This is the most common question about the residential unit. The answer is not a single figure, because the question carries two separate questions inside it: how much energy does it take to bring the water to the temperature you want, and how much does it take to hold it there all day?

Looking at the two separately is the soundest way to understand daily use. The example below is the same one shown on the residential page.

Conditions in this example

GXF 7-T, 7 kW. The liquid heated is 100 litres of water. The temperature goes from 20 °C to 45 °C, a rise of 25 °C.

Step 1: taking the water to 45 °C

This stage takes 25 minutes and uses 2.9 kW of electricity. One point to note: this figure covers only the run from the starting point to the target. It is a one-time cost.

Step 2: holding the water at 45 °C

This is where the daily use actually sits. How long the unit runs depends on how fast the water cools down — that is, on the insulation of the home. Electricity used over 24 hours, by hourly temperature drop:

• Good insulation (5 °C drop per hour) — 13.95 kW.
• Average insulation (7.5 °C drop per hour) — 20.93 kW.
• Poor insulation (10 °C drop per hour) — 27.91 kW.

To see your own figures

The example above is based on 100 litres of water. If your volume, starting temperature or target temperature are different, you can enter your own values in the calculator at the bottom of the residential page: it shows the time, the energy used and the 24-hour figure together.

The holding figures are averages; they vary with the size of the home, its insulation and the climate.