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Calculating How Much Electricity You Need To Live In A Van

We are living in an era of electronics. With the ease of working online, and the demand of powered entertainment, electricity is a common concern among van builders. Figuring out how to get enough electricity in the van to power all of your needs can be one of the most overwhelming parts of a van build.

With so many different opinions, it can be daunting trying to figure out how to best tackle electricity; especially for someone with no prior experience. Fortunately, you don’t need to learn everything in order to gain the benefits of electricity.

The goal of this post is to break down how to calculate how much energy you need. With this information, you will know how much power to collect and store in secondary batteries.

Checklist of Electronic Devices
This checklist will help decide what to pack

 

How much power do you want?

It’s easy to think that for the most comfortable vanlife experience, you need to collect and store as much power as possible. However, before you start making slow-cooker and air-conditioner plans, a good question to ask is “why haven’t I ever seen these things in other van builds?” It is usually because the electrical power draw is incredible, the setup would be large or expensive, or there is an easy workaround. Perhaps the correct answer is – all of the above!

Like anything in a van build, there is no right way to do electricity. In fact, electricity may not even be a necessity. For every piece of electrical equipment, a good thought experiment is to figure out how you would comfortably deal without it. This process of experimentation should help you determine what you need and what you want.

If you have the time, as we recommend elsewhere, it is even better if you can physically take the van out and try living for a weekend with no electricity to see what you miss the most. Some things you quickly find that you really appreciate (for us it’s a fridge) and others you don’t miss at all (for us that would be a sink pump). 

Everyone will be different in this aspect. Some people do indeed end up installing a microwave. Some just use an ice box and portable solar charger for their cell phone. If something like cooking is a main goal many people build elaborate kitchens that function quite well. In the end, there will be more hand chopping of veggies than using a food processor, but vanlife doesn’t have to feel like living in a metal tent.

Common electric items you might be able to live without

Electric Stove: There are a plethora of propane, butane, and wood stove options. Some people eat cold food and at restaurants.

Microwave: Most things heated in a microwave can be heated by, if not improved upon, by using a stove. Most of the things we re-heat on a skillet are far better than they would be in a microwave.

Refrigerator: A cooler re-filled with ice is a pretty good refrigerator imitator. Most food can go a day or two without refrigeration depending on the outside temp.

Computer: In cities, towns, and public places there are outlets everywhere. You can work at McDonalds for an hour or two charging your computer and have enough battery to work later as well. For less than a $2 coffee you could do this every other day and you just saved yourself $800 in a solar setup. You can even buy external or even integrated replacement batteries for your device to charge.

Air-Conditioner: Make use of ventilation techniques to keep airflow throughout the van. Move to colder locations during the summer. Park your van in the shade during the day.

Lighting: Modern LED lights will go for days on a single replaceable battery so lights are not too difficult to accommodate.

Electric Heater: Like the stove, there are fuel-based options as well as having a well-designed insulation system. Utilizing your body heat with sleeping bags and blankets reduces the need for this.

Electric water pump: There are hand and foot pump options for a van build that many people use instead. Others forgo the sink and wash dishes outside.

No coffee maker:  There are many efficient water-heating systems that you can make pour-over or French press coffee with.

This isn’t meant to dissuade you from choosing to use any of the above items. It is to get you thinking about how valuable the resource is before running some numbers and going out to buy expensive electrical devices.

How To Calculate Energy Needs

The first step to powering your van is to get a good estimate of how much power you need. Make a list of all the electric devices you plan to power on the road. Use this checklist of common electrical devices to help you along. Be sure to add anything we’ve missed. Next, we’re going to walk-though how to calculate the power draw for each item.

Alternating Current (AC) vs Direct Current (DC) Power

When looking up that stats on your electronic devices, you’ll notice that some items are measured in amps, some items are measured in watts, and some are entirely different! What does this mean?

There are two different types of power at play, one is called direct current (DC) power and one is called alternating current (AC) power.

Direct Current (DC) Power

Direct current refers to a type of power that flows in one direction. Most digital electronics such as your cell phone use direct current power. Anything you plug into a cigarette lighter or USB cable is run off DC power. Batteries function using direct current power which is the main reason it is used in vehicles.

Alternating Current (AC) Power

Alternating current power is a different type of electricity where the flow is consistently changing directions. Houses and office buildings use AC power. The main reason is because it is more efficient to transmit AC over long distances. Our electrical grid uses AC power to deliver electricity to buildings. Due to this, US household appliances are all designed to be plugged into AC outlets.

Categorizing your list of electronics

Go through your list of electronics and determine which items run off DC power, and which items run off AC power. Because the energy you collect through either solar panels, a generator, or electric hookup will be stored in batteries, the electricity you receive from those batteries will come in the form of DC power.

