Standby rating is for emergency use with varying load and limited annual hours. Prime allows unlimited hours at variable load with 10% overload capability for short periods. Continuous is baseload at constant load with no overload. Mis-selling a standby set into prime duty is the fastest way to void a warranty in SADC markets.
Why this decision matters
Standby rating is for emergency use with varying load and limited annual hours. Prime allows unlimited hours at variable load with 10% overload capability for short periods. Continuous is baseload at constant load with no overload. Mis-selling a standby set into prime duty is the fastest way to void a warranty in SADC markets. 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 kVA to kW converter and a specialist review before you issue a purchase order. Catalogue pages for the 60 kVA Perkins prime and 500 kVA Baudouin industrial 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 2026-06-30.
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
ISO-style rating summary
| Rating | Hours/year | Load profile | Overload |
|---|---|---|---|
| Standby | Limited | Variable emergency | Typically none |
| Prime | Unlimited | Variable | 10% limited time |
| Continuous | Unlimited | Constant baseload | None |
Figures are indicative. Last updated 30 June 2026.
Frequently asked questions
Can I run standby 12 hours a day?
Not within rating intent — expect shortened life and warranty risk.
Is prime the same as continuous?
No. Continuous is constant baseload without overload allowance.
How do nameplates show this?
Look for ESP/PRP/COP style markings and the OEM datasheet footnotes.
What do mines usually specify?
Prime or continuous bias with realistic ambient derates.
Does canopy type change rating?
Cooling and airflow can limit output — follow packaged genset datasheets.
Related tools: kVA to kW converter · All insights
Related sizes, categories and services: 60 kVA generators, 500 kVA generators and petrol generators.
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