Most of a generator’s lifetime cost is diesel, not the purchase price. At 75% load a 100 kVA set uses roughly 17–19 L/h; at R23.50/L that is over R400 per hour. Add scheduled services, filters, coolant and eventual major overhaul. Model five-year TCO before you choose engine brand or canopy type.
Why this decision matters
Most of a generator’s lifetime cost is diesel, not the purchase price. At 75% load a 100 kVA set uses roughly 17–19 L/h; at R23.50/L that is over R400 per hour. Add scheduled services, filters, coolant and eventual major overhaul. Model five-year TCO before you choose engine brand or canopy type. Buyers who skip structured sizing or compliance checks pay twice: once for the wrong unit, and again for downtime, fuel waste or a failed insurance claim.
AGP Generators engineers treat every enquiry as a load and site problem first, a product second. The notes below are the same framework we use on commercial RFQs across South Africa and SADC.
Practical method
Step-by-step
Start with a written load list: running watts, starting watts, duty cycle and which loads are truly critical. Convert watts to kVA using power factor (0.8 is the commercial default unless you know otherwise).
Apply site factors next — altitude derate, ambient temperature, fuel quality and whether the set will see prime hours or true standby. Only then shortlist engine brands and canopy types.
Validate with our Running cost calculator and a specialist review before you issue a purchase order. Catalogue pages for the 100 kVA Perkins silent and 250 kVA Perkins silent show real price bands excl. VAT to sanity-check budgets.
- Record running and starting loads separately for motors and compressors.
- Separate essential vs shedable circuits so you do not oversize the set.
- Confirm phase (single vs three) against the DB and utility supply.
- Document who owns installation, CoC and first service.
Reference data
Use the table as an indicative planning aid, not a substitute for a site assessment. Prices and fuel figures move with diesel wholesale rates and exchange rates — we re-verify commercial quotes at order stage. Last updated 2026-08-20.
Common mistakes
Copying the kVA of a failed set without measuring today’s load. Ignoring motor starting. Buying open-frame units for estate boundaries. Skipping changeover and earthing design. Assuming “silent” means inaudible indoors.
How AGP helps
We size, supply, install and maintain diesel and petrol generators from 2.2 kVA to 1000+ kVA. Request a quote with your load list, or call +27 41 007 0618. For hybrid and long-hour sites, ask about diesel-solar controllers that keep engines in an efficient band.
Data table
Example fuel cost at R23.50/L, 75% load
| kVA | L/h (indicative) | R/hour | R/8h day |
|---|---|---|---|
| 30 | 5.8 | R136 | R1,090 |
| 60 | 11.5 | R270 | R2,162 |
| 100 | 18.2 | R428 | R3,422 |
| 150 | 26.5 | R623 | R4,982 |
| 250 | 42 | R987 | R7,896 |
Figures are indicative. Last updated 20 August 2026.
Frequently asked questions
What load % should I model?
75% is a common planning point; real profiles vary — log hours and fuel if you can.
Does engine brand change fuel burn much?
Within a class, load and maintenance dominate; poor tune wastes more than badge differences.
How often is a major overhaul?
OEM hour limits vary; prime-duty sets reach them faster than true standby.
Include installation in TCO?
Yes — cable, plinth, changeover and CoC are part of year-zero cost.
Where do I get live diesel prices?
Use your supplier contract; our calculators default to a reference R/L you can edit.
Related tools: Running cost calculator · All insights
Related sizes, categories and services: 100 kVA generators, 250 kVA generators and petrol generators.
Get power insights by email
Sizing guides, compliance notes and running-cost updates. Unsubscribe any time — POPIA compliant.