 Sporting. Lovely. It makes you strong and fit. You sweat out your laziness and you can lose your energy. And the power often is impressive. This is a typical Dutch couple in a typical Dutch dwelling. Everything is quiet and you would expect that they don't use any energy. But while these two are asleep the house still requires 200 watts of power. Power is the amount of energy one uses or produces during a certain period. Unit, joule per second. Or in other words, watt. 60 watts. You don't bring it after the whole night. It's a waste of energy. Okay, number two. Let's go. And come on boys, come on. Hey guys, I'll make a little bit. Number three, four and five. 300 watts each. Making coffee, 900 watts. If you keep the hot plate on the demand will remain 900 watts. Energy is power times the period of time that this power is delivered. Unit, joule, watt hour, or calorie. Leave your coffee machine on for 20 minutes and you will have used 300 watt hours. 400 watts. 250 watts. Toasting bread, 1 kilowatt. But it can even get worse. Do you see where we are? You don't need to be 19. 250 watts, 11. The energy required for heat is immense. When the heating is turned up the boiler switches on and then demands at least two and a half kilowatts. Number two to nine. On the place rust. Under that, number two on the slag. 30 meters. Showering is one of the most energy squandering activities at home. The tank of a boiler has a certain stock of hot water but this needs to be heated up and cold water is entering the tank. When a boiler switches on because someone is showering approximately 10 kilowatts of power is demanded. In other words, 10,000 watts. This means 30 rowers each delivering 333 watts. An insane amount of power for just a shower. Six minutes of showering has already used 1 kilowatt hour. 12 minutes, 2 kilowatt hours. Half an hour, 5 kilowatt hours. The shower is weird again. That's rough. Good luck for our rowers who for 8 hours only have to deliver the basic power of the house until the couple returns. Unfortunately, today the basic power is unnecessarily high because the thermostat has not been switched down but it can be done. In producing, an invisible world is hiding in the house and in the equipment we use. Everything we use at home costs energy. A Dutch household requires approximately 1,800 watts. Based on the power our rowers deliver 250 watts on average we would require 7 rowers permanently. But this is on average. The peaks in usage can sometimes go up to 20 kilowatts. That is almost impossible. Or is it? This is the same house but with improvements such as extra thermal insulation a heat pump and solar cells. In the open online course Zero Energy Design, TU Delft will teach you how to liberate all rowers from their slave labor. How? By making the house energy neutral.