Speaking on the power devices builtin statistics reporting capabilities level, not all devices support providing statistics ... Use the upower command of UPower to list power devices with the option -e like so(this is a demonstration on a test system):

$ upower -e
/org/freedesktop/UPower/devices/line_power_ADP0
/org/freedesktop/UPower/devices/battery_BAT0
/org/freedesktop/UPower/devices/DisplayDevice

Then check the information of the device you want with the option -i ... Names are pretty descriptive, so the direct power line:

$ upower -i /org/freedesktop/UPower/devices/line_power_ADP0
  native-path:          ADP0
  power supply:         yes
  updated:              Fri 11 Aug 2023 03:45:32 PM +03 (68 seconds ago)
  has history:          no
  has statistics:       no
  line-power
    warning-level:       none
    online:              yes
    icon-name:          'ac-adapter-symbolic'

and as you can see, it doesn't have statistics ... So, information about current power consumption (among other information) can't be pulled from that device.

While the battery:

$ upower -i /org/freedesktop/UPower/devices/battery_BAT0
  native-path:          BAT0
  vendor:               LGC
  model:                L16L2PB2
  serial:               5545
  power supply:         yes
  updated:              Fri 11 Aug 2023 03:47:33 PM +03 (2 seconds ago)
  has history:          yes
  has statistics:       yes
  battery
    present:             yes
    rechargeable:        yes
    state:               charging
    warning-level:       none
    energy:              5.06 Wh
    energy-empty:        0 Wh
    energy-full:         17.99 Wh
    energy-full-design:  30 Wh
    energy-rate:         9.238 W
    voltage:             7.744 V
    charge-cycles:       N/A
    time to full:        1.4 hours
    percentage:          28%
    capacity:            59.9667%
    technology:          lithium-polymer
    icon-name:          'battery-low-charging-symbolic'
  History (charge):
    1691758053  28.000  charging
  History (rate):
    1691758053  9.238   charging

does have statistics and among those is energy-rate: which you can isolate and format for printing with something like this:

$ upower --show-info /org/freedesktop/UPower/devices/battery_BAT0 |
awk '/energy-rate:/{print $2}'
10.828 # <--- output

However, the statistics update interval might vary and updated: shows the time the statistics were last updated, but you can force statistics refresh of a certain device with for example:

busctl call org.freedesktop.UPower \
/org/freedesktop/UPower/devices/battery_BAT0 \
org.freedesktop.UPower.Device Refresh

and you can pull for e.g. energy-rate every for example three seconds with something like this:

while sleep 3
do
# Refresh device statistics
busctl call org.freedesktop.UPower \
/org/freedesktop/UPower/devices/battery_BAT0 \
org.freedesktop.UPower.Device Refresh
# Query the device statistics
upower -i /org/freedesktop/UPower/devices/battery_BAT0 |
awk '/energy-rate:/{print $2}'
done