Commercial solar buyer's guide
Straight answers to the questions South African businesses ask before investing in solar, based on how Red Energy's My Solar Plan engine actually calculates a system. Every number on these pages comes from that engine, run on stated example inputs.
Worked examples
- Factory roof solar capacity1 548 panels (967.5 kWp) on a 5 000 m² roof, and what pitch and direction change.
- Warehouse solar savings70% of grid use replaced, about R764 000 a year excl. VAT, on a published City Power tariff.
- Commercial solar system sizing258 kWp solar only, or 294 kWp with a 150 kWh backup battery.
How much solar fits on my roof?
Red Energy's layout engine packs the actual panel it installs — a 625 W module of 2 382 × 1 134 mm — onto each usable roof face, with edge clearance, small gaps between panels and an access gap after every two or three rows. In the factory example, a clear low-pitch roof, that works out at about 194 W of panel capacity per square metre of building footprint. Skylights, plant, shading, fire-access routes and the roof structure reduce that on a real building. See the factory roof example.
Is my roof suitable?
- Direction. A pitched roof face pointing south (within 45° of due south) is never used: in South Africa it faces away from the sun. North-, east- and west-facing faces are used.
- Flat and low-pitch roofs. A face pitched at 10° or less is treated as flat and can be used whatever its direction.
- No suitable roof? My Solar Plan can also lay out a ground-mounted array on open land: rows of panels tilted 15° to the north, in blocks of two or three rows with 3.5 m between blocks.
- Condition and structure. Roof strength, sheeting condition, shading and roof fittings are confirmed at Red Energy's site inspection, not from imagery.
What size system does my business need?
Size to daytime electricity use, not to the roof. My Solar Plan divides your average daytime consumption by what one kilowatt-peak produces on an average day at your site, adds what a battery would need to recharge, and caps the result at what fits. Solar the business cannot use when it is generated is not counted as a saving, so a bigger system is not automatically a better one. See the system sizing example.
How much could my business save?
The indicative saving is the grid electricity solar replaces multiplied by the per-kWh rate you pay for it. In the warehouse example, a 151 kWp system replaces 70% of a 30 000 kWh-a-month site's grid use. Only per-kWh charges are valued: savings on demand, capacity and fixed charges are never claimed, and figures exclude VAT, tariff escalation, degradation, finance and tax. The model uses one average day across the year and does not yet deduct days a site is closed, so a business that shuts at weekends would save less than it shows. See the warehouse savings example.
What does it cost, and what is the payback?
A commercial system is priced from Red Energy's approved equipment configurations once a site inspection has confirmed the roof and the electrical supply. Simple payback is that price divided by the annual saving. My Solar Plan shows the saving first and leaves payback to the priced proposal, rather than publishing a generic rand-per-kWp figure that may not fit your site.
Batteries, backup and load shedding
A backup battery is sized from the power that must stay on and for how long. You can choose an operating level — Critical (25% of normal site load), Reduced (50%), Most (75%) or Full (100%) — or give a known backup load in kW, then the hours of autonomy you want. Installed capacity allows for a 90% usable depth of discharge and 95% discharge efficiency by default. On a time-of-use tariff a battery can instead be sized to cover Peak-period consumption. A standby generator can be included in the plan alongside solar.
Which electricity tariffs are covered?
Red Energy keeps a catalogue of verified 2026/27 business tariffs (commercial, industrial and agricultural), transcribed from each supplier's official, final tariff documents. When you continue with Red Energy, your actual tariff is selected from it. On the public plan you can enter your average monthly consumption and an average rate.
| Supplier | Tariff families |
|---|---|
| Eskom | Megaflex, Miniflex, Nightsave Urban, Businessrate, Nightsave Rural, Ruraflex, Landrate / Landrate Dx / Landlight |
| City of Ekurhuleni | Tariff A, Tariff B, Tariff C, Tariff D, Tariff E, Tariff J |
| City Power Johannesburg | Business Prepaid/Conventional, Three Part Tariff: LPU, Industrial Three Part TOU |
| City of Tshwane | Non-Domestic Single Phase: Conventional, Non-Domestic Single Phase: Prepaid, Non-Domestic Three Phase: Conventional, Non-Domestic Three Phase: Prepaid, Low-Voltage Three-Phase Demand Scale, Low-Voltage Three-Phase Demand Scale: Time of Use, 11kV Supply Scale, 11kV Supply Scale: Time of Use |
| Emfuleni Local Municipality | Commercial Prepaid, Commercial Conventional, Commercial SPU, Commercial LPU, TOU - Miniflex, TOU - Megaflex, TOU - Nightsave, Agriculture Prepaid, Agriculture Conventional |
| Midvaal Local Municipality | Non-Domestic Supplies, Non-Domestic Prepaid, Non-Domestic Two-Part, Off-Peak Tariff, Megaflex, Miniflex, Agricultural Standard, Agricultural Nite Save, Bulk Supplies |
| Mogale City Local Municipality | Commercial Small, Commercial Medium, Commercial Large Three Phase, Industrial Medium, Industrial Large, Commercial Medium - FlexiTime, Commercial Large - FlexiTime, Industrial Medium - FlexiTime, Industrial Large - FlexiTime |
Only per-kWh charges are used to value solar: the energy charge, plus a per-kWh surcharge where Red Energy has established that it varies with consumption. Time-of-use tariffs follow one season calendar — high-demand season June to August, low-demand season September to May — and, where a tariff publishes Peak, Standard and Off-Peak rates for both seasons, solar used directly is valued at the Standard rate and a battery's value in Peak periods is modelled, net of the cost of charging it. If your tariff is not listed, Red Energy can enter its rates manually.
For the full list of inputs, defaults, data sources and limitations, see how My Solar Plan works.
Frequently asked questions
Is commercial solar worth it in South Africa?
It is usually strongest for businesses that use a lot of electricity during the day, on a roof or site with good sun. The saving comes from grid energy the system replaces, so a site's daytime consumption and tariff matter more than its roof size. My Solar Plan gives an indicative answer for a specific property.
How much does commercial solar cost?
Price depends on the system size, the equipment, whether a battery is included, the roof and the electrical work. Red Energy prices a system from its approved equipment configuration after a site inspection. My Solar Plan does not show a price or payback period before then, rather than guess one.
What is payback and how is it calculated?
Simple payback is the priced system cost divided by the indicative annual saving. It is not a full investment appraisal. The saving counts only per-kWh grid charges solar actually replaces and excludes tariff increases, panel degradation, finance and tax. It also assumes the same average daytime use every day of the year, so for a business closed at weekends it overstates the saving and understates the payback period.
Does My Solar Plan work for factories, warehouses, farms and offices?
Yes. It is built for commercial and industrial sites in South Africa: large and multiple roofs, ground-mounted arrays, business operating patterns, commercial tariffs and backup requirements.
Build an indicative plan for your own site
My Solar Plan runs the same engine on your property: start with the address, confirm the roof, describe how the business uses electricity, then save the plan privately and refine it with Red Energy.
Start with my propertyLast reviewed 2026-10-13.