Based on a post by @tom_l
Energy and power are not the same thing
Energy, measured in kiloWatt-hours (kWh), is a measure of what it takes to do something (like cook a microwave meal). Power, measured in Watts (W), is the speed at which energy is being transferred. A 900W microwave cooks faster than a 700W one, even though the meal may be the same.
Power readings (in W) from your smart plugs need to be converted into energy readings (in kWh) before they can appear in the energy dashboard.
This can be done from the UI.
Feed your power sensors into this helper to get energy sensors:
Take care with the method. Nine times out of ten “left” is the best method rather than the default trapezoidal method.
Then for daily/monthly totals feed the energy sensors produced by the Riemann Sum helpers to utility meter helpers with daily/monthly cycles:
HA Energy Dashboard FAQ · GitHub.