I have a hot-water jug that keeps water hot (say, at about 70 C). To compute its operation cost, I would like to comput its daily energy consumption. The label on the jug says "800 Watt", but this is probably the maximum power used when it is actively heating the water. I would like to know how much energy is spent, on average, to keep the water hot? Some more details:

• The room temperature is about 20 C.
• The jug is made of steel plates with air between them (maybe there is another insulating material between the plates - I could not find out exactly).
• The jug capacity is about 5 litre, but usually it contains about 2 litre water.

Based on this information, is it possible to approximate how much Watt*hour it consumes per day?

I have a hot-water jug that keeps water hot (say, at about $70\, ^{\circ} C$). To compute its operation cost, I would like to compute its daily energy consumption. The label on the jug says "800 Watts", but this is probably the maximum power used when it is actively heating the water. I would like to know how much energy is spent, on average, to keep the water hot. Some more details:

• The room temperature is about $20\, ^{\circ}C$.
• The jug is made of steel plates with air between them (maybe there is another insulating material between the plates—I could not find out exactly).
• The jug capacity is about 5 litres, but usually it contains about 2 litres of water.

Based on this information, is it possible to approximate how much Watt*hour it consumes per day?