Glossary
Quick definitions used across WattNeeds guides. Niche: camping / home backup / van-life only.
Watt (W)
Rate of power use right now. A 60 W light draws 60 joules per second.
Watt-hour (Wh)
Energy = watts × hours. A 60 W light for 5 hours uses 300 Wh. Power stations are sold by nameplate Wh.
Nameplate Wh vs usable Wh
Nameplate is the rated pack energy. Usable energy is lower after BMS reserves (DoD) and conversion losses.
Depth of discharge (DoD)
Fraction of the pack you plan to use. WattNeeds default 0.90 for LiFePO₄ planning.
Inverter efficiency (η)
AC conversion efficiency. Default 0.90; use ~0.85 if mostly uncertain AC loads; higher if mostly DC/USB.
Buffer / headroom
Extra planning margin (default 15%) for imperfect estimates and real-world variance.
Surge / continuous watts
Inverter limits: continuous = steady load; surge = short startup spikes (compressors, motors). Capacity (Wh) ≠ ability to start a load.
Autonomy
Days you need to run without a reliable recharge (mains, solar, vehicle).