The UK government calculates that the electricity generated by a 4kW installation costs £310/MWh (total levelised). That’s about three times that of conventional hydro power or onshore wind farms.
Apart from all that, all forms of renewable electricity generation are a headache for the grid controllers, charged with maintaining an adequate electricity supply at the right frequency. They have no control over these scattered generating inputs and so have to ask thermal stations (except nuclear) to come on and offline to balance the load on the network. That makes these thermal stations inefficient, and likely unprofitable. While the output from wind farms is wind-dependent, PV is sun-dependent and so is useless at night. Until efficient means are found to store electricity at a reasonable cost, all renewables will suffer these defects.