Do you have a 2.5 horsepower (HP) compressor that you want to use for various purposes, such as inflating tires, powering pneumatic tools, or spraying paint?
If so, you might be wondering what size generator you need to run it smoothly and safely. In this blog post,
We will explain how to choose the right generator size for your 2.5HP compressor, and what factors you should consider before making your purchase.
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What Size Generator To Run a 2.5HP Compressor?
To run a 2.5HP compressor, you typically need a generator with at least 6250 starting watts. It ensures efficient and uninterrupted operation of the compressor by handling the initial surge in power demand.
Generator sizes chart to run a 2.5HP compressor:
Generator Size (Watts) | Generator Type | Power Output (Volts/Amps) |
|---|---|---|
| 5000 | Inverter | 120/240V, 20/41.7A |
| 5500 | Portable | 120/240V, 22/45.8A |
| 6000 | Standby | 120/240V, 25/50A |
| 6500 | Diesel | 120/240V, 27/54A |
Different Types of Generators Compatible with a 2.5HP Compressor
Inverter Generators
Inverter generators are generators that use advanced technology to produce clean and stable power that is similar to the electricity from the grid.
They are usually smaller, lighter, quieter, and more fuel-efficient than other types of generators.
They are also safer for sensitive electronics, such as laptops, phones, or TVs.
Portable Generators
Portable generators are generators that are designed to be moved around easily from one place to another.
They are usually powered by gasoline or propane and have wheels and handles for easy transportation.
They are also cheaper and more powerful than inverter generators.
Standby Generators
Standby generators are generators that are permanently installed in your home or business and connected to your electrical panel.
They automatically turn on when there is a power outage and provide continuous power to your essential appliances and devices.
They are usually powered by natural gas or propane and have large fuel tanks and capacity.
Diesel Generators
Diesel generators are generators that use diesel fuel as their main source of power.
They are usually more durable and reliable than other types of generators, and they have longer run times and lower fuel costs.
They are also less likely to catch fire or explode than gasoline or propane generators.
Calculating the Required Generator Size for a 2.5HP Compressor
Here is a step-by-step guide on how to calculate exactly the generator size you need for your specific situation.
The Power Needs of a 2.5HP Compressor
The starting watts are the peak power that your compressor needs to start up, which is usually several times higher than the running watts.
The running watts are the average power that your compressor needs to operate continuously, which is usually much lower than the starting watts.
You can find these numbers in the manual or on the label of your compressor, or you can use this formula to estimate them:
Starting Watts = Horsepower x 2000
Running Watts = Horsepower x 750
For example, if your compressor has a horsepower of 2.5, you can calculate the starting and running watts as follows:
Starting Watts = 2.5 x 2000 = 5000
Running Watts = 2.5 x 750 = 1875
This means that your compressor needs about 5000 watts to start up and about 1875 watts to run continuously.
Conversion of Horsepower to Watts
Your compressor is measured in horsepower (HP) but your generator is measured in watts (W).
This is because horsepower is a unit of mechanical power, while watts is a unit of electrical power.
To convert horsepower to watts, you need to multiply by a factor of 746, which is the amount of electrical power equivalent to one mechanical horsepower.
For example, if your compressor has a horsepower of 2.5, you can convert it to watts as follows:
Watts = Horsepower x 746
Watts = 2.5 x 746 = 1865
This means that your compressor has an electrical power of about 1865 watts.
This conversion is not exact, because it does not account for the efficiency loss that occurs when converting mechanical power to electrical power.
The efficiency loss is the amount of power that is wasted or lost during the conversion process, which is usually between 10% and 20%.
To account for the efficiency loss, you need to divide by a factor of 0.8, which is the average efficiency rate of most compressors.
For example, if your compressor has an electrical power of 1865 watts, you can adjust it for efficiency loss as follows:
Adjusted Watts = Watts / 0.8
Adjusted Watts = 1865 / 0.8 = 2331
This means that your compressor actually needs about 2331 watts of electrical power to operate at its full capacity.
