You cannot directly equate photons with Watts there is a time element involved, Photons are carriers of energy measured in Joules while Watts are units in which the rate of flow of energy is measured i.e 1 Watt = 1 Joule per second.

You must talk of Photons per second or energy accumulated in units such as KWh (3,600,000 Joules)

If you are interested in solar panels The figures are that Solar Photons are assumed to carry 1.1 Ev which converts to 1.76 * 10^-19 Joules while the typical efficiency of a solar panel would be 15% while the incident energy in sunlight at ground level is quoted as 1KW per meter^2.