What size inverter do I need for a work truck?

Determining the right size inverter for a work truck depends on several factors. The main considerations are:

• Power requirements – How much power will you need to run the tools, equipment, and accessories in your truck?
• Inverter type – Will a modified sine wave or pure sine wave inverter work better for your needs?
• Peak power rating – How much instantaneous power do your devices require for starting up?
• Continuous power rating – How much constant power do your devices require?
• Battery size – What is the voltage and amp hour rating of your truck’s battery or battery bank?

In this article, we’ll discuss these key factors and considerations for selecting the optimal inverter wattage for a work truck.

Determine Your Power Requirements

The first step is to make a list of all the electrical devices and tools you need to operate in your truck. This should include:

• Power tools – drills, saws, sanders, grinders, etc.
• Job site electronics – laptops, tablets, printers, monitors, etc.
• Office electronics – computer, printer, lighting, mini-fridge, etc.
• Safety equipment – radios, back up cameras, charging for safety vests, etc.
• Appliances – microwave, coffee maker, televisions, etc.
• Phone and device charging

Once you have your list, determine the wattage for each device. The wattage should be listed in the manual or on a label on the device.

For devices that don’t list wattage, here are some common estimates:

Device	Watts
Laptop	50-100
Compact fluorescent light	7-13
Radio	5
Electric cooler (16 quart)	75
Window AC unit (8000 BTU)	600-1000
Microwave	750-1100
Coffee maker	600-1200

Add up the wattages of all the devices you need to run simultaneously to determine your total wattage requirement. It’s important to consider the maximum number of devices that could potentially be running at the same time.

Understand Peak Power vs. Continuous Power

When sizing an inverter, it’s important to understand peak power versus continuous power:

• Peak power is the maximum wattage an inverter can supply for a short time, usually for 10 seconds or less. This peak power rating is important for handling surge wattage that happens when a device starts up. The peak power is always higher than the continuous rating.
• Continuous power is the wattage an inverter can supply constantly over an extended period of time. This is typically around 90% of the peak power rating.

For example, a 1000W inverter may provide a peak of 1000W but only a continuous output of around 900W.

To figure out the right size inverter, you need to look at both the continuous and peak power demands of your work truck devices.

Factor in Power Losses

When calculating your power needs, it’s important to factor in losses that will occur. You should increase your total wattage requirement by 20% to account for things like:

• AC-to-DC inversion losses – Power lost converting DC from batteries to AC
• Wire losses – Power dissipated as current flows through wires
• Charging losses – Power used to recharge batteries
• Aging – Losses due to dusty or corroded electrical connections

If your device total is 1000W, multiply it by 1.2 to get a required wattage of 1200W. The extra overhead will ensure your inverter isn’t running at full capacity and overheating.

Use a Sizing Factor for Motors and Pumps

Devices with electric motors and pumps often require surge wattages 3-5x their rated wattage when starting up.

Here is a table showing common sizing factors:

Device Type	Sizing Factor
Small fan, blender	2-3x rated watts
Refrigerator compressor	3-4x rated watts
Air conditioner, large compressor	4-5x rated watts
Submersible well pump	5x rated watts

To calculate the surge wattage, multiply the device’s rated wattage by the sizing factor. For example, a 500W submersible pump would need 500 x 5 = 2500W surge capacity from the inverter.

Select a Pure Sine Wave or Modifed Sine Wave Inverter

Inverters come in two main types:

• Pure sine wave: Produces clean AC power like you get from an electrical outlet at home. Recommended for sensitive electronics and motors.
• Modified sine wave: Affordable but outputs rougher power that may damage sensitive equipment over time. Only recommended for simple resistive loads like lights and basic charging.

For a work truck running power tools, radios, laptops, and other electronics – a pure sine wave inverter is highly recommended. The clean power output will prevent damage to equipment and avoid malfunctions.

Though more expensive, pure sine wave inverters are worth the investment for a work truck with valuable gear on board.

Understand Inverter Capacity Relative to Battery Capacity

When sizing an inverter, it’s important to consider the capacity of your battery bank and how long you need to run devices between charges.

A common guideline is to size your inverter wattage to around 10-25% of your total battery bank capacity (in watt-hours).

For example:

• 200Ah 12V battery = 2400W battery capacity
• 10% of 2400W is 240W
• 25% of 2400W is 600W

So with this 200Ah 12V battery, an inverter size between 240W – 600W would be suitable, depending on your runtime requirements.

