[orra]

To put numbers on this, you can buy a C rated fridge freezer in the UK which uses 176 kWh of energy per annum.

That's an average power consumption of 20W. But electric heaters are say 1200W or 2000W.

[Avamander]

That includes the lights and all the rest. That gives you like 3m³ (790 gallons) of 60°C (140°F) water. Which is really not a lot.