What is the difference between running watts and starting watts?

Running watts is what a device draws once it is going. Starting watts is the brief surge a motor pulls to get moving, often three to seven times higher. A generator has to survive the surge, not just the average.

Should I add a safety margin?

Yes. Most rental specialists size at roughly 20 to 25 percent above the calculated peak so the unit is not running flat out for weeks.

Is a bigger generator always safer?

No. Diesel units run badly under very light load and can wet-stack over time. Oversizing also costs more in rate and fuel. Right-sized beats oversized.

Sizing

What size generator do you need?

Sizing is where most rental money is wasted. Build a load list, account for motor starting, then add a working margin.

Rough sizing reference
Size	Typically covers	Common fit
2 - 5 kW	Fridge, lights, phones, a sump pump, small hand tools	Home essentials, RV, DIY
5 - 10 kW	Several circuits, well pump, one small HVAC unit	Home backup, small crews
10 - 25 kW	Whole small home, small shop, light towers	Residential standby, small sites
25 - 60 kW	Mixed tools, small chillers, office trailers	Job sites, small commercial
60 - 150 kW	HVAC packages, pumps, production power	Construction, events
150 - 500 kW	Building standby, industrial motors	Facilities, industrial
500 kW +	Campus, data center, utility support	Large industrial, emergency response

These ranges are general industry guidance, not a quote or a specification for your site. Actual sizing depends on your equipment nameplates, voltage, phase and duty cycle.

Sizes people rent most

Each page below covers what that output realistically runs, the amps it produces at common voltages and what the site has to provide.

20 kW generator rental
About 25 kVA · Small job sites, residential standby through a transfer switch, market stalls
25 kW generator rental
About 31 kVA · Small commercial jobs, food vendors, medium home standby
50 kW generator rental
About 63 kVA · Active construction sites, mid-size events, retail standby
75 kW generator rental
About 94 kVA · Busier sites, larger productions, planned facility work
100 kW generator rental
About 125 kVA · Larger construction, facility standby, festivals
150 kW generator rental
About 188 kVA · Facilities, industrial temporary capacity, large events
200 kW generator rental
About 250 kVA · Commercial buildings, manufacturing, planned shutdowns
300 kW generator rental
About 375 kVA · Industrial sites, hospitals and campuses during planned work
500 kW generator rental
About 625 kVA · Industrial, utility support, emergency response