Calculating Starting and Running Watts
The starting watts are still calculated by multiplying the horsepower by 2000, but then you need to divide by 0.8 to account for efficiency loss.
For example, if your compressor has a horsepower of 2.5, you can calculate the starting watts as follows:
Starting Watts = (Horsepower x 2000) / 0.8
Starting Watts = (2.5 x 2000) / 0.8 = 6250
This means that your compressor needs about 6250 watts to start up.
The running watts are calculated by multiplying the adjusted watts by a factor of 0.8, which is the average load factor of most compressors.
The load factor is the ratio of the actual power used by your compressor to its maximum possible power output.
It is usually between 60% and 100%, depending on how hard your compressor is working.
For example, if your compressor has an adjusted wattage of 2331 watts, you can calculate the running watts as follows:
Running Watts = Adjusted Watts x Load Factor
**Running Watts = 2331 x 0.8 = 1864
This means that your compressor needs about 1864 watts to run continuously.
Considering Additional Appliances or Tools
So far, we have only calculated the power needs of your compressor alone, but you may also want to run other appliances or tools along with your compressor, such as lights, fans, drills, saws, or heaters.
If so, you need to add the starting and running watts of all the appliances or tools you want to run simultaneously to the starting and running watts of your compressor.
For example, if you want to run a 100-watt light bulb, a 200-watt fan, and a 600-watt drill along with your 2.5HP compressor, you need to add their starting and running watts as follows:
Total Starting Watts = Starting Watts of Compressor + Starting Watts of Other Appliances or Tools
Total Starting Watts = 6250 + 100 + 200 + 600 = 7150
Total Running Watts = Running Watts of Compressor + Running Watts of Other Appliances or Tools
Total Running Watts = 1864 + 100 + 200 + 600 = 2764
This means that you need a generator that can provide at least 7150 watts of starting power and at least 2764 watts of running power to run your compressor and other appliances or tools at the same time.
Factoring in Efficiency Loss
Efficiency loss is the amount of power that is wasted or lost during the generation and transmission of electricity.
It is usually between 10% and 20%, depending on the quality and condition of your generator and wiring.
To factor in efficiency loss, you need to multiply the total starting and running watts by a factor of 1.1, which is the average efficiency loss rate of most generators.
For example, if your total starting and running watts are 7150 and 2764, respectively, you can factor in efficiency loss as follows:
Adjusted Total Starting Watts = Total Starting Watts x Efficiency Loss Factor
**Adjusted Total Starting Watts = 7150 x 1.1 = 7865
Adjusted Total Running Watts = Total Running Watts x Efficiency Loss Factor
**Adjusted Total Running Watts = 2764 x 1.1 = 3040
This means that you need a generator that can provide at least 7865 watts of starting power and at least 3040 watts of running power to run your compressor and other appliances or tools at the same time with minimal efficiency loss.
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Benefits of using an overpowered generator for 2.5 hp air compressor
Throughout the guide, we have suggested using an overpowered generator to run an air compressor. Let’s have a look at the reason behind it:
It is safe
The calculation may not be 100% correct and if the wattage of the generator doesn’t exceed the requirement, it will cause plenty of difficulties.
So the compressor may not run and it may put excess pressure on the generator, resulting in reduced longevity.
Versatility
A more powerful generator is needed to run multiple appliances at a time and even run a single larger machine like a 2.5 HP compressor.
The life span of the generator
Running a generator consistently at maximum power puts extra pressure on it, which can reduce its life span.
While using the less powerful generator will encourage you to set the output levels at maximum speed.
Using the overpowered generator will allow you to keep the output level low.
Apart from this, you shouldn’t run a generator at maximum output consistently for over 30 minutes.
