Backup Power Sizing Calculator
List your critical loads and desired runtime. We'll recommend a UPS/inverter rating and battery bank configuration using standard sizing engineering — not a rule of thumb.
1. Critical loads
Add every device that must stay powered — servers, switches, aircon, lighting, security. Presets below prefill typical wattages; edit freely.
2. Runtime & system
Advanced assumptions
Recommended system
Backup Power Spec
Total load
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UPS / Inverter
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Battery bank
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Usable energy
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Indicative budget
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Equipment only, excl. installation, cabling & VAT. See methodology below.
How this is calculated
Required apparent power = total watts ÷ power factor, then increased by your safety margin to cover motor/compressor inrush, rounded up to the nearest standard commercial rating.
Usable battery energy = (total watts × runtime) ÷ inverter efficiency, then divided by depth-of-discharge to get nominal battery capacity (lithium safely discharges deeper than lead-acid/AGM).
Reference unit pricing: 5kW inverter and 100Ah AGM / 3.55kWh lithium battery units, priced off published South African market rates (Sept 2026). Confirm current SNRG Corporate pricing before ordering.