Solar Energy Solutions
Grid-tied solar PV
A grid-tied solar PV system generates electricity on your own roof or land and uses it first, with the grid still connected in the background. For most businesses and farms it is the most direct way to reduce what you buy from Eskom or the municipality, without giving up the reliability of a grid connection. This page explains how it works, how it differs from hybrid and off-grid systems, and what it takes to connect one legally in South Africa.
- Connection
- Runs in parallel with the Eskom or municipal supply
- How it saves
- Solar is used on site first; the grid tops up the rest
- Compliance
- SSEG approval, NRS 097-2-1 and SANS 10142-1
- Design life
- Engineered to perform for 25+ years
How a grid-tied system works
PV modules, the solar panels, convert sunlight into direct current (DC) electricity. Modules are wired in series into strings, so that their voltages add up to the range the inverter is designed for. On larger systems several strings are brought together in a PV distribution board, or combiner box, fitted with fuses, isolators and surge protection.
The inverter converts that DC into alternating current (AC) at the grid's voltage and frequency, and feeds it into your distribution board. From there it supplies whatever is running on site: lighting, air conditioning, compressors, cold rooms, production lines, and pumping, milking and packing loads. Larger sites use several inverters, sized together with the array.
Your site stays connected to the grid at the point of connection, the boundary between your installation and the utility's network, usually at the main meter. Whenever solar production is lower than demand, at night, in poor weather or when a large load starts, the grid supplies the difference automatically. Nothing needs to switch over and nothing on site notices the change.
Metering records what flows in each direction. Where export is permitted, the distributor installs or approves a bidirectional meter that measures energy imported from the grid and energy exported to it separately.
Self-consumption, export and export limiting
Self-consumption is the share of your solar production that is used on site as it is generated. It is where most of the value of a grid-tied system lies, because every kWh you produce and use yourself is a kWh you do not buy. Designing for high self-consumption starts with your load profile: how much power the site draws, hour by hour, across a working week and through the seasons.
When production exceeds demand, at midday on a weekend for example, the surplus would naturally flow out to the grid. Whether that is allowed, and whether you are credited for it, depends on your distributor. Many systems are therefore designed as zero-export or export-limited: a meter at the point of connection tells the inverters how much the site is using, and they reduce production so that nothing, or no more than an agreed limit, leaves the property.
Zero export is a design choice, not a shortcoming. A well-sized array on a site with steady daytime demand loses very little production to this limiting, and it keeps the connection application simpler.
What happens during grid interruptions and load-shedding
A standard grid-tied inverter switches off when the grid goes down. This is anti-islanding protection, and NRS 097-2-1, the specification for connecting embedded generation to the utility network, requires it. It stops your system from energising a line that technicians working on the network believe is dead. It is a safety function and it cannot be bypassed.
The result is that a grid-tied system on its own does not keep a site running during grid interruptions and load-shedding, even on a clear day. If backup matters to your operation, the answer is a hybrid inverter with battery storage, or a battery inverter added alongside the existing system. When the grid fails, a hybrid system disconnects the site from the network and keeps supplying the loads it was designed for from solar and battery, then reconnects when the grid returns.
Many businesses start grid-tied for savings and add storage later. Planning the electrical layout for that from the first day, with a separate essential-loads board and space for the equipment, keeps the later step straightforward.
Off-grid and hybrid systems
An off-grid system has no connection to the utility network at all. Solar, batteries and usually a standby generator carry the whole load, every hour of every day. The battery bank is sized for autonomy, meaning the number of days the site can run through overcast weather with little solar input, and the generator covers extended poor weather or demand beyond what the system was designed for.
Because an off-grid system has to cover the worst weeks of the year rather than an average day, it needs considerably more PV and storage for every kWh used, and it costs more as a result. It makes sense where a grid connection is unavailable, unreliable for long periods or impractical to extend: remote farm operations, lodges, telecommunications and monitoring sites, and buildings far from a supply point.
A hybrid system sits between the two. It stays connected to the grid like a grid-tied system, but adds batteries and an inverter able to run the site, or its essential loads, through an outage. It is the most common choice for commercial and agricultural clients who want both lower electricity costs and continuity.