Best Generator For 2.5HP Compressor
1. Champion Power Equipment 9375/7500-Watt Portable Generator
- Ultra-Powerful: At 9375 starting watts and 7500 running watts, enjoy up to 8 hours of run time on a full tank of gasoline with a noise level of 74 dBA from 23 feet
- Electric start: Trust the reliable 420cc Champion engine with its battery-included electric start featuring a reliable toggle switch, plus built-in Cold Start Technology for easy starts in cold weather
- Covered Outlets: Four 120V 20A GFCI outlets, a120/240V 30A locking outlet and a 120/240V 50A outlet (14-50R), plus Volt Guard built-in surge protector prevents overloads and keeps your equipment safe
- Intelligauge: Keep track of voltage, hertz and run-time hours to easily monitor power output and track maintenance intervals
- Champion Support: Includes 3-year limited warranty with FREE lifetime technical support from dedicated experts
2. Westinghouse Outdoor Power Equipment WGen7500 Portable Generator
- 7500 Running Watts and 9500 Peak Watts; Remote Start With Included Key Fob, Electric and Recoil Start; Up to 11 Hours of Run Time on a 6.6 Gallon Fuel Tank With Fuel Gauge
- Features Two GFCI (Ground Fault Circuit Interrupter) 5-20R 120V Household Duplex Receptacle and One L14-30R 120/240V Twist-Lock Receptacle; All Outlets Have Rubber Covers for Added Safety
- Plug-and-Play: Comes with a Remote Start Key Fob, 12V Battery Charger, Oil, an Oil Funnel, a Tool Kit, and a User’s Manual to Get You Started Right Out of the Box (Minimal Assembly Required)
- Powered by a 420cc Westinghouse 4-Stroke OHV Engine Featuring a Long-Lasting Cast Iron Sleeve with Automatic Low Oil Shutdown and Digital Hour Meter. Output Ready Indicator : No.
- All Westinghouse Portable Generators are Functionally Tested in the Factory and May Contain Minimum Residual Oil and/or Fuel Odor; EPA and CARB Compliant; Backed by 3-Year Limited Service, Labor, and Parts Coverage with Nationwide Customer Service Network
3. A-iPower SUA12000E 12000 Watt Heavy Duty Gas Powered Generator
- The A-iPower SUA12000 produces 12,000 starting watts with 9,000 running watts to power your tools at the construction site, camping ground, or home appliances
- Powerful 459 cc OHV 4 stroke engine with a low oil alert light and low oil automatic shutdown, helping keep your generator performing year after year
- Large 7 gallon gasoline fuel tank provides average run time of 7 hours at 100% load and 9 hours at 50% load
- Complete with Electric Start capability allowing you to quickly, easily, and conveniently start up your generator whenever you need it
- Outlets include 4 x GFCI 120V 20A NEMA5-20R, 1 x 120V 30A NEMAL 5-30R, 1 x 120/240V 30A NEMA L-14-30R, 1 x 12V83A Multifunction Port USB Ready All outlets include Rubber Covers for an additional layer of Safety
FAQs About Right Size Generator For 2.5 HP Compressor
How Many Watts Does An Air Compressor Need?
A 110-volt air compressor that draws 15 amps requires 1,650 watts to keep running efficiently. If the air compressor is 220 volts and draws 15 amps, it will require 3,300 watts.
Why Should I Use A Generator To Run A Compressor?
Some people use generators as a temporary power source during an electric power outage while some run appliances that require more power than the electrical system.
What Is The Best Generator For A 2.5HP Compressor?
The DuroMax XP8500EH Dual Fuel Portable Generator will be the best generator to run a 2.5 HP compressor.
Final words
Whether you have a home garage or need to inflate a sprinkler or tire, an air compressor is a must-have device.
Above it, the right-sized generator can let you operate the compressor consistently without the worry of a power outage.
Throughout the guide, we have discussed what size generator to run a 2.5 HP compressor and how to determine it.
Hopefully, you have got the idea and are prepared to get the right one.
