Posted on June-06-2026
Welding often takes place in environments where access to mains electricity simply isn’t possible. Whether you’re working on a construction site, carrying out repairs in remote locations, or handling mobile welding jobs, a generator becomes essential.
But one of the most common questions we hear at Arc Welding Services is:
“What size generator do I actually need for welding?”
Choosing the wrong generator can lead to poor weld quality, equipment damage, or even complete power failure mid-job. In this guide, we’ll break everything down in a clear, practical way so you can choose the right generator with confidence.
Welding machines require a significant amount of power, especially during arc starts. If your generator is too small, you may experience:
Unstable arc performance
Poor weld penetration
Overheating equipment
Generator overload or shutdown
On the other hand, an oversized generator means unnecessary cost, fuel consumption, and inefficiency.
The goal is to find the right balance between power, performance, and efficiency.
Before choosing a generator, it’s important to understand how power is measured.
kW (kilowatts) = Real usable power
kVA (kilovolt-amperes) = Apparent power
Most generators are rated in kVA, while welding machines are often rated in amps or kW.
As a general rule:
1 kW ≈ 1.25 kVA
So if your welder needs 8 kW, you’ll need roughly a 10 kVA generator.
The size of generator you need depends heavily on the type of welding you’re doing.
Lower power requirement
Common for site work and repairs
Typically needs: 5–10 kVA generator
Moderate power usage
Requires stable voltage
Typically needs: 8–15 kVA generator
More sensitive to power fluctuations
Requires clean, stable output
Typically needs: 10–20 kVA generator
High amperage machines
Continuous operation
Typically needs: 20 kVA+ generators
Your welding amperage plays a huge role in generator sizing.
Here’s a simple guideline:
Up to 150 amps → 5–7 kVA generator
150–200 amps → 7–10 kVA generator
200–300 amps → 10–15 kVA generator
300+ amps → 15–25+ kVA generator
The higher the amperage, the more power your generator must supply.
Welders draw more power when starting the arc than during continuous welding.
This is called peak load, and it’s where many people go wrong.
If your generator can’t handle that surge:
The arc may fail to start
The generator may trip or stall
Always choose a generator with at least 20–30% extra capacity above your welder’s requirement.
Not all generators are created equal.
For welding, especially TIG or inverter-based machines, you need:
Stable voltage output
Low harmonic distortion
Consistent frequency
Poor-quality generators can lead to:
Erratic welds
Equipment damage
Reduced lifespan of your welder
Inverter generators or high-quality diesel generators are usually the best option.
Your working conditions will also influence your generator choice.
Durable diesel generators preferred
Weather resistance is important
Compact, portable generators
Easy transport between jobs
Larger standby generators
Continuous duty capability
This is the most common issue and leads to poor weld quality and equipment strain.
If you’re welding continuously, your generator must handle sustained loads, not just short bursts.
This can damage sensitive welding equipment and affect results.
Always leave extra capacity for safe and reliable operation.
Not necessarily.
If you’re working in Birmingham or the West Midlands, it may be more efficient to use:
Professional mobile welding services
On-site welding specialists with the right equipment
At Arc Welding Services, we often see businesses overspending on equipment when a professional service would be faster, safer, and more cost-effective.
Hiring a generator or welding service is often the better option when:
You only need it for short-term projects
You’re unsure about the correct setup
You want to avoid maintenance and fuel costs
You need guaranteed performance on-site
Choosing the right generator for welding comes down to a few key factors:
Your welding process (MIG, TIG, MMA)
Required amperage
Peak power demands
Working environment
Getting this right ensures:
Better weld quality
Longer equipment lifespan
Safer, more efficient operation
Unsure if your current generator can handle your next site job? Or need to hire a mobile welding rig in the West Midlands? Contact the Arc Welding Services team today on 0121 327 2249 or complete our online contact form.
