Turning on the hose to water the lawn will allow huge amounts of water onto a relatively narrow area of the lawn per running hour of the hose. Many people forget and leave the house running for hours, but a much more efficient way is to install an irrigation system.
Efficiently unleash automatic irrigation systems to free you from the task and efficiently water your gardens for you.
If the cold tap in you kitchen sink runs at 18-20 litres/min then your lawn will be receiving a similar amount via the hose 1000 litres/hr. But infact most lawns benefit best from regular small amounts of water every couple of days. Since sprays only work for short periods (10mins) regularly. You could spread that 1000 litres per hour over a large area of your lawn very efficiently with an automated pop up lawn watering system and use no greater quantity.