You currently have everything at priority 1, which would be bad if your power plant ever got damaged below 76% output. If you set up some module priorities, this warning should go away. You just want your essential systems at priority 1 (eg thrusters and FSD, so you can escape in emergencies with a damaged/underpowered power plant), and less important ones at lower values (like the cargo hatch and fuel scoop).
Setting priorities also allows you to shut down less important modules on your ship when deploying weapons which may otherwise use more power than your existing plant can provide. This isn't an issue on your current setup as you have surplus power, but may help with future builds or if you want to save money or weight with an undersized power plant.
This page should help explain:
http://elite-dangerous.wikia.com/wiki/Module_priority_control