Watt is a unit of Power and we know that Power is simply the ratio of Energy over time. Therefore:
Power = Energy / time
Energy = Power * time
where time is in seconds therefore convert 24 hour to seconds:
time = 24 hours * (3600 seconds / hour) = 86,400 s
Energy = 60 Watt * 86,400 s
Energy = 5,184,000 Joules
