# How to Read a PCS / BESS Datasheet: 8 Parameters That Decide Sizing Don’t memorise every row. Focus on the 8 parameters that decide selection: power, battery voltage window, DC current, grid/off-grid, overload, efficiency, THD/PF, IP/temp/altitude. Focus on the 8 selection-defining parameters **Rated power kW/kVA**—peak vs continuous load. **Battery voltage window V**—must cover the battery’s operating range. **Max DC current A**—battery-side current capability; easier to hit the limit at low voltage. **Grid-tied/off-grid ability**—backup/microgrid readiness; check STS and switching time. **Overload**—motor/inrush adaptation; 1.5× overload is a key advantage (e.g. [SP125HCPS](/en/product/sp125hcps)). **Efficiency**—losses and thermal; VGRID plug-in PCS reach 98%+. **THD / PF**—power quality; lower THD is better, PF -1~1. **IP / temperature / altitude**—environment fit; watch derating outdoors/high altitude. Note PCS datasheets often rate in kVA; at PF≈1, kW≈kVA. Confirm with the specific model’s datasheet. ## How to convert kW and kVA? At PF≈1, kW≈kVA; with inductive loads kVA>kW, so leave margin by power factor. ## Why is the battery voltage window important? It decides compatibility with your battery; the high/low bounds must cover the operating range. ## What is 1.5× overload for? Motors/pumps have high inrush; 1.5× short-term overload avoids tripping and improves load adaptability. ## How does altitude affect a PCS? Thin air reduces cooling and insulation; follow the derating curve and keep margin.