Surviving Stage 6: Enterprise UPS Sizing Guide
In the South African context, a Uninterruptible Power Supply (UPS) is no longer just for conditioning power—it's a primary business continuity device. With Stage 6 load shedding necessitating 4-hour runtime windows, the traditional "10 minutes to shutdown" sizing rule is obsolete.
The Power Triangle: kVA vs kW
One of the most common mistakes in procurement is confusing Apparent Power (kVA) with Real Power (kW). Your server power supplies are rated in Watts.
Example: A 10kVA UPS with a 0.8 pf can only support 8kW of load. Always spec based on kW capacity.
Battery Chemistry: Lead Acid (VRLA) vs Lithium-Ion
For decades, VRLA was the standard. However, Stage 4+ load shedding kills VRLA batteries rapidly because they require 8-10 hours to recharge fully. Frequent deep discharging reduces their lifespan to <18 months.
- Lithium-Ion (LiFePO4): Can recharge in 2 hours, supports 2000+ cycles at 80% Depth of Discharge (DoD), and has a lower TCO over 5 years.
- Recommendation: For any runtime requirement over 30 minutes, Lithium-Ion is now the financially prudent choice.
Sizing for 4-Hour Runtime
To survive a 4-hour block, you need massive battery capacity relative to the inverter. We recommend Eaton 9PX or APC Smart-UPS On-Line series with extended battery modules (EBMs).
Rule of Thumb: Calculate your average load (not peak). If your rack draws 2000W steady state, you need roughly 9kWh of battery capacity to survive 4 hours safely (allowing for efficiency losses).
The Solar Integration
For extended outages, a hybrid inverter approach is superior to a pure UPS. Integrating a SunSynk or Victron commercial inverter allows you to blend grid, generator, and solar power, reducing diesel costs during daylight outages.