A solar quote can make the panels sound like the main event. In practice, the electrical design determines whether a system is safe, compliant and useful for the way you live or work. This guide to solar PV electrics sets out the parts of a solar installation that deserve proper attention before work begins.
Solar can reduce the amount of electricity you buy from the grid, but the result depends on your roof, daytime consumption, existing electrical installation and plans for the property. A well-designed system should fit the building rather than force the building to fit the system.
A guide to solar PV electrics: the system behind the panels
Solar panels generate direct current (DC) electricity. That power travels through protected DC cabling to an inverter, which converts it into alternating current (AC) electricity for use by your property. The inverter then connects safely to the consumer unit or, in some designs, a dedicated distribution board.
When generation is greater than the property is using, surplus power may charge a battery if one is fitted, or be exported to the grid. When generation is lower, the property draws electricity from the grid as usual. Solar PV does not normally provide electricity during a power cut simply because the sun is out. Standard systems switch off to protect electricity network engineers working on the supply.
The key electrical components are the inverter, isolators, protective devices, generation meter where required, cabling, earthing arrangements and connection into the existing installation. Each must be selected and installed for the particular property. There is no sensible one-size-fits-all design.
Start with the existing electrical installation
Before specifying panel numbers or battery capacity, a competent electrician should understand the condition and capacity of the existing installation. An older consumer unit, limited earthing arrangement, damaged accessories or unresolved faults may need attention first.
The consumer unit must have space and suitable protection for the solar supply. Depending on the design, this can involve a dedicated circuit breaker, residual current device protection and clearly labelled isolation points. The arrangement must meet current wiring regulations and allow the system to be safely tested, maintained and isolated in future.
This is particularly relevant in older Plymouth properties, where consumer units and supply arrangements can vary significantly from one home to the next. A recently upgraded board may make the electrical connection straightforward. A property with an outdated fuse board may need an upgrade before solar is connected. That is not unnecessary extra work – it is about ensuring the new generation equipment is not attached to a weak point in the installation.
For commercial premises, the assessment should also consider three-phase supplies, existing demand, distribution boards, plant and operating hours. A business that uses electricity heavily through the day may benefit from a different system design than a household where demand rises mainly in the evening.
The inverter is more than a box on the wall
The inverter is the working centre of a solar PV system. It needs to be correctly sized for the array and installed in a location with appropriate ventilation, access and protection from avoidable heat or moisture. A loft may seem convenient, but high summer temperatures can affect performance and maintenance access can be poor. A garage, utility room or suitable external location may be more practical, depending on the property.
There are trade-offs in inverter sizing. A larger inverter can accommodate more panel capacity, while a smaller unit may be suitable for a modest roof area and lower expected output. The right answer depends on the array design, roof orientation, shading and electrical connection limits, not just the biggest figure on a quotation.
Roofs with different orientations or partial shade may need separate strings, optimisers or microinverters. These options can improve output in the right circumstances, but they also add cost and complexity. A proper survey should identify chimneys, trees, dormers and neighbouring buildings that could affect production across the year.
Solar batteries and backup power
A battery stores surplus solar electricity for later use. It can be useful where a household is out during the day but uses more energy in the evening, or where a business has predictable demand after solar generation falls. It may also charge from the grid at lower-cost times on a suitable tariff.
A battery does not automatically make a property independent from the grid, and it does not automatically provide backup during an outage. Backup requires a specifically designed arrangement, often with a separate essential-loads circuit or changeover equipment. The system needs to prevent any unsafe backfeed to the network.
Battery size should be based on actual consumption patterns, not simply a desire to store every possible unit generated. An oversized battery can take longer to justify financially, especially if much of its capacity is rarely used. Future plans matter too. An electric vehicle, heat pump or growing business may change the best size of solar and storage system.
Your grid connection and DNO approval
Connecting generation equipment to the public electricity network involves the local Distribution Network Operator, or DNO. Small domestic systems may fall under the G98 process, which is generally notified after installation. Larger or more complex systems can require G99 approval before they are connected.
The installer should establish the correct route and manage the required paperwork. This is not a formality to overlook. The DNO must know about generation connected to its network, and approval may affect system size, export capability or the equipment selected.
Where export is limited, the system may use an export limitation scheme to keep exported power within an agreed level. This can be appropriate where the local network has constraints, but it should be clearly explained. Ask what the system will do with surplus generation once the export limit is reached, particularly if no battery is included.
Certificates, testing and handover
The electrical work should be inspected and tested when complete. You should receive appropriate certification for the electrical installation, together with clear circuit labelling and operating information. In England, notifiable domestic electrical work also needs to be dealt with correctly under Building Regulations.
Where a system is intended to support an application for Smart Export Guarantee payments, the installation and paperwork must meet the relevant supplier and scheme requirements. Many suppliers require MCS certification, so check this before committing if export payments are part of your calculation.
A useful handover should cover how to isolate the system, how to read monitoring data, what normal operation looks like and who to contact if there is a fault. Keep certificates, commissioning records, warranties and DNO correspondence with the property documents. They can be valuable for future servicing, insurance queries or a house sale.
Questions worth asking before you accept a quote
A clear quotation should describe the electrical scope, not only the panel brand and predicted output. Ask whether the consumer unit has been assessed, where the inverter and isolators will be located, how cable routes will be finished and whether any remedial electrical work is excluded from the price.
You should also ask how the system deals with shading, whether the quoted battery provides backup power, what DNO process applies and which certificates you will receive. If an installer promises a precise saving without first understanding your electricity usage and tariff, treat that figure with care. Generation estimates are useful, but they are not a guarantee of savings.
Do not overlook workmanship details. Neat cable routes, suitable trunking where needed, secure external equipment and accurate labels make the installation safer and easier to maintain. These details are often where experienced electrical work shows.
Protect the investment with proper electrical support
Solar PV brings generating equipment, DC wiring and potentially battery storage into a property that may already have an EV charger, electric heating or substantial commercial loads. Changes should be considered together. Adding an EV charger after solar, for example, may create an opportunity for smart charging and better use of surplus generation, but the supply and load management still need checking.
Periodic inspection and prompt fault investigation help keep the installation dependable. Warning lights, repeated inverter shutdowns, damaged external isolators or unexplained changes in output should not be ignored. The issue may be with the solar equipment, but it could also relate to the wider electrical installation.
For property owners across Plymouth, a solar project is most successful when the roof work and electrical work are planned as one job. Goodwin Electrical can provide practical advice on the electrical condition of your property, consumer unit capacity and the safe integration of solar-related equipment. Start with a proper assessment, ask for clear answers, and choose a design that will still make sense as your energy use changes.