How to choose the right diesel generator for your business?

Need backup power? Choosing a business generator is important. Pick the wrong one, and you have problems.

Selecting a business diesel generator requires determining correct power size, evaluating installation site needs, and considering long-term operational costs beyond the initial price.

It is a big investment.

Let us get it right.

How is Proper Power Output Determined for a Business's Needs?

How much power does your business really need from a generator?

Determining the correct generator size means calculating your total power requirement¹, accounting for starting loads², and selecting a unit with enough capacity in both kW and kVA.

Calculating Your Business's Power Needs

Getting the generator size right is step number one. If the generator is too small, it will be overloaded. This can damage the generator and the equipment it powers. If it is too big, it costs more than you need to pay. It also might not run efficiently. Diesel engines run best when loaded properly. When running too light, they can have issues like wet stacking. So, getting the power output³ correct is very important. Generators have two main power ratings: kW and kVA. kW is Kilowatts. This is the real power. It is what does the actual work. kVA is Kilovolt-Amperes. This is the apparent power. It includes both real power (kW) and reactive power. For most businesses, you need to look at both. The relationship is kW = kVA * Power Factor. The Power Factor is usually between 0.8 and 1. For most equipment, especially motors, the power factor is less than 1. This means you need a generator rated in kVA that is higher than the total kW load, especially if you have many motors. I always tell my M&E contractor clients to look at both ratings on the generator nameplate and compare them to the load.

To figure out your total power need, you need to list all the equipment you want the generator to power. Find the power consumption for each item. This is usually on the equipment nameplate or in the manual. It might be listed in Watts (W), Kilowatts (kW), Amps (A), or Horsepower (HP). Convert everything to Watts or Kilowatts. Add up the power for all the equipment that will run at the same time. This gives you the total running load. But you also need to think about starting loads. Some equipment, especially electric motors (like those in air conditioners, pumps, or fans), draw a much higher current when they start than when they are running. This is called the starting surge or inrush current. The generator must be able to provide this surge for each piece of equipment that might start while other equipment is already running. You need to identify the largest motor or group of motors that will start at the same time. Calculate their starting load. Generator manufacturers provide guides or software to help estimate starting loads. Sometimes, the starting load of one large motor can be several times its running load. The generator must handle the total running load plus the largest starting surge at any moment.

Steps to Determine Power Size

• List All Loads: Make a list of everything the generator will power.
• Find Running Watts/kW: Get the power consumption for each item when running.
• Find Starting Watts/kVA: Identify items with high starting surge (mostly motors) and find their starting power.
• Calculate Total Running Load: Add up the running power of items that run together.
• Calculate Max Starting Load: Determine the largest surge needed at any one time.
• Add Safety Margin: Add 10-20% margin to your total calculated load.
• Consider kW and kVA: Ensure the generator rating meets both your real and apparent power needs.

From my experience working with clients on generator projects, it is often best to slightly oversize the generator rather than risk underrating it. A little extra capacity provides flexibility for future growth and handles unexpected load variations better. A load study using a clamp meter on your current power source can also give you a clear picture of your actual power usage, including surges. For project procurement partners, providing a detailed list of all equipment with power ratings to the supplier is crucial. We can help calculate the required generator size based on that information. We use our knowledge of different engine and alternator capabilities to recommend the right kVA and kW rating for reliable operation, ensuring the generator can handle both the steady load and the starting surges common in industrial and commercial settings.

So, calculate your total running power, account for the highest starting power, and pick a generator with enough kW and kVA capacity plus a little extra room.

What Site-Specific Requirements Must Be Evaluated During Selection?

Does your business location affect the type of generator you need?

Site conditions like where the generator will be installed, how it gets fresh air, where exhaust goes, noise limits, and fuel storage rules are critical factors in choosing the right unit.

Evaluating Your Installation Site

Once you know the size of the generator you need, you must look at where it will go. The installation site has a big impact on the generator choice and setup. First, decide if the generator will be indoors or outdoors. Outdoor generators usually come in soundproof and weather-resistant enclosures. These protect the generator from rain, snow, and sun. Indoor generators need a dedicated room. This room must have good ventilation. The engine produces a lot of heat. It also needs air to burn the fuel. So, the room needs inlets for fresh air and outlets for hot air. The exhaust fumes must also be safely vented outside. This is usually done with an exhaust pipe through a wall or roof. Incorrect ventilation can cause the generator to overheat and shut down. It can also lead to engine problems.

Noise is another important factor. Diesel generators can be noisy. If your business is in a populated area or has noise restrictions, you might need a generator with a special sound-attenuated enclosure. These enclosures significantly reduce the noise level. They are often measured in decibels (dB). Standards might require noise levels below a certain dB limit at a specific distance (e.g., 70 dB at 7 meters). For our clients installing generators near offices or residential areas, we always recommend a super silent type enclosure. This is a common request from distribution partners serving urban markets. Fuel storage is also a site requirement. Diesel fuel needs to be stored in tanks that meet local regulations. This includes tank capacity, material, location, and spill containment measures. For generators that need to run for long periods, you need a large enough fuel tank, either on the generator frame or a separate bulk tank. The location of the fuel tank relative to the generator and the method of getting fuel to the engine (e.g., a lift pump) must be considered.

