A diesel-solar hybrid uses PV (and often batteries) to cover daytime load while a generator handles night, cloud and motor starts. Controllers prevent reverse power and keep the engine in an efficient load band. Typical fuel savings of 40–70% are realistic on sites that previously ran diesel 12–24 hours per day.
Why this decision matters
A diesel-solar hybrid uses PV (and often batteries) to cover daytime load while a generator handles night, cloud and motor starts. Controllers prevent reverse power and keep the engine in an efficient load band. Typical fuel savings of 40–70% are realistic on sites that previously ran diesel 12–24 hours per day. 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 150 kVA Cummins 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 2026-08-05.
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 250 kVA site fuel effect
| Mode | Diesel h/day | Relative fuel | Notes |
|---|---|---|---|
| Diesel only | 14 | 100% | Baseline lodge/mine camp |
| PV assist | 8–10 | 55–70% | Daytime offset |
| PV + battery | 4–7 | 30–50% | Depends on BESS kWh |
Figures are indicative. Last updated 5 August 2026.
Frequently asked questions
What savings are realistic?
40–70% fuel on long-hour sites is a common planning band with proper design.
Do I still need a big generator?
Often yes for night and motor starts — hybrid cuts hours, not always peak kVA.
Battery chemistry?
Site dependent; cycle life and temperature matter more than brochure peaks.
Reverse power risk?
Controllers must protect the alternator — non-negotiable.
Where to read more?
See /solar-and-hybrid-power/ and the diesel-solar child page.
Related tools: Running cost calculator · All insights
Related sizes, categories and services: 150 kVA generators, 250 kVA generators and petrol generators.
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