Temporary power looks like a simple hire decision until it is wrong. Undersize the set and you trip out under load. Oversize it and you burn fuel running a machine at a load factor it was never designed for.
1. Start with the actual load
Add up what will genuinely run at the same time, and separate continuous load from starting load. Motors, pumps and compressors draw far more on start than they do running, and that inrush determines whether a set copes.
Tip: Size for the largest starting load plus everything already running, not the sum of the nameplates.
2. Run the set in its efficient band
Diesel generating sets are designed to work. Running one at a very low load factor for extended periods causes:
- Wet stacking and glazed bores
- Additional unplanned maintenance
- Poor fuel economy per unit of useful output
3. Fuel, refuelling and runtime
Work out how long the set needs to run unattended and size fuel storage to match, with a sensible margin. Factor in who refuels, how often, and whether the site can be accessed safely at that time.
4. Site conditions change the answer
- Ambient temperature and altitude affect output
- Dust and noise limits affect placement
- Cable run length affects voltage drop
Tip: Confirm response expectations and servicing during the hire before the set arrives, not after something goes wrong.
Final thoughts
The right set is the one matched to your actual load, your site and your runtime — not the biggest one available.
