It all comes down to efficiency, and between solar PV and solar thermal systems, the latter is generally considered more efficient. This is because solar thermal collectors are explicitly designed to capture heat from sunlight, achieving up to 70% efficiency. The captured heat directly heats the water in the storage tank, minimising energy loss during the conversion. It is also cheaper to install compared to a solar PV system with battery storage for hot water.
The downside of solar thermal systems is they only heat water. This means they are not suitable for generating electricity for other household needs. Their hot water storage capacity may also be a factor, especially when it’s cloudy.
On the other hand, solar PV with heat pump or electric heater are efficient in a way that they are multipurpose. Since solar panels generate electricity, they can be used for appliances besides hot water heating. They can also be expanded to create more electricity for the entire household.
Unfortunately, solar PV systems still require converting solar energy to electricity first, then using the electricity to heat water. This leads to some energy loss during the conversion stages. They also have a higher upfront cost.
Solar thermal is the best option for direct hot water heating with maximum efficiency and a lower upfront cost. If you want a multipurpose system for generating electricity for your entire home and hot water and are willing to invest more upfront, solar PV with battery storage and a heat pump can be an excellent choice.
The good news is that things are changing, with solar PV costs decreasing while battery storage technology is improving. Therefore, solar PV with heat pumps is becoming more competitive. Additionally, advancements in heat pump technology are making them even more efficient at heating water.
Energy Matters has been in the solar industry since 2005 and has helped over 40,000 Australian households achieve energy independence.
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