In grid-connected systems the electricity produced by solar (PV) modules is used directly in the building and any excess energy is fed into the grid. When the solar electric system does not produce enough electricity for the building's needs, power is drawn from the grid. In a large building, such a solar electricity system can reduce the peak daytime power consumption from the grid, thus reducing electricity costs, when the demand for electricity exceeds supply then the system has to import electricity from the national grid. A net-metering arrangement ensures that the rate paid for exports to the grid is the same as that for electricity bought from the grid. Also, the solar PV panels can replace standard roof materials, effectively reducing the investment needed in the solar electricity system. Alternatively, there are solar roof tiles which can create entire roofs looking like traditional tiled roofs.

When the system is in place it begins to pay for itself right away by producing electricity. (Most houses use 4-5000 Kwh of electricity per year and this can be replaced with a 4-5 Kwp PV system).
As the electricity is generated where it is consumed, transmission and distribution losses are avoided, this is the micro-generation of each building's power and heating requirements. On its own solar PV can make a significant contribution to electrical energy demand depending on the size of system, but not to heating.

Solar electricity is particularly advantageous in situations where the power is used for applications such as cooling and air conditioning, with peak loads during the day-time when the solar electricity production is at its highest level. [This is relevant where there are large industrial or commercial PV arrays. Virtually all domestic housing in the UK does not need solar for cooling, but would make more efficient use of solar energy for heating water.