It's a common misunderstanding, but the term 'solar panel' is used for TWO completely different types of technology, with distinct applications -
THERMAL solar panels use the sun's HEAT - a simple, time-proven technology, whereby the sun's warmth heats water flowing through tubes inside the panels, which accumulates in a tank to provide hot water for domestic purposes - usually for kitchen/bathroom use but can also be applied to radiator or underfloor heating systems. A typical family home needs a 300-litre water tank heated by 2 solar panels (about 4m²). Alternatively, to heat a pool, a rough guide is that the number of panels needed is equivalent to half the pool's surface area.
PHOTOVOLTAIC (PV) solar panels use the sun's LIGHT and are made up of photo-sensitive cells which convert sunlight into electricity. This technology has progressed rapidly in recent years, but a considerable number of PV panels (around 30m²) are still needed to fulfil the normal electrical requirements of a typical family home.