ModulePowerLimitWarning.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace NeverBasicTweaks
{
    class PowerWarningTestModule : PartModule
    {
        [KSPField]
        public string engineModuleID;

        ModuleEngines engine;
        public double requiredPower;

        public override void OnStart(StartState state)
        {
            engine = part.FindModulesImplementing<ModuleEngines>().Find(m => m.engineID == engineModuleID);
                requiredPower = engine.propellants.Find(p => p.name == "ElectricCharge").currentRequirement;
        }

        void FixedUpdate()
        {
            vessel.GetConnectedResourceTotals(PartResourceLibrary.ElectricityHashcode, out double amount, out double maxamount);
            if (engine != null && amount < requiredPower)
            {
                ScreenMessages.PostScreenMessage($"You don't have enough electricity to run the engine! You have {amount}, but you need {requiredPower}");
            }
        }
    }
}