Want to know more about how we’ve calculated Meridian Energy’s power production?

**FOR WIND**

To determine yesterday’s total energy potential from wind, we’ve calculated the amount of power produced by Meridian’s West Wind and Te Uku wind farms, using the observed hourly windspeeds at these locations throughout the previous day. The hourly windspeeds are used to calculate the amount of energy each wind farm is able to produce at those speeds.

The total wind energy displayed is the combined output for both sites. West Wind and Te Uku are two of Meridian’s largest producing wind farms. They also have three other wind farms - Mill Creek, Te Apiti and White Hill.

You can find out more about how Meridian’s wind energy is produced here.

**FOR HYDRO**

To calculate yesterday’s total energy potential for Meridian’s Lake Pūkaki and Lake Manapōuri hydro stations, we used the observed cumulative rainfall over the 24 hours of the previous day at a point at each hydro lake.

The total rainfall is multiplied by the amount of energy each hydro station is able to produce for a given amount of rainfall. ‘Rainfall’ is assumed to just fall over Lake Pūkaki or Lake Manapōuri, in fact, their catchment is much larger than their surface area. The inflows are assumed only via the rain that falls at the time, not natural river flows from the wider catchment.

We refer to this as “Yesterday’s Energy Potential from Rainfall” because rain that fell yesterday will not produce energy until the captured water is released through the turbines, which may be some time in the future.

You can find out more about how Meridian produce hydro energy here.

**WHAT IS A MEGAWATT HOUR?**

A** megawatt hour** (MWh) is a unit of energy. It equates to one million watts per hour, or 1000 kilowatts per hour. 1MWh is enough to power 50 New Zealand homes for a day.

**HOW DID WE PRODUCE OUR FACTOIDS?**

We’ve used the following assumptions to provide some interesting ways to visualise how much power this equates to in everyday life.

· A typical NZ household uses approximately 20kWh per day

· Boiling an electric kettle uses 0.1kWh and makes approximately six 250mL cups of tea.

· A ‘hot’ load of washing uses 4.5kWh