A smaller inverter draws less current from the batteries – extending your runtime. A larger inverter can draw more current – providing more power but decreasing runtime between charges.

Leave Room for Future Expansion

When deciding on an inverter size, it’s a good idea to add an extra 20-30% capacity to allow for future expansion.

Your power needs may grow over time if you add more equipment and electronics to your truck. Having extra overhead with your inverter prevents having to replace it prematurely when your load increases.

Use Multiple Smaller Inverters for Separate Circuits

Rather than using one large inverter for your entire truck, consider using multiple smaller inverters for separate electrical loads and circuits.

For example, you could use:

• 500W inverter for charging phones/laptops
• 1000W inverter for a microwave and mini-fridge
• 2000W inverter for power tools and a cooling fan

This modular approach allows you to tailor inverter sizes more closely to the loads they power. You can turn off inverters for unused circuits to conserve energy. And if one fails, you still have power to other essentials.

Installing multiple smaller inverters provides more flexibility than a single large unit. Just be sure to get pure sine wave inverters rated for RVs or off-grid use.

Select an Inverter with the Right Outlets

Ensure the inverter you choose has the appropriate type of AC outlets you need. For a truck, common options are:

• Standard 2-prong 120V household outlets
• 3-prong 120V outlets with ground connection
• USB charging ports
• Cigarette lighter 12V DC outlet

The inverter should have enough outlets to plug in all your required devices without constantly needing to unplug and switch cords.

Specialized RV inverters will also have useful features like overload protection, scrolling digital displays, and rugged outer casings.

Placement and Ventilation

When installing your inverter, choose a place with good ventilation to prevent overheating. The inverter should be out of direct sunlight and away from engine heat.

Inverters produce a lot of wasted heat energy during the AC conversion process. Allow at least 2 inches of clearance around the inverter for air flow. Active cooling fans are also highly recommended for larger inverters.

Proper placement and ventilation will enable your inverter to run more efficiently and extend its lifespan.

Conclusion

Choosing the right size inverter for a work truck involves:

• Calculating your total wattage needs
• Accounting for surge capacity and power losses
• Comparing battery capacity and runtime
• Selecting pure sine wave for robust power
• Allowing room for future expansion
• Using multiple smaller inverters for flexibility

Taking the time to properly size your inverter will ensure reliable off-grid power for all your truck’s work tools and electronics. A pure sine wave inverter sized at 10-25% of your battery capacity is usually optimal for most setups.

Install your inverter in a well-ventilated position and use adequately sized wiring to supply ample clean power from the batteries to your AC loads. With some thoughtful planning, you can work confidently from your truck using grid-independent inverter power.

Frequently Asked Questions

What size inverter do I need to run power tools in my truck?

To run power tools like drills, sanders, and saws, you will likely need at least a 1000W-2000W pure sine wave inverter. The power needs can vary greatly though, so check your tool manuals for wattage ratings and add up the maximum that could run simultaneously. Multiply motors and compressors by 3-5x rated watts.

What size inverter for a truck fridge?

A 12V truck fridge often pulls 50-100 watts. A 120V AC compact fridge or cooler can draw 100-400 watts. Use an inverter sized at least twice the fridge power – so look for a 200W+ pure sine wave unit for reliability.

Can I use a cheap modified sine wave inverter in my truck?

It’s not recommended. The poor waveform of modified sine wave inverters can damage motors in power tools over time and cause glitches in sensitive electronics. Spend a little more upfront for a pure sine inverter with surge protection for clean reliable power.

Where is the best place to install an inverter in a truck?

Install your inverter in a protected interior location like under the back seat or a side cabinet. Choose an area away from engine heat and with good ventilation. Make sure you can securely mount the inverter and easily access the outlets and controls.

How do I know if my truck alternator is powerful enough?

Check your alternator amperage rating. At idle it provides around 40% of its rated output; at cruising speed around 90%. With dual batteries, a 140-160A alternator is usually sufficient for running a 1000W inverter and recharging. Higher electrical loads may require upgrading to a larger 240A alternator.

Can I use a power inverter while driving?

Yes, you can safely run an inverter when driving to power electronics and charge devices. Just check the inverter manuals and ensure the truck battery receives sufficient recharging from the alternator. Avoid drawing more power than the charging system can handle.

Conclusion

Choosing the optimal inverter for a truck involves balancing your power needs, battery capacity, and electrical system capabilities. While it may take some calculations and electrical understanding, the investment of a properly sized pure sine wave inverter will provide reliable off-grid power for all your work and recreational needs on the road.