Choosing the right generator can be overwhelming. Do you know how to pick the best one for your needs? Generator power ratings are key to making an informed decision. In this post, we’ll explain what generator power ratings are and why they matter. You’ll learn how to choose the right generator for your home, business, or industrial use.
Understanding the different types of generator power ratings is essential for selecting the right generator. There are a few key ratings you need to be familiar with, each serving a specific purpose in determining how well a generator performs in different situations.
eKW (electrical kilowatts) measures the generator's output after accounting for efficiency losses. These losses occur when mechanical energy is converted into electrical energy. This rating tells you how much usable power the generator provides after those losses.
Key Point:
The eKW rating is crucial because it helps you ensure that the generator can handle your equipment's energy needs. If the generator’s eKW is lower than what your equipment requires, it may not run properly. If it's higher than needed, you might waste energy and money.
eKW directly impacts how your equipment performs. If the generator doesn’t provide enough eKW, devices may underperform or fail to work at all. On the other hand, having excess eKW can lead to inefficiencies and higher operating costs.
eKW measures usable power, while kVA measures total power (including reactive power). Reactive power doesn't contribute to running equipment, so eKW is a more accurate representation of the generator’s ability to power devices.
Power Rating | What It Measures | Type of Power |
eKW | Usable electrical power | Real power (kW) |
kVA | Total electrical power | Real + Reactive power |
kVA (kilovolt-amperes) is used to measure a generator's total output, which includes both real power and reactive power. Reactive power supports voltage levels but doesn’t perform work, unlike real power, which powers equipment.
kVA helps determine whether a generator can handle varying loads. It’s especially important when you have equipment that requires large amounts of power for short bursts, such as motors or air conditioners.
A higher kVA rating means a generator can handle more equipment or larger loads. When selecting a generator, check if its kVA rating matches your peak power needs. This ensures it can handle both typical loads and unexpected spikes in demand.
To convert kVA to eKW, use the power factor. This value adjusts for the difference between total power (kVA) and usable power (eKW). Multiply the kVA by the power factor to get eKW:
eKW = kVA × Power Factor
For example, if you have a 10 kVA generator and a power factor of 0.8, the eKW would be:
10 kVA × 0.8 = 8 eKW
kVA Rating | Power Factor | eKW (Usable Power) |
10 kVA | 0.8 | 8 eKW |
15 kVA | 0.9 | 13.5 eKW |
Choosing the right generator depends on understanding different power ratings. These ratings help determine how long a generator can run and what types of loads it can handle. Let’s dive into the most common generator ratings: Standby, Prime, Continuous, and Limited Time power ratings.
Standby power is the backup power a generator provides during an emergency, like a power outage. It’s meant to keep essential equipment running until the main power source is restored.
Generators with standby power ratings can typically operate between 500 hours and a full year, depending on the specific model. They’re designed for occasional use during emergencies, not for continuous operation.
Power Rating | Operational Time | Use Case |
Standby Power | 500 hours to 1 year | Emergency backup |
Standby generators are ideal for situations where you need power temporarily but expect the grid to return soon. They are used in homes, hospitals, and small businesses to ensure continuity during power failures.
Prime power ratings are used for generators that must provide power for long periods with varying loads. Unlike standby power, prime power is meant for continuous use in locations without a reliable grid.
While standby power is for backup during emergencies, prime power is used for more extended operations. Prime power generators can handle continuous, varying loads and can run for as long as needed, though with certain limitations.
Rating | Use Case | Power Handling |
Standby Power | Short-term backup | Can’t handle continuous use |
Prime Power | Continuous, varying loads | Designed for long-term use |
Prime power allows for up to 10% overload for up to one hour within a 12-hour cycle. However, running a generator at full load for long periods can cause wear and tear, reducing its lifespan.
Continuous power refers to a generator’s ability to run at full load without interruption for an unlimited amount of time. These generators are designed to operate non-stop, providing consistent power to critical equipment.
Certain applications, like military bases, mining operations, and large-scale industrial facilities, require continuous power to operate. These generators ensure there’s no power interruption, which is vital for these sectors.
Running a generator continuously at full load can be challenging. While it's possible, it’s essential to maintain proper maintenance and ensure the generator is rated for continuous full-load use. These generators must be regularly serviced to avoid overheating and damage.
