Running Generators in Parallel

Generators running in parallel are about flexibility, electrical resilience and smarter load management. Whether backing up critical systems or scaling power on demand, paralleling gives you options that a single unit can’t. But this strategy only works if you know what you’re doing — voltage machining, load sharing, and sync parameters must all be tight. With the right generators and supplier, you can create a powerful system.

Advantages of Paralleling Generators

There are many advantages to setting up a system of parallel generators for your facility. These advantages include:

• Redundancy: Adding a source of redundant power as backup is a great way to ensure mission-critical applications never fail. Redundancy can be vital to the success of business operations, industrial applications, and facilities such as data centers, manufacturing plants, processing plants, medical, hospital, emergency centers, and so on.
• Flexibility: A system of paralleling generators allows for easy alterations if needed. For example, if your facility takes on additional tasks that require backup power, the addition of another small unit to your system is much easier and less expensive than replacing a whole generator.
• Reliability: In case one of your backup generators malfunctions for any reason, a paralleling system means other units will still be available to kick in, providing essential power. Generator paralleling is much more fail proof than a stand alone emergency generator.

Running generators in parallel is a cost-efficient way to protect essential functions of your home or business from power loss. In addition to added protection against power loss, generator paralleling can be more efficient as they don’t all need to run at the same time.

How to Parallel Generators

Paralleling generators is more than wiring two machines together — you need a clear plan, the right hardware and proper synchronization. Here’s how to do it from planning to testing:

1. Assess and Plan

Start with your load requirements. Consider future scalability, site layout, fuel type, noise restrictions and how critical uptime is. Planning also includes understanding local regulations, grounding requirements and breaker coordination. Key considerations include:

• Duty cycle
• Total kilowatt (kW) or kilovolt-ampere (kVA)
• Site constraints
• Load type

2. Select Generators

Whether you run two or three generators in parallel, they must be compatible in voltage, frequency, phase sequence and output characteristics.

Several factors have to match for paralleling to work, including the phase number and rotation, which, when matched, avoid power surges and electro-mechanical stress. The generators’ frequency ratings need to match exactly, as well (60 Hz in the U.S.). The major advancements in digital control panel monitoring systems made recently allow for the exact synchronization of your system’s performance, with dedicated “paralleling switchgear” available to check the several microcontrollers installed in the multiple generator systems. Engine speed control, voltage regulation and load balance all need close monitoring to prevent damage to the system and failure.

Ideally, use identical models. Otherwise, opt for the same model with different specs. The generators should have similar voltage, phase, and frequency and be properly synchronized. They should also use the same fuel type to avoid potential damage.

3. Design the Parallel System

Designing a parallel system includes electrical, mechanical and control design. You’ll need a switchgear capable of paralleling, protection relays, bus bars, grounding and cable sizing. The control system should handle synchronization, load sharing and fault management. Include provisions for both automatic and manual operation if needed.

Core components include:

• Circuit breakers
• Load transfer logic
• Proper grounding and bonding
• Paralleling switchgear or control panels

4. Install Generators

Generator placement needs to allow air flow, maintenance access and safe cable routing. Fuel, exhaust and control wiring should be run separately to reduce electromagnetic interference (EMI), which is unwanted electrical noise that can disrupt the system’s operation. Properly rated cables should be used to connect to the switchgear or common bus. Install grounding per NEC and local code.

5. Synchronize the Setup

Most modern systems use automatic synchronization through the control panel, but if you need to run a manual sync, use a synchroscope and voltage or frequency meters.

6. Configure the Load Sharing

Once synchronized and connected, generators must share the load proportionally to their capacity. This is managed by droop or isochronous load sharing controls, which are often done through a governor controller and load-sharing lines or CAN-based digital communication.

7. Test the System

Run functional tests before going live. Simulate loads, test transitions, verify alarm and shutdown systems and ensure all generators share properly under different conditions. Include both no-load and full-load testing, documenting the setup to train staff on safe operation and troubleshooting.

Factors to Consider When Paralleling Generators​

Paralleling two or more generators is expensive and very complex. To limit these added difficulties, professionals recommend that generators of similar make and rating be used and that you use the services of a qualified electrical professional.

There are many reasons to run generators in parallel, whether to seamlessly replace an old unit with a new one without loss of power or to run parallel to the utility power source to feed surplus power back to the grid. Whatever the case, the decision to build a multi-unit system running in parallel is best made after considering all of these factors and more.

How Woodstock Power Company Can Help

Paralleling generators is simpler when you know and follow the rules. It gives you modularity, built-in backup and more uptime with less risk. Whether you’re trying to reduce idle capacity or just need a scalable solution for fluctuating loads, this is how you make your generator fleet work smarter.

We’re a Philadelphia-based company with many years of experience in the generator business and have built relationships with professional electricians worldwide. We can guide you in making the best decisions when designing your backup power system. If you have any questions regarding generators or parallel connection of generators​, fill out our contact form or call us at 610-658-3242 for more information on running generators in parallel.