiency) / Power in W. Example: 100Ah 12V battery with 500W load at 85% efficiency = 2.04 hours.
What size UPS do I need?
UPS VA = Total Power × 1.2 (with 20% buffer). For 1000W load, get 1200VA UPS minimum. Always round up to next standard size.
Why add a safety buffer?
20-30% buffer prevents overloading, extends equipment lifespan, accounts for device upgrades, and handles temporary power spikes.
Lead-acid or Lithium batteries?
Lead-acid is budget-friendly but heavy; Lithium is expensive but compact and lasts 5x longer. Choose based on budget and space constraints.
What is system efficiency?
Efficiency (85-95%) is the percentage of battery energy usable by devices. Rest is lost in inverters and wiring. Higher efficiency = longer runtime.
How many devices can a UPS support?
Depends on total wattage. Add up all devices' power consumption and ensure UPS VA rating exceeds total. Most home UPS support 3-5 devices.