The short answer is that a kilo-Watt represents Power, while a Kilo-Watt-Hour represents Power transmitted over a period of time, otherwise known as Energy. Most of us think of these terms as synonymous, but they are not. A KW is a measured real-time rate of electricity generated or consumed. A kWh is a measured amount of power generated, or consumed, over a period of time. If you have a solar generator supplying 6kW to a load …and you run that load for one-and-a-half hours, it will have consumed 9kWh of energy. The load required 6kW of power to run. It used 9kWh of energy over 1.5 hours. The (k) in front of either just means “one thousand,” so 1kW = 1,000 Watts.
To determine recharge time from the solar panels, just divide the utilized battery capacity (in kWh) by the daily solar harvest (in kWh/day). For instance, the MS-225 has a battery capacity of 25kWh and solar array has a daily harvest of 9kWh/day. Let’s assume you drain the battery down 80% (meaning 20% is left in the battery). The math: 25kWh x 0.80 = 20kWh. And 20kWh / 9kWh/day = 2.2 days of solar charge to bring the battery back up to a 100% State of Charge (SOC).