Limited time power ratings are designed for generators that can run for a set number of hours per year, typically up to 500 hours. These generators are ideal for temporary use, such as during planned utility maintenance or short-term power needs.
Limited time power generators are best for situations where the generator will only be used occasionally. If you know your power needs will be temporary, such as during construction projects or seasonal use, these generators are a cost-effective option.
Understanding key factors like load factor and power factor is essential to choosing the right generator. These factors help ensure your generator operates efficiently and provides enough power for your needs.
Load factor refers to the ratio of the actual electrical load the generator is using compared to its maximum capacity. A higher load factor means the generator is being used efficiently, while a low load factor indicates underuse.
The load factor directly impacts how efficiently a generator uses fuel and generates power. If a generator is consistently running at low loads, it’s not operating efficiently, and energy is wasted.
To calculate load factor, use this formula:
Load Factor = (Average Load) / (Maximum Capacity)
For example:
● If your generator runs at an average load of 500 kW, and its maximum capacity is 1,000 kW, then:
Load Factor = 500 kW / 1,000 kW = 0.5
This means the generator is only operating at 50% of its full potential. A higher load factor would indicate more efficient use of the generator's capacity.
Load Factor | Efficiency | Usage |
0.5 | Low Efficiency | Wasting energy |
0.9 | High Efficiency | Optimized power usage |
Power factor is a measure of how efficiently a generator converts electrical power. It compares the real power used by equipment to the total power provided by the generator, which includes both real and reactive power. A higher power factor indicates more efficient use of electrical power.
The power factor is calculated based on the devices connected to the generator, as reactive power affects how much energy is wasted in the system.
The formula for calculating power factor is:
Power Factor = Real Power (kW) / Apparent Power (kVA)
For example:
● If the generator is supplying 800 kW of real power and 1,000 kVA of apparent power, the power factor is:
Power Factor = 800 kW / 1,000 kVA = 0.8
A power factor of 0.8 is typical for most generators. A lower power factor indicates inefficiency, while a power factor closer to 1.0 means the generator is using its power efficiently.
Apparent Power kVA | Real Power kW | Power Factor |
1,000 kVA | 800 kW | 0.8 |
1,500 kVA | 1,400 kW | 0.93 |
A higher power factor means more of the generator's total power is being converted into usable electrical power. This leads to better fuel efficiency, lower operating costs, and a longer lifespan for the generator. A generator with a high power factor will operate more smoothly, with less waste, and at a lower cost.
Choosing the right generator isn’t just about picking the most powerful option. You need to consider factors like load capacity, the size of your space, and specific power needs. Let’s go over some key steps to help you make the right choice.
Knowing the full load capacity of your generator is crucial. It ensures your generator can handle peak power demands without overloading. If a generator is too small, it might struggle during high-demand times, risking failure or damage. If it’s too large, you may waste fuel and increase operational costs.
Here’s a simple guide to help you calculate the full load capacity:
1. Measure the total current load:
Look at the total power usage of your equipment when everything is running at full capacity. You can measure this with ammeters on each leg of the electrical system.
2. Convert current to kilowatts:
After obtaining the total amps used, convert this to kilowatts (kW).
Use the formula:
kW = Amps × Voltage / 1,000
3. Determine the generator size:
To ensure a proper match, consider using 1.2 times the full load kW to account for starting surges.
Measurement | Steps | Formula |
Total Current | Measure total amps used | - |
Conversion | Convert to kilowatts kW | kW = Amps × Voltage / 1,000 |
Generator Size | Add surge factor | Generator Size = 1.2 × kW |
Calculating the full load capacity ensures your generator can handle the highest demand without overloading.
Square footage helps estimate the required power for small businesses or retail stores. A larger space usually needs more power, especially if there are many appliances or machines running.
Here’s a simple method to estimate generator size based on your space:
● Retail spaces: Start with a 50 kW generator, then add 10 kW for every 1,000 square feet.
● Commercial spaces: Start with 50 kW, then add 5 kW for each 1,000 square feet.