Important Site Considerations

• Location: Indoors or Outdoors, Accessibility for Maintenance/Fueling.
• Space: Enough room for the generator, clearances for airflow and service access.
• Ventilation⁴: How air gets in and hot air gets out for cooling and combustion.
• Exhaust: Safe routing of engine exhaust fumes away from buildings and people.
• Noise⁵: Local regulations or neighbor considerations regarding noise levels.
• Fuel Storage⁶: Tank size, location, type, and compliance with local fire/environmental codes.
• Foundation: A level, stable base strong enough to support the generator's weight and vibration.

For project execution entities, evaluating the site early is key to avoiding problems later. Will the generator fit? Can we get fuel to it easily? Is there enough ventilation? These questions need answers before the generator is ordered. I often help clients review site plans to make sure the generator configuration (like radiator orientation or exhaust pipe routing) will work. For distribution partners selling to different types of businesses, knowing the customer's site constraints helps recommend the right enclosure, cooling system, and fuel tank options. For example, a generator for a rooftop installation needs different considerations (weight, crane access) than one going into a basement. My experience shows that ignoring site requirements leads to difficult and expensive fixes during installation.

So, look closely at where the generator will go. Make sure it has air, a place for exhaust, meets noise rules, and can store enough fuel safely.

What Long-Term Costs Influence Generator Selection Beyond Purchase Price?

Is the price tag the only cost to think about for a business generator?

Beyond the initial purchase price, the total cost of ownership includes long-term factors like fuel consumption, routine and unexpected maintenance costs, and the generator's expected operational lifespan.

Understanding the Total Cost of Ownership

Buying a generator is not just about the price you pay upfront. You will spend money on it over its entire life. This is called the Total Cost of Ownership⁷ (TCO). The initial price is a big part, but for a diesel generator that might run for thousands of hours, the running costs add up. Fuel cost is usually the largest ongoing expense. As I mentioned, diesel generators are fuel-efficient, but they still use a lot of fuel over time. You need to estimate how many hours per year the generator will run. Then, calculate how much fuel it will use during those hours. Generators have a fuel consumption rate⁸, often given in liters or gallons per hour at different load levels (e.g., 75% load, 100% load). Multiply the estimated running hours by the fuel consumption rate and the average price of diesel fuel. This gives you an estimate of your annual fuel cost. Over ten or fifteen years, this cost can be much higher than the original purchase price.

Maintenance costs are also part of TCO. Diesel generators require regular maintenance. This includes changing the oil, oil filters, fuel filters, and air filters at set intervals (usually based on running hours or calendar time). There are also less frequent items, like coolant changes, valve adjustments, and potentially injector or turbocharger service. You need to budget for these parts and the labor costs for a qualified technician. Unexpected repairs can also happen, though less likely with a well-maintained, quality generator. The expected lifespan of the generator engine and alternator is important too. Industrial diesel engines are built to run for tens of thousands of hours before needing major overhauls. A generator with a longer expected lifespan, even if its initial cost is higher, might be cheaper in the long run because you delay replacement costs. For our H&C generators, we use reputable industrial engines known for long life. This is a key point I emphasize to distribution partners and project clients; the quality of components directly affects TCO.

Components of Total Cost of Ownership

• Initial Purchase Price: The upfront cost of the generator and enclosure.
• Installation Costs: Labor, materials for setup, foundation, wiring, exhaust, fuel lines.
• Fuel Costs: The ongoing expense of buying diesel fuel based on usage.
• Routine Maintenance: Cost of filters, oil, coolant, and labor for scheduled service.
• Repair Costs: Expense for unexpected part failures or major overhauls.
• Monitoring/Control System: Costs for remote monitoring hardware or services.
• Expected Lifespan: How many hours/years the generator is designed to operate reliably.
• Decommissioning Costs: Cost to remove and dispose of the generator at the end of its life.

When talking with potential customers, especially project procurement partners who manage budgets, TCO is a crucial concept. A cheaper generator upfront might use more fuel, break down more often, or not last as long, costing more over its life. It is like comparing cars; one might be cheaper to buy but cost more in gas and repairs over the years. We provide documentation on fuel consumption rates and recommended maintenance schedules so clients can better estimate their TCO. Considering these long-term costs helps make a more informed decision and justifies investing in a quality generator built for durability and efficiency, like the ones we make. A good maintenance plan is not just about keeping the generator running; it is about protecting your investment and managing your TCO.

So, look past the purchase price. Figure out fuel costs, maintenance costs, and how long the generator will last. This gives you the true cost of ownership.

Conclusion

Pick size correctly, match site needs, and factor in long-term running costs.