Grid-tied, hybrid and off-grid compared
The same solar array can sit in any of these three arrangements. What differs is the grid connection, the storage and what happens when the supply fails.
| Aspect | Grid-tied | Hybrid | Off-grid |
|---|---|---|---|
| Grid connection | Yes, runs in parallel | Yes, runs in parallel | None |
| Batteries | None | Sized for backup and shifting solar energy | Sized for days of autonomy |
| Backup during outages | No, shuts down for safety | Yes, for the loads it is designed to carry | The system is the supply |
| Generator | Not needed | Optional, for long outages | Usually required |
| Relative cost | Lowest | Moderate | Highest for each kWh used |
| Typical use | Sites with a dependable grid supply and strong daytime demand | Businesses and farms that need savings and continuity | Remote sites with no practical grid connection |
Rooftop, ground-mount and carport structures
The mounting structure carries the array for its whole life, so it is engineered for the site's wind loading, roof or soil conditions and corrosion environment.
Rooftop
The most common choice for commercial, retail and education buildings. We assess the roof sheeting, purlins and trusses for the added load, plan safe access and walkways, and fix the array without compromising the roof.
Ground-mount
Suited to farms and industrial sites with open land. Fixed-tilt frames on driven or concrete foundations allow the best orientation and easy access for maintenance, with fencing and longer cable runs to plan for.
Carport and canopy
Structures over parking areas and walkways that generate power while providing shade. A good fit for shopping centres, business parks and schools where roof space is limited.
Connecting legally: SSEG approval and standards
In South Africa a grid-connected solar system is a small-scale embedded generator (SSEG). It needs the distributor's approval before it is connected, whether or not it exports. We handle the application as part of the project.
Approvals
- An application to the distributor, Eskom or the municipality, with the single-line diagram, inverter details and system size.
- Grid-connected systems up to 1 MW (1 000 kW) follow the normal application to the distributor. Systems above 1 MW also register with NERSA, the National Energy Regulator of South Africa.
- Registration depends on the grid connection and the system size, not on whether you export. Systems with no grid connection are exempt.
- A Certificate of Compliance (CoC) for the installation, issued by a registered electrical contractor.
Standards the design follows
- NRS 097-2-1: the utility interface, including inverter protection settings and anti-islanding.
- NRS 097-2-3: the simplified connection criteria distributors use to assess low-voltage connections.
- SANS 10142-1: the national wiring code for premises, including its requirements for embedded generation and PV installations, which SABS continues to update.
- Inverters with NRS 097-2-1 test certification, which most distributors require before they approve a connection.
Net metering and feed-in
- Some municipalities and Eskom credit exported energy on approved tariffs; others do not allow export at all.
- Credits, conditions and meter requirements vary by distributor and change over time, so we confirm the position for your supply point rather than assume it.
- We design the system to make sense on self-consumption alone, so export credit is a bonus and never the business case.
Questions about grid-tied solar
Will a grid-tied system keep my business running during load-shedding?
Not on its own. Standard grid-tied inverters shut down when the grid fails, by design, to protect people working on the network. To keep running through grid interruptions and load-shedding you need battery storage with a hybrid or battery inverter, which can be added to most grid-tied systems later if the original layout allows for it.
Do I have to register a system that does not export?
Yes. Registration depends on whether the system is connected to the grid and on its size, not on whether it exports. A zero-export system still needs the distributor's approval, and NERSA registration as well if it is larger than 1 MW.
Can I sell my surplus electricity back to the grid?
It depends on your distributor. Some municipalities and Eskom offer export credits on specific tariffs with a bidirectional meter; others do not. We confirm the position for your supply point and never build a business case that depends on it.
How big should my system be?
That comes from your load profile, not a rule of thumb. We study your consumption data and electricity bills, look at when the site uses power, and size the array and inverters for high self-consumption with little production lost to export limiting.
Is off-grid better value in the long run?
Rarely, where a dependable grid connection exists. An off-grid system must be sized for the worst weather of the year and usually needs a generator, so it costs more for each kWh used. For most connected sites a hybrid system gives the independence people are looking for at a lower overall cost.
How long does a grid-tied system last?
Our systems are engineered to perform for more than 25 years. PV modules usually carry long performance warranties from the manufacturer. Inverters are the component most likely to need replacement during the system's life, and we plan for that from the start.
See what grid-tied solar can do for your site
Share a recent electricity bill or your load-profile data. We will show you how much of your demand solar can carry, whether storage earns its place, and what the approvals involve. Every system is designed around your usage.
Power On!