BESS Round-trip Carbon Cost Calculator

Why BESS carbon accounting matters

Every charge/discharge cycle wastes energy as heat in the battery, inverter, and wiring. That wasted kWh still came from somewhere—if the grid, it carries a carbon tag. Storage is only as green as the electrons you put in.

Round-trip loss formula

Loss kWh per cycle ≈ capacity × (1 ÷ efficiency − 1). Annual loss = loss per cycle × cycles/year. kg CO₂ = annual loss kWh × (gCO₂/kWh ÷ 1000). Renewable charging assumes ~0 marginal gCO₂ on those loss kWh.

Make storage greener

Charge from on-site solar surplus, community solar, or documented renewable tariffs during low-carbon grid hours. Pair with Solar Daily Yield and Carbon Offset tools for full-site context.

Frequently asked questions

Q: Include manufacturing emissions? A: This is operational loss only—embodied carbon is separate LCA. Q: Partial cycles? A: Enter equivalent full cycles per year (annual throughput ÷ capacity). Q: 95% efficiency? A: Loss shrinks—but never zero.