Ask most South African businesses how they sized their solar system, and the answer is usually "based on our average monthly electricity spend." That single number is the fastest way to end up with a system that either underdelivers on savings or is oversized for what the building actually uses — because an average bill hides exactly the information that determines commercial solar ROI: your load profile.
What a Load Profile Actually Shows
A load profile is a time-stamped record of how much electricity your business draws, typically in 30-minute or hourly intervals, across a representative period (ideally a full year, to capture seasonal variation). Where a monthly bill gives you one number, a load profile gives you a shape: when your demand peaks, how consistent your baseline draw is, and how much of your usage happens during daylight hours versus after dark.
For solar, that shape matters more than the total. A business that uses most of its electricity between 8am and 4pm on weekdays — a typical office, light manufacturing, or retail pattern — can self-consume a very high share of what solar generates, with minimal need for battery storage. A business running a second or third shift, or with most of its load happening after sunset, will see a much smaller portion of its usage offset by solar alone, and the ROI case shifts heavily toward whether batteries or a wheeling/PPA arrangement make more sense.
How This Distorts a Standard Quote
If an installer sizes your system off average monthly spend without a load profile, two things commonly go wrong:
- Self-consumption is overstated. The quote assumes you use most of what you generate, when in practice a meaningful share may be exported at a much lower feed-in credit (where available at all) or simply not credited.
- The battery recommendation is either arbitrary or absent. Without knowing your actual peak demand and evening load, sizing a battery — or deciding you don't need one — is guesswork dressed up as a recommendation.
The result is a payback period on paper that doesn't match the payback period in reality, discovered only after the system is installed and the first few months of bills come in lower-than-promised savings.
What to Ask For Before You Sign
If you're evaluating commercial solar, ask your installer or the quoting party for:
- A load profile pulled from your actual smart meter data (most municipalities and utilities can provide this on request, or your existing meter may already log it)
- A self-consumption percentage that's calculated from that load profile, not assumed
- A side-by-side of the ROI with and without battery storage, so you can see what the battery is actually buying you in payback terms
This is a different conversation to the one most commercial solar sales calls default to, and installers who are used to doing proper commercial system design will have this data ready without being asked twice.
Where a Generic Calculator Falls Short
Most public solar calculators, ours included, are built primarily around residential usage patterns and a monthly bill input — genuinely useful for a first, rough estimate of system size and payback for a business, but not a substitute for a load-profile-based commercial design. Use our solar calculator to get a starting figure for budget conversations internally, then insist on load-profile-based sizing once you're speaking to installers directly.
When you're ready for that conversation, you can compare vetted commercial solar installers on ADEO and ask each one directly whether their quote is based on your load profile or your average bill.
Frequently Asked Questions
How do I get my business's load profile? Ask your municipality or metering provider for historical interval data from your smart meter, or request it as part of the installer's site assessment — a proper commercial solar design shouldn't proceed without it.
Does a load profile change the panel count, or just the battery size? Both. It affects how much south/north-facing roof area is worth using, and it's the primary input for right-sizing (or ruling out) battery storage.
Is load-profile-based sizing worth it for a small business? It matters most once your monthly spend is high enough that a sizing mistake represents real rand value — for very small operations, the average-bill approach is a reasonable starting estimate, provided you treat it as a starting estimate and not a final design.
Writes about solar and renewable energy for South African homes and businesses at SolarTally, and cross-checks every guide against current tariffs and installer standards.
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