Diesel Generator Buying Guide

What to consider before you buy — so the generator fits your load, site, and application

A practical, brand-independent guide to choosing a diesel generator set: standby vs prime, sizing, frequency, ATS, and the conditions that affect output.

PRE-ORDER CHECKLIST ↓ GET A QUOTE →

Start With the Application

🔋

Standby / Backup

Runs only during outages. Needs an automatic transfer switch (ATS) to start and transfer the load automatically. Lower purchase cost, limited annual running hours.

⚡

Prime / Continuous

The main power source for off-grid sites. Built for continuous duty with unlimited running hours, at a higher cost than a standby-rated unit.

📐

Sizing

Add the running load plus the starting surge of motors (about 3× running current), then leave a margin for future growth. Never under-size a standby set.

Pre-Order Configuration Checklist

Work through these nine points before you order. Each one changes the engine, enclosure, or controls you need.

Installation Type

Outdoor silent (canopy) for low noise and weatherproofing, or open frame installed in a dedicated, ventilated machine room.

Frequency

Confirm your grid frequency: 50 Hz or 60 Hz. Engine speed and alternator wiring differ, so specify this up front.

Standby Needs an ATS

Standby and backup applications require an automatic transfer switch (ATS) to start the generator and transfer the load without manual intervention.

Prime Duty Limit

For prime (main power) applications, confirm the duty rating — continuous prime vs limited-time running (e.g., 12-hour) ratings.

Cold Climate

Cold regions need an engine pre-heater (block or coolant heater) to ensure reliable cold starting.

Altitude & Temperature

Above 1,000 m altitude or 40 °C ambient, the engine de-rates. Specify your site conditions so the set is sized and derated correctly.

Coastal Corrosion

Coastal or marine sites need C4/C5 anti-corrosion treatment on the enclosure and fittings to resist salt-laden air.

Motor Loads

If the load includes large motors or pumps, they need a soft start or the generator must be oversized to absorb the starting surge.

Paralleling

Running multiple sets together for redundancy or capacity requires a paralleling cabinet to synchronize and share load safely.

Frequently Asked Questions — Buying a Diesel Generator

What should I consider before buying a diesel generator?+

Confirm the application (standby vs prime), size the unit to your running and motor-starting load, choose the frequency (50Hz or 60Hz), and decide on installation type and engine brand. Work through the 9-point pre-order checklist on this page before ordering.

Do I need an automatic transfer switch (ATS)?+

For standby or backup applications, yes. The ATS detects a utility outage, starts the generator, and transfers the load automatically. For a prime-power application running continuously off-grid, an ATS is not required.

What is the difference between an open and a silent generator?+

An open (open-frame) generator is lower-cost and needs to be installed in a dedicated, ventilated machine room. A silent (canopy) generator is weatherproof and noise-dampened for outdoor installation closer to occupied areas.

How do altitude and temperature affect generator output?+

Above 1,000 m altitude or 40 °C ambient temperature, a diesel engine de-rates — it produces less power than its nameplate. The generator must be sized to account for these conditions, or the engine derated accordingly.

Tell us your application, load, and site conditions — we'll recommend the right generator and configuration.

GET A GENERATOR QUOTE →