For example:
● A 2,000 sq. ft. retail store would need:
50 kW + (10 kW × 2) = 70 kW
● A 2,000 sq. ft. office would need:
50 kW + (5 kW × 2) = 60 kW
Type of Space | Base Power | Power per 1,000 sq. ft. | Total Power for2,000sq.ft. |
Retail Store | 50 kW | 10 kW | 70 kW |
Commercial Office | 50 kW | 5 kW | 60 kW |
Residential generators typically require a power rating between 5 kW to 20 kW, depending on the size of the home and the number of devices you need to run. Common appliances like refrigerators, air conditioners, and lighting need to be considered.
For small businesses or offices, a generator power rating of around 20 kW to 50 kW is usually enough. The generator should be able to power essential equipment, like computers, lights, and small appliances.
Industrial generators often require power ratings between 100 kW to several MW, depending on the size of the facility and the equipment. These generators are designed to handle large machinery, complex systems, and heavy loads without interruption.
Application | Typical Power Rating | Use Case |
Residential | 5 kW to 20 kW | Powers home appliances and lights |
Commercial | 20 kW to 50 kW | Powers office equipment, lights |
Industrial | 100 kW to several MW | Powers large machinery, factories |
The performance of a generator is directly influenced by its power ratings. Understanding how factors like altitude, temperature, and proper sizing affect its efficiency can help you maximize the generator's lifespan and reduce operational costs.
At higher altitudes, the air is thinner, which means less oxygen is available for combustion. This can reduce a generator’s power output. To account for this, generators may need to be derated (reduce power output) when operating at high altitudes.
For example:
● At 2,000 feet, a generator may need a 3% reduction in output.
● At 5,000 feet, it could be reduced by 10%.
This derating ensures the generator continues to run efficiently despite the lower oxygen levels.
Altitude | Power Loss | Effect on Generator |
2,000 ft | 3% | Slight reduction in output |
5,000 ft | 10% | Significant power reduction |
Temperature has a similar effect on generator performance. High temperatures cause engines to overheat, leading to lower efficiency and possible damage. To prevent overheating, generators may also need to be derated in hot climates.
● For every 10°F above 100°F, generator power may drop by 1%.
● Extreme heat increases the likelihood of engine wear, making it harder for the generator to reach its full power potential.
Understanding the temperature in which your generator will operate helps ensure that it’s correctly sized and ready for challenging conditions.
Temperature | Power Loss | Effect on Generator |
100°F | 0% | No impact |
110°F | 1% | Slight reduction in output |
120°F | 2% | Increased power loss |
Using a generator with the correct power rating ensures it operates at its optimal efficiency. A generator that’s too small will constantly run at full load, consuming more fuel and shortening its lifespan. Conversely, a generator that’s too large will waste energy and money, running inefficiently at lower loads.
By choosing the right generator, you can reduce fuel consumption, lower operating costs, and decrease emissions.
Generators that are properly sized for the load they need to support will experience less stress. This reduces wear and tear on the engine and components, ultimately extending the lifespan of the unit. Running a generator at or near its full capacity consistently can cause faster degradation, leading to costly repairs and maintenance.
Generator Size | Efficiency | Lifespan Impact |
Properly Sized | Optimal | Longer lifespan, less wear |
Undersized | Low | Frequent breakdowns, short lifespan |
Oversized | Wasteful | Energy waste, higher costs |
A: kW (kilowatts) represents usable power, while kVA (kilovolt-amperes) includes both real and reactive power. kVA measures the total power a generator can produce, but only the real power (kW) is used by equipment.
A: Choose a generator with a power rating that matches your equipment's peak load. Consider both continuous and surge power needs, and use kW for real power and kVA for overall capacity.
A: Overloading a generator can cause overheating, damage to the engine, and potentially shorten its lifespan. It can also lead to power interruptions and system failure.
A: You cannot change the generator’s inherent power rating, but you can adjust its operation by adding external equipment or using it at different load levels to match the needs of your application.
A: The power factor is the ratio of real power (kW) to apparent power (kVA). It indicates how efficiently the generator converts electrical power. A higher power factor means better energy efficiency and reduced operational costs.
Understanding generator power ratings is essential for choosing the right generator. eKW, kVA, load factor, and power factor all impact performance and efficiency.
When selecting a generator, match the power rating to your equipment's needs. Consider factors like load capacity, altitude, and temperature. Proper sizing ensures optimal performance, reduces energy waste, and extends the generator's lifespan. Use the information here to make an informed, cost-effective choice for your power needs.
