Which Portable Power System to Choose?

Choosing the right size for a portable power system doesn’t have to be tricky. Imagine the confidence of knowing exactly how much power you need—whether you’re camping, in your RV, or readying for a power outage at home. Which portable power system to choose? Well, here’s a simple guide to show you how to size a portable power system for your needs.

Having the right-sized power system can make all the difference between a smooth experience and scrambling for power. So, let’s break it down!

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Step 1: List Your Devices and Their Power Needs

Start by listing all the devices you plan to power. For example, on a 3-day camping trip, your list might include phones, laptops, lights, and a mini-fridge. Your list will vary depending on your setup.

Each device has a power rating in watts (W), which is often on the label, charger, or manual. Here’s an example of common items:

• Phone charger: ~10W
• Laptop: ~50W
• LED light: ~5W
• Mini fridge: ~60W

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Step 2: Estimate Your Daily Usage

Now, estimate how many hours you’ll use each device per day. Multiply the wattage by the hours to get the daily watt-hours (Wh) each device will need.

Example for charging a phone:

• 10W phone charger × 3 hours = 30Wh per day

Repeat for each device, then add up the watt-hours for your total daily power need.

Example Daily Calculation:

• Phone charger: 10W x 3 hours = 30 Wh
• Laptop: 50W x 4 hours = 200 Wh
• LED light: 5W x 4 hours = 20 Wh
• Mini fridge: 60W x 24 hours = 1,440 Wh
  Total Daily Wh: 30 + 200 + 20 + 1,440 = 1,690 Wh

For simplicity, you can round this up to 1,700Wh per day.

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Step 3: Multiply by the Number of Days

Now, multiply your daily total by the number of days you’ll be off the grid or without power. For a 3-day trip:

• 1,700 Wh per day × 3 days = 5,100 Wh

This means you’ll need at least 5,100 Wh for the full trip. But we’re not done yet—there are a few more adjustments to make sure you’re fully covered. To be precise, you can go to Step 4 or to get in the neighborhood of your needs, multiply the 5,100W by 1.4 to get 7140W. That will get you close to your final number.

Ballpark Power Needs

5,100W x 1.4 = 7140W

You could stop here and be close with a little margin for your needs. If that’s good enough for you, great! This will power your devices with a little bit of margin, so you won’t run out of power.

But if you like me, I want to know more, which takes you to Step 4.

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Step 4: Adjust for Voltage Differences and Inverter Losses

Some devices, like laptops and AC-powered appliances, need more power to run on a portable power station. This is because the power station has to convert DC power to AC power. Typically, there is a 7% to 15% loss of power for this process. Here’s how to adjust for this loss:

Laptop Power Adjustment

Most laptops use 18-20V DC, while most power stations output 12V or 120V. To account for the voltage difference, multiply your laptop’s watt-hours by 1.2. Here’s an example:

• 50W × 4 hours × 3 days = 600 Wh → 600 Wh x 1.2 = 720 Wh

Inverter Loss for AC Devices

Converting DC to AC (like for a mini-fridge) usually causes a 15-25% energy loss. Multiply by 1.25 to account for this. The mini fridge uses high power and may cause a higher loss depending on the power station.

For example, the mini-fridge:

• 60W × 24 hours × 3 days = 4,320 Wh → 4,320 Wh x 1.25 = 5,400 Wh

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Step 5: Add a 20-30% Buffer for Assurance

Lastly, add a 20-30% buffer to your total watt-hours for extra assurance. This buffer covers unexpected device needs or efficiency losses. For example, if your adjusted total is 6,120 Wh, add a 25% buffer:

• 6,120 Wh × 1.25 = 7,650 Wh

This final number represents the ideal total watt-hours your portable power system should have to cover your needs comfortably. Your choice doesn’t have to be exactly the calculated number, but it should be close to ensure you have plenty of power.

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Quick Summary Table of Example Calulations

Device	Daily Wh	Adjusted Wh (3 days)
Phone Charger	30 Wh	90 Wh
Laptop	200 Wh	720 Wh
LED Light	20 Wh	60 Wh
Mini Fridge (adjusted)	1,440 Wh	5,400 Wh
Total for 3 Days		6,270 Wh
With Buffer		7,650 Wh

This is an example of how to size a portable power station or system. You can do it in several ways, but the point is to know what devices you might use, their watts, and how long you might use them. You can use the loss factor or just double your overall power system. But some amount of overestimating will only ensure your adventure goes smoothly.

In emergency situations, remember it may not just be your devices as others around you will also be in need. So having a good-sized portable power system and a solar panel to recharge will give you peace of mind and ensure you can help yourself and others if nature causes problems.

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Ready to Get Powered Up?

Sizing your portable power system comes down to estimating your daily needs, adjusting for voltage and inverter efficiency, and adding a buffer. With these steps, you’ll have the perfect power setup for camping, RVing, emergencies, or any adventure life throws at you!

A solar panel is a great way to stretch the power you have and ensure you are ready to go for the evening and the next day. But also, adding the buffer and just having a little extra power is peace of mind when camping or in emergency situations.

If your interest is peaked, the absolute source for many engineers or DIY homeowners is Ugly’s Electrical References, which is the gold standard on-the-job reference tool of choice for electrical industry professionals.

Reference:

The Engineering Toolbox. https://www.engineeringtoolbox.com/electrical-formulas-d_455.html

Ugly’s Electrical References, 2023 Edition