The y axis under the hourly usage chart should be kW not kWh. If it's truly kWh it would be a cumulative value vs time with slopes varying with power
I was thinking the same thing, but looking again, it seems perhaps the problem is not so much the label on the y axis, as the fact that it should be a bar graph, with one bar for every hour, rather than a line graph. The line suggests that the kWh is defined continuously. As you point out, this wouldn't make sense. But the graph seems to have slope changes on an hourly basis. So perhaps the graph is indicating where the tops of the bars on an hourly bar graph would lie. If so, then kWh would make sense, indicating the total energy used during that hour.