Reactor.lua

local component = require("component")
local sides = require("sides")

local Reactor = component.energy_device
local Redstone = component.redstone
local MaxStorage = Reactor.getMaxEnergyStored()
local Running = false

while true do
  local stored = Reactor.getEnergyStored()
  local perc = (stored / MaxStorage) * 100
  if perc < 20 then
    Running = true
    Redstone.setOutput(sides.down, 15)
  elseif perc > 80 then
    Running = false
    Redstone.setOutput(sides.down, 0)
  end
  print(perc)
  os.sleep(5)
end