5 Practical Tips for Buying a Diesel Generator

Generators are the backbone of construction sites, events, and industrial sites. Whether you’re buying to support a site in Germiston or anywhere in South Africa, use these five concise, action-oriented tips to pick the right diesel generator — the first time.

TIP 1 — Size the generator correctly (and don’t oversize by default)

Sizing isn’t just kW. Motor starting (inrush) currents, harmonics from VFDs, and sensitive loads change the real requirement.

  • Estimate running load (kW) first; then account for starting kVA for motors and transformers.
  • Ask: are there VFDs, sequential starts, or sensitive electronics that need tighter voltage/frequency control?
  • Consider alternator excitation options (permanent magnet or auxiliary winding) and D-AVR controllers — they reduce the need to oversize by improving transient response.
  • If you have transformers or medium-voltage systems, ask about “Close Before Excitation” systems for softer magnetising starts.

Result: accurate sizing → lower fuel use, less wear, longer service intervals.

TIP 2 — Choose modular / parallel-capable equipment

Even if you buy one unit now, check whether the set can be paralleled later.

  • Confirm whether parallel controls are built-in or available as an add-on.
  • Ask: how long does commissioning to parallel mode take? (Some systems are plug-and-play and take <10 minutes; others need lengthy setup.)
  • Benefits of modular sets: improved fuel efficiency, staged start/stop by load, and redundancy when a unit fails.

Use case: multiple 325 kVA sets running in sequence will often be more fuel efficient and flexible than one oversized 1 MVA set.

TIP 3 — Insist on a modern control & power management system (PMS)

A modern control system pays back fast.

  • Look for remote start/stop, alarm telemetry (low fuel, high temp), and runtime/fuel reports.
  • Prefer plug-and-play PMS for rental or multi-unit sites — it automates which sets run and protects engines from low-load damage.
  • Ensure the control supports load-shedding strategies, scheduled testing, and easy service logging.

Outcome: better uptime, easier diagnostics, and lower operating cost.

TIP 4 — Compare fuel consumption and autonomy

Fuel is a large portion of operating cost — quantify it before you buy.

  • Request manufacturer fuel-consumption curves at typical load points (25%, 50%, 75%, 100%).
  • Check tank size and refuelling logistics for your site: how long can the unit run unattended?
  • Ask about alternative fuels (natural gas, biogas) if emissions or supply security are priorities.

Practical check: get two or three manufacturer fuel forecasts for the same duty cycle and use them when modelling OPEX.

TIP 5 — Confirm transport, handling, and site footprint

Physical features matter for logistics and ongoing costs.

  • Verify lifting eyes, forklift pockets, and tow options.
  • If space is tight, ask whether units stack or are available in compact enclosures.
  • Consider sound-attenuated (silent) options if the install is near people or sensitive sites.

Small design choices → lower transport costs, faster site deployment.

Technical checklist

  • Running kW estimate
  • Motor starting strategy (soft start / D-AVR / PM alternator)
  • Parallel capability (yes/no + commissioning time)
  • Fuel consumption at duty cycle
  • Control/PMS features (remote monitoring, alarms, load management)
  • Lifting/transport features and acoustic specification

Conclusion

Sizing and control choices matter more than “bigger is better.” Modular, parallel-capable sets with modern PMS and good fuel data typically deliver the lowest lifetime cost and best reliability.