A Comprehensive Guide To Determining The Right Size For Your Generator

Generators are the backbone of backup power solutions, ensuring that businesses and homes continue to function seamlessly during power outages. However, selecting the right generator size is a critical decision that requires careful consideration of various factors. In this comprehensive guide, we'll explore the key steps to determine the right size for your generator, covering aspects such as load sizing, generator classes, fuel considerations, and maintenance practices.

How To Size A Generator

Understanding the power needs of your equipment is the foundational step in sizing a generator correctly. The total wattage required by your appliances and machinery will determine the minimum electrical input needed from a generator. Here are the essential steps:

Calculate The Load Size

You need to know exactly what your generator needs to support during a power outage. This might be as small as a single piece of equipment, or it may be keeping a whole building going for business as usual. Here’s how to do this: 

Make a List: Enumerate all the equipment you need to power during an outage.

Wattage Calculation: Find and add up the total wattage for each item. This information is typically available on the equipment's nameplate or in the manufacturer's guide.

Consider Starting Wattage: Some equipment has different starting and running wattage due to the initial surge required. Factor in these variations to avoid underestimating the generator size needed.

Convert kW to kVA

Determine kW: Calculate the total power requirement in kilowatts (kW) from the maximum required wattage.

Consider Power Factor (Pf): Generators are rated in kilo-volt-amperes (kVA). Assess the power factor, usually rated at 0.8, to convert kW to kVA accurately. A generator with 0.8pf may not be sufficient if your equipment demands 100kW of actual power.

Define Your Running Requirements

Primary or Standby: Decide whether the generator will be the primary power source or a standby measure.

Operational Capacity: Generators should not be operated at maximum capacity for more than 30 minutes. Size for 70-80% capacity for primary power sources to enhance performance and accommodate future power requirements.

Where Is The Generator Needed?

The output required from the generator isn’t the only thing you’re going to need to consider when choosing a generator. Let’s take a look: 

Load Diversity: Assess the likelihood of all electrical equipment running simultaneously. Grouping equipment with non-overlapping operational times can lead to more efficient generator sizing.

Load Management: Implement effective load management practices, such as load shedding or prioritising essential equipment. This optimisation ensures efficient generator operation without overloading.

Climate and Environmental Factors: Environmental conditions, such as extreme temperatures, altitude, and humidity, can impact generator performance. Choose a generator size that accounts for these factors, especially in regions experiencing challenging weather conditions.

Installation location: You’ll need to consider the installation location when choosing between outdoor and indoor generators. Outdoor generators are ideal for areas with suitable outdoor space, and these generators can run as long as necessary during power failures. You’ll need to ensure proper protection and ventilation, especially in residential areas. Indoor Generators require careful consideration for ventilation, exhaust, and heat extraction. Compliance with regulations is crucial to prevent safety issues.

Petrol Generator vs. Diesel Generator?

When choosing between fuel types, you’ll need to consider factors like cost, fuel consumption, and suitability for specific uses. Here’s a quick overview of the pros and cons of each.

Petrol Generators tend to have a lower initial purchase cost; however, they may have higher fuel consumption for extended use. They are usually light and compact, so can be suitable for portable applications.

Diesel Generators usually have a higher upfront cost, but they have better performance for longer periods of use, as they are more fuel-efficient. This makes them suitable for permanent backup power.

Remember that the specific needs of your business may mean that the right generator for you isn’t the obvious one. It is well worth consulting experts to ensure you get the best solution for your setup.

Choosing The Best Size Generator For Your Business

Selecting the right size generator is essential for future-proofing critical electric loads. Consider factors such as load size, storage space, fuel, installation conditions, environmental considerations, and generator types before making a purchase.

A brand new generator is an investment for your business, and getting the best one for your needs is essential. But when budgets are tight, brand new may be out of reach. In this instance, buying a used generator may be the best solution – especially if you can source one with a full maintenance history. You can read more about buying used generators here.

How P&I Can Help

Choosing the right generator involves a detailed understanding of your power needs, load diversity, and environmental conditions. If you’re in the process of buying a generator, we highly recommend seeking professional advice. The team at P&I are specialists in generators, and we can advise you about planning for future expansion, as well as providing routine maintenance that helps to ensure reliable and efficient generator performance. Just get in touch - whatever the reason you’re looking for a generator the right generator size is critical for a seamless and uninterrupted power supply.