Hey everyone! I'm getting into setting up autonomous solar systems and need some help figuring out electricity use for my four electric resistance water heaters. Each heater has a capacity of 3000W and holds 130 liters. I'm trying to understand how often these heaters will turn on daily, especially since my setup is remote, making it tricky to measure directly. Any tips on estimating this would be super helpful. Thanks in advance!
2 Answers
For your heaters, standby losses typically range from 1.2kWh to 1.8kWh per tank daily. It takes about 6kWh to reheat a full 130L tank after usage. Keep in mind that when heating, you may draw more than 130L as the system can heat replacement water. So, if you use water at night, the heater could be firing up several times by morning depending on your usage. Don't forget to consider these aspects when calculating daily consumption!
Water heaters often have a thermal switch that activates when the water temperature drops. For each boiler, you lose about 1 kWh/day through insulation. If the temp drops by 5°C, you'll need around 0.715 kWh to heat 130L back up. So the frequency of heating could be every 12 hours based on insulation losses. If you draw hot water for a bath, all four tanks might need a whopping 37.18 kWh to refill. This will require a substantial solar array! Consider if you’ll need power for other things like lights and tools too!
Got it! So if I understand correctly, the heating might really depend on how much water we utilize each day?