Generator sizing is one of those decisions that looks simple until you get it wrong. Order too small and you're dealing with overloaded circuits, voltage fluctuations, and equipment that won't start reliably. Order too large and you're paying to run a unit at 20% load — which isn't just wasteful, it's actually hard on the generator itself. Getting the sizing right the first time requires understanding a few fundamentals that don't always make it into the conversation when equipment gets ordered under time pressure.
This guide is aimed at project managers, site supervisors, and facility leads making real decisions about temporary or permanent power for industrial applications — not a theoretical exercise, but a practical framework for arriving at the right number.
Start With Load, Not With Generator Size
The most common mistake in generator sizing is starting with the generator rather than the load. Someone decides they need "a 100 kW unit" based on what a similar project used two years ago, or what the rental yard had available, without actually working through what the site is drawing. Sometimes that works out. Often it doesn't — because site loads vary significantly based on equipment mix, operational phase, and how many things are running simultaneously.
The right starting point is a load list: every piece of electrical equipment on site, its running wattage or kilowatt draw, and whether it runs continuously or intermittently. Running load is what the generator needs to sustain. Starting load — the surge demand when motors and compressors kick on — is often two to three times the running draw and is what actually determines the minimum generator capacity required.
If your site has several motors starting in sequence, a significant HVAC load, or large compressors cycling on and off, the starting load calculation matters more than the running load number. Undersizing based on running load alone is the most reliable way to end up with a generator that trips out every time the compressor starts.
Understanding Power Factor in Industrial Settings
Running load calculations also need to account for power factor — the ratio of real power (kW) to apparent power (kVA). Most industrial loads are inductive, meaning motors, pumps, and compressors draw more apparent power than their kW rating suggests. A generator rated at 100 kVA at 0.8 power factor delivers 80 kW of real power. If your load list totals 80 kW of inductive loads, you're already at the ceiling — with no headroom for starting surges or load additions.
This is a detail that gets glossed over in a lot of generator conversations, and it's one of the reasons that working through sizing with a knowledgeable provider matters. NexSource Power's electrical and instrumentation team can work through load calculations with you — accounting for power factor, starting loads, and future load additions — before a unit gets dispatched to site.
General Sizing Benchmarks for Common Industrial Applications
While every site is different, some general benchmarks help orient the conversation. Small construction sites running lighting, power tools, and a site trailer typically land in the 20–60 kW range. Mid-sized operations with welding equipment, multiple power circuits, and HVAC requirements generally sit between 60–150 kW. Larger industrial applications — wellpad facilities, processing equipment, remote camps with significant electrical loads — often require 200 kW to 500 kW or more, sometimes with multiple units running in parallel to provide both the capacity and the redundancy the operation requires.
These are starting points, not answers. A 150 kW site with three large motors starting simultaneously may actually need a 250 kW generator to handle the inrush current without voltage collapse. A 300 kW average load with a flat, predictable draw profile may run comfortably on a properly sized 350 kW unit. The specifics matter more than the category.
NexSource's industrial generator rental fleet runs from 20 kW through to 1 MW, covering the full range of temporary power requirements across construction, oilfield, mining, agriculture, and industrial facility applications in Alberta.
Redundancy and Paralleling: When One Unit Isn't Enough
For critical operations where power interruption carries serious consequences — continuous processing facilities, remote camps in winter conditions, active wellpad operations — single-generator configurations carry inherent risk. If the unit goes down for service or an unplanned fault, the site goes dark.
Paralleling two or more smaller generators addresses that exposure. Running two 200 kW units in parallel to serve a 300 kW load means that if one unit requires attention, the other carries the critical load while the issue gets resolved. It also allows load to be balanced across units more efficiently than a single oversized generator running at partial capacity.
This is a more sophisticated power system design than simply dropping a single unit on site, and it benefits from load management and power system engineering support to configure correctly. Done well, a paralleled generator setup is more reliable, more fuel-efficient, and more adaptable to load changes than a single large unit.
Fuel Type: Diesel vs. Natural Gas for Industrial Sites
Sizing isn't purely about kilowatts — fuel type affects the practical performance of the unit in Alberta's operating conditions. Diesel generators are the default for sites without a gas supply, offer reliable cold-weather starting, and pair naturally with on-site fuel storage and management solutions. Natural gas generators make strong economic sense for sites with an existing gas supply, eliminating fuel delivery logistics and often reducing operating costs over extended runtimes.
For oilfield applications specifically, natural gas units running on field gas are a well-established approach that reduces diesel consumption and simplifies fuel management across a multi-unit installation. The right fuel type depends on what's available at the site, the expected runtime, and the cost structure of the project.
When to Buy vs. When to Rent
Once you've landed on the right size and configuration, the rent-versus-buy question follows naturally. For project-specific or temporary power needs — construction phases, planned shutdowns, seasonal peaks, emergency backup — temporary generator rental is typically the operationally and financially sound choice. For permanent facility power where the unit will run continuously for years, industrial generators for purchase make more sense, spreading capital cost across a long utilization horizon.
Many operations have a mix of both — a permanent base load unit and rental capacity brought in during peak demand or maintenance windows. Managing that distinction deliberately is part of what separates lean, efficient power cost structures from ones carrying unnecessary overhead.
Talk to NexSource Before You Commit to a Size
The worst time to discover a generator is undersized is after it's on site and failing to hold load. The right conversation happens before the equipment is ordered — when there's still time to work through the load list properly, account for starting surges and power factor, and confirm the configuration matches what the site actually needs.
NexSource Power operates across Red Deer, Edmonton, Grande Prairie, and Drayton Valley with a rental fleet, sales inventory, and a technical team that can take a site load list and turn it into a properly sized, correctly configured power generation solution for any industrial application in Alberta. Contact NexSource before the equipment gets ordered — it's a much easier conversation at that stage
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