kW vs kWh: The Distinction That Matters
kW is power, kWh is energy. Understanding the difference is essential to specifying inverters, batteries and tariffs correctly.
Power Versus Energy
kW is power: how much electricity a system can deliver at once. kWh is energy: how much electricity it can store or deliver over time.
Example: a 100 kW / 400 kWh battery energy storage system can theoretically deliver 100 kW for approximately 4 hours under simplified conditions.
Why It Matters for Storage
Battery specifications include state of charge (SOC), depth of discharge (DoD), round-trip efficiency, cycle life and C-rate. Sizing a battery means sizing two different things at once: the power rating for how fast energy moves, and the energy rating for how much of it there is.
Why It Matters for Solar
A solar array is rated in kWp (kilowatt-peak): the power it produces under standard test conditions. What a customer actually consumes is kWh. Matching the two is what system sizing is about: energy demand, peak power, solar resource, battery requirements, autonomy and system losses.
Why It Matters for Tariffs
Electricity is metered in kWh. Understanding kWh is understanding the bill; understanding kW is understanding the demand charge and the equipment rating. Both numbers appear in every serious energy proposal.
