Below is a table that gives a rough indication of the specifications and energy that could be expected from a solar water heating system involving some 2 m2 of absorber area of the collector, demonstrating two evacuated tube and three flat plate solar water heating systems. Certification information or figures calculated from those data are used. The bottom two rows give estimates for daily energy production (kWh/day) for a tropical and a temperate scenario. These estimates are for heating water to 50 °C above ambient temperature.