Who this is for
Manufacturers and plant owners in South Africa weighing solar as an answer to load shedding and rising tariffs — who want to know honestly what solar can and cannot run on a factory floor, before committing capital. This pairs with our guide on protecting a line from load shedding.
The question behind the question
"Can solar run my line?" is really three questions: which of my loads can solar run, for how many hours, and at what cost versus grid and diesel. Solar is not a like-for-like grid replacement you bolt on — it is a power source with a daily and weather-dependent profile that has to be matched to what your line actually draws, when.
Decision rule: start from your load profile, not the roof area or the panel price. The right system is sized to what your line draws, hour by hour — and the answer for thermal-heavy plants is very different from electrical-load plants.
The load profile decides everything
Solar suits some loads beautifully and others badly. The split:
Loads that suit solar
- Motors and drives — conveyors, pumps, fans, mixers, packaging machines. Steady, daytime, predictable.
- Compressed air — a major, constant electrical load on most lines; a strong solar candidate.
- Lighting, HVAC, offices, controls — easy daytime loads.
- Light processing — most plastics, packaging, fabrication, and assembly electrical loads.
Loads that fight solar
- Large thermal loads — electric ovens, furnaces, boilers, dryers, electric heating. These draw enormous power; sizing solar to cover them is often uneconomic. Gas or grid usually wins.
- High-inrush / peaky loads — large motors starting, induction heating; need careful inverter and battery sizing.
- 24-hour operation — night shifts need battery or another source; solar alone can't.
This is why a plastics or packaging plant can often go heavily solar, while a foundry, bakery, or heavy food-processing plant with big thermal demand cannot run those loads on solar economically — though it can still solar-power its electrical balance.
The three system types
| System | What it does | Best for | Limitation |
|---|---|---|---|
| Grid-tied (no battery) | Offsets daytime grid use; cuts the bill | Cutting tariff cost where grid is reliable | Shuts off during load shedding — no backup |
| Grid-tied + battery (hybrid) | Daytime solar + battery ride-through + grid/genset backstop | Most factories — bill saving and load-shedding cover | Battery cost; sized to hours of cover needed |
| Off-grid / island-capable | Runs independently of grid | Sites with no/very poor grid | Largest battery and capex; usually needs genset for resilience |
For load-shedding South Africa, the hybrid (grid-tied + battery) is the usual sweet spot: it cuts the tariff bill on sunny days and keeps production through the cuts, with the grid or a generator as backstop for night and weather.
How to size it — the honest method
- Measure the load profile. Log the line's real kW draw over a representative week — by hour, by shift, by season. This is the single most important input, and where a visibility/metering layer pays off. See measuring a line without a new PLC.
- Separate electrical from thermal. Decide which loads go on solar and which stay on grid/gas/genset.
- Size PV to the daytime electrical load you want to cover, with realistic SA irradiance and seasonal derating.
- Size the battery to the hours of cover you need through cuts and into early evening — battery is the expensive part, so size it to need, not aspiration.
- Keep a backstop. Grid and/or a critical-load generator for night shifts, cloudy spells, and large thermal loads.
- Run the payback. Capital vs avoided grid tariff + avoided diesel + avoided downtime. This is a total-cost-of-ownership calculation.
Failure mode: sizing solar to roof area or to a round "we want to go green" number instead of to the measured load profile — then discovering the system can't carry the compressor at 7am or the line at all on a cloudy week. Measure first.
What it costs, 2026
Commercial-industrial solar-plus-battery is sized in kW/kWh, so cost spans a wide range:
- Smaller hybrid (covering a modest electrical load + a few hours battery): roughly ZAR 1.5–4 million.
- Mid-scale (a full electrical line load, meaningful battery): roughly ZAR 4–10 million.
- Large / island-capable: ZAR 10–15 million+.
Payback is typically 3–7 years against the combined cost of grid tariff and diesel — faster where tariffs are high and load shedding is frequent. The diesel you don't burn is often the biggest line in the payback.
The controls still need protecting
Solar and batteries change where your power comes from, but the switchover events (solar↔battery↔grid↔genset) are still transients. The controls UPS, safe-shutdown logic, and surge/undervoltage protection from our load-shedding protection guide still apply — a hybrid system that switches sources cleanly protects product and electronics through the transitions.
What CISH does
We don't sell panels — we engineer the line side: measuring the real load profile, separating solar-suitable from thermal loads, specifying how the line's controls and drives behave across source switchovers, and integrating solar/battery/genset with the production line so it runs clean. We then work with solar EPC partners on the generation side. See Line Upgrade & Digitalisation and Commissioning & Maintenance.
Frequently asked questions
Can solar really run a production line?
Much of one, during daylight, if the loads are mostly electrical and steady. Solar-plus-battery can also bridge load-shedding gaps. Large thermal loads and 24-hour operation usually still need grid, gas, or a generator in the mix.
How much does a factory solar system cost?
From around ZAR 1.5 million for a smaller hybrid to ZAR 15 million+ for large or island-capable systems, depending on the load covered and battery hours. Payback is usually 3–7 years against grid and diesel.
Which loads should stay off solar?
Large thermal loads — electric ovens, furnaces, boilers, dryers — are power-hungry and usually uneconomic to run on solar. Keep them on grid or gas and put solar on the electrical balance (motors, air, packaging, lighting).
Do I still need a generator with solar?
Usually yes, as a backstop for night shifts, cloudy days, and large or critical loads. The common pattern is solar-plus-battery for daytime production plus a generator for critical loads and extended outages — minimising diesel rather than eliminating it.
What's the first step?
Measure the line's real load profile by hour and shift. Every sizing and payback number depends on it, and it's the step most often skipped before a solar quote.