A great option if the site suits, with a 300l storage tank very generous for just two. We managed a family of 5 with a similar sized solar HW system. The electric booster was connected to off peak (night rate). It was easy to monitor how well the solar HW performed. We usually left the power to the booster element turned off. It was only during prolonged periods of heavy cloud and wet that the booster was needed.
Depending on where you are flat plate HW collector which is cheaper than evacuated tubes may be adequate.
