kWh is energy used over time; kW is the rate of use at an instant. Enter one plus a time period to get the other.
kW tells you the size of load at one moment (like a panel rating); kWh tells you total energy consumed or produced over the period.
A 5 kW solar array is a power rating — what it can output at peak sun. Over a day it might produce 20 kWh of energy — what actually gets used or sold back. Utilities bill you in kWh (energy), while equipment like inverters and panels is rated in kW (power) — this converts cleanly between the two once you know the time period involved.
This distinction trips people up constantly in solar conversations — a salesperson quoting "an 8kW system" is describing peak power capacity, not the energy it will actually deliver over a day, week, or month. Converting between the two, using the actual hours involved, is the only way to get from an equipment spec to a number you can compare against your utility bill.
kWh — you're billed for total energy consumed over the billing period, not the peak power your house happened to draw at any moment.
The panel's kW rating is its maximum instantaneous output under ideal sun; multiply that by actual sun-hours in a day to estimate the kWh it will actually produce, as our production calculator does.
You can, but only if the device runs at that exact power level for the full 24 hours — most loads (and all solar arrays) vary throughout the day, so using actual average hours of operation, not a flat 24, gives a realistic result.