One of my favourite films is Back to the Future, in which (for the very few that haven’t seen it) Marty McFly is accidentally sent back in time, has to make sure his parents meet to save his existence, all while trying to find a way to get home. Famously in the film, Doc Brown tells Marty that the energy required to power the DeLorean time machine is “1.21 Gigawatts”, but how much power is that?
What is a Watt?
Firstly, let’s look at what on earth a watt is. A watt is a unit of power, which is equal to the amount of energy transferred every second. Giga means billion, therefore 1.21 Gigawatts is equal to 1.21 billion joules of energy transferred every second.
So, what can you do with 1.21 Gigawatts?
Let’s start off by saying 1.21 Gigawatts is a lot of power. A lot. Let’s take a look at what that is equivalent to.
1.6 million Horsepower
Horsepower is, as the name suggests, the power of 1 horse, which is equal to 745.7W, so 1.21 GW is equal to the power of 1.6 million horses. As you probably know, horsepower is normally used for cars and the current most powerful road car is the Bugatti Chiron at 1479BHP. This means that the power required to 1 DeLorean time machine is equal to the power of 1097 Bugatti Chirons, or 386342 Peel P50s.
2420 wind turbines
Currently, wind turbines operate at a maximum capacity of around 2MW, but they won’t produce 2MW of power all of the time. In reality, they operate, on average, at about 25% of the full capacity meaning they are only producing 0.5MW, meaning that you would need 2420 wind turbines to power one DeLorean time machine.
2.42% of the UK’s power demand
Throughout the year, the peak power demand of the UK is roughly 50GW and at it’s minimum it can get as low as 25GW. That means that the power required to send you back in time is enough to provide 2.42-4.84% of the UK’s power needs.
80.7 million energy-saving light bulbs
If we look at a 15W energy saving lightbulb, we would be able to power 80.7 million of these bulbs at full capacity for 1.21 GW.
So how long would it take to charge my phone?
Most likely, if you provided 1.21GW of power to your brand new iPhone X, it will probably blow up, but let’s just pretend it won’t. An iPhone X has a battery capacity of 10.35Wh, a watt-hour (Wh) is the amount of energy provided by 1 watt if run for 1 hour. This means that an iPhone X battery can produce 10.35 * 60 * 60 = 37260 joules of energy. The amount of time required to transfer 37260 joules of energy at a power of 1.21 GW of is 37260 / 1.21 billion = 0.000031s. So by the time you let go of the charger, your phone could’ve been charged multiple times.
Also with that amount of power you can charge…
A Tesla 75D in 0.27s.
The Worlds largest battery in 6.4 minutes.
An Alkaline AA battery in 0.000012s.
Finally, how is the car powered in the film? With a nuclear reactor, which probably still won’t be enough considering the smallest nuclear power plant in the USA only produces 582MW, and I doubt that fits inside a car. As for lightening, there is more than enough there at around 1 trillion watts. So if you want to go back in time, you better be prepared to carry around a medium-sized nuclear reactor or be ready to get struck by lightning, otherwise, you’re going to have to stay right where you are.