Possible reasons are:
1. The collector area of the solar water heater is insufficient and cannot absorb enough solar heat.
2. The collector of the solar water heater is poorly oriented and is not fully exposed to the sun.
3. The water tank of the solar water heater is poorly insulated, leading to heat loss.
4. There is too much scale or dirt inside the water tank of the solar water heater, which affects heat transfer.
5. The solar water heater pipes are leaking, causing heat loss.
Solution:
1. Increase the surface area of the collector or replace it with a more efficient collector.
2. Adjust the direction of the collector to ensure full exposure to sunlight.
3. Check the insulation condition of the water tank and replace it in time if there is a problem.
4. Clean the inside of the water tank regularly to avoid tarbe or excessive dirt.
5. Check whether the pipeline is leaking and repair it in time if there is a problem.