Pedantic note: It’s not “.7kW per hour”. Watts is a measure of power, it’s already Joules/second. You just want “.7kW”. For 6 hours, you still won’t get 4kW

Pedantic note: It’s not “.7kW per hour”. Watts is a measure of power, it’s already Joules/second. You just want “.7kW”. For 6 hours, you still won’t get 4kWh, because you need to adjust for less than ideal angle, and less than full sun days. But if you got 3kWh on a good day, that’s still 10-12 miles of additional range.