Solar Electrical Power Basics

A solar power system consists of several electrical components that must be sized and configured correctly to generate electricity. These include photovoltaic panels, a solar inverter, DC isolators, cable and potentially a battery energy storage system to store captured energy for night-time and/or Off-The-Grid usage. Within areas that suffer from mains power disruptions the installation may also include a standby power generator for long mains failures and even an uninterruptible power supply for critical IT systems.

Solar electricity systems are given a rating in kWp (kilowatts peak), which is a measure of the rate at which it generates energy at peak performance: at midday on a sunny day, for example. The total amount of electricity a solar PV system generates in a year is measured in kWh (kilowatt hours), which will depend on the system’s size (kWp), orientation, shading and how sunny its location is.

A typical domestic PV installation will be 1.5 to 3kWp. Each kWp will probably generate around 800 to 850kWh per annum (if ideally placed and not shaded). Perfect placement is generally accepted as south facing with a tilt of around 30-50degree. Solar PV panels are usually connected together to form what is termed an array. A typical solar roof array will generate 1200 to 2400kWh per annum (depending on how large it is). An average domestic home uses 4000kWh of electricity per annum on lights and appliances so it is likely that top up energy will be needed and this can be in the form of connection to the mains electricity supply or via a backup generator.

Connecting to the grid is not as complicated as it might seem. Most installers should start by informing the electricity District Network Operator (DNO). In England, Wales, Scotland and Northern Ireland, most solar installations do not require planning permission provided they respect certain criteria (your installer should offer guidance on this). Feed-In-Tariffs (FITs) enable consumers to get paid for the electricity they generate from their solar PV system and it guarantees a minimum payment for all electricity generated, alongside an additional payment for electricity exported to the grid. This is in addition to savings made on energy bills from using the solar electricity generated onsite.

Currently, energy consumers with PV installations get paid for exporting 50% of the electricity they generate from their system regardless of how much of that they end up exporting to the grid. Both the system and the renewable power system installer must be registered under the Microgeneration Certification Scheme.