Any AC powered item you run off battery power will require an inverter. To put it simply, an inverter turns DC power into AC power. During this transformation process, there will be a small loss of energy.

To get the biggest bang for your buck, you want to minimize the number of AC powered items in the van, and maximize the number of DC powered items.

The most common items on your list, such as a refrigerator, can usually be bought as either AC powered or DC powered. The mini-fridge on sale at Walmart during the start of the school year is an AC powered item (it plugs directly into a household socket). However, if you purchase an RV fridge or a boat refrigerator you will be bringing home a DC powered item. This is because boats and RV’s run off batteries, and have the accessories to match! Search marine or RV stores to find DC electronics. Travelers have been finding alternatives to their AC devices for a long time, so chances are you will find a match there.

You probably won’t be able to find DC equivalents for all of the items on your list, but the more you can find, the less energy you will lose.

Pro tip: Almost everything that runs off of batteries (phone, laptop, camera, etc.) is using DC power. Most of these things come with AC plugs for your household use, but they usually have a built in converter to get that to DC power. This is what that large brick in the power cord to your laptop is. For these items, it is often possible to find a car or airplane charger that runs off a cigarette lighter. If you only have a few AC items that you plan on running, it is often more economical (and efficient) to buy these accessories rather than going through the trouble of installing a DC to AC inverter.

Watts, Volts and Amp-Hours

Once you have a more accurate idea of the types of electronics you want, it’s time to do some math. For each item on your list, determine how much power the item draws per hour, and how many hours you plan to use it per day. Check the technical specifications online or in your owner’s manual. Then use these numbers to determine total energy usage.

Tech specs can be confusing, because not all products list them the in the same format. Don’t get too overwhelmed. The most common abbreviations you will come across are:

  • Volts (V)
  • Watts (W)
  • Amps (A)
  • Amp-Hours (Ah) ↠ see below

Because this is a beginner guide, we are not going to get too in-depth about what watts, volts, and amps are. You will read more about them later in the series or in more advanced posts. For the purpose of calculating energy usage, what you do need to know is:

Watts = Amps x Volts

 We will use this formula to get all of our numbers in to amps so that we can figure out how much power we need.

Amp-Hours (Ah)

Amp-hours are different from Amps, which might be confusing at first. If you run a light for an hour, it will use less energy than if you use it for three hours. How is this measured? By accounting for how much power is used over a set period of time. Amp-hour is actually pretty descriptive once you know this. One amp-hour is how much power it takes to draw one amp for an hour. If you have a light that draws 2.5 amps, in one hour it will use 2.5 amp-hours. In two hours it will use 5 amp-hours, and so on. Battery capacity is measured in amp-hours. A battery that has 100ah of capacity could run a 1 amp device for 100 hours, or a 5 amp device for 20 hours, etc.

Our end goal is to figure out how many amp-hours we need so we can size our electrical system around that number. 

Real-world examples on how to calculate power usage:

LED Light Strip (DC Power)

Chances are, you’re going to want some lights to brighten up the van at night. In this example, we’ve chosen a 16.4’ LED light strip that will be hung on the ceiling. Based on the product description, you can see that this light strip uses 12V of energy and 24W to power the entire strip. Because all of the information is given in the description, it is a straight-forward example.

To calculate the amps per hour, use the following equation: Watts/Volts= Amps

24 Watts /12 Volts = 2A

Then estimate approximately how many hours the lights will be on per day. In this example we will use 6 hours.

2A x 6 hours = 12 Ah per day

LED light strips can be cut to size. If you were only looking to use half the number of lights (8.2′ instead of 16.4′), then divide this number in half.

1A x 6 hours = 6 Ah per day


WeBoost Drive 4G-X Cell Signal Booster
(DC Power)

WeBooost is a company that sells cell phone signal boosters. In this case, the website did not list the exact technical specifications. However, when clicking on the PDF spec sheet, we were able to find a chart with the Amps listed next to ‘power.’

In this case, all you need to do is estimate how many hours per day the cell signal booster will be on and multiply it by the amps:

2.5 amps x 4 hours = 10Ah per day


2017 Macbook Pro (AC Power)

For the 2017 Macbook Pro, we searched the Apple.com website and were unable to find out how many Amps the computer was using. Fortunately, electronic items often list their power consumption specs right on the power adapter. Using these specs we are able to calculate that if the computer is in use 3 hours per day, it will use 9Ah of power.

3 amps x 3 hours = 9Ah per day

However, because the computer plugs into a household outlet, we know that it is using AC power. It will be necessary to plug the computer into an inverter rather than using energy directly from our deep-cycle batteries. As a rough estimate, there is about 10% efficiency loss when using an AC inverter. In order to account for this energy loss, multiply the amp-hours per day by 1.1

3 amps x 1.1 (inverter) x3 hours =  9.9Ah per day


Lenovo Thinkpad P50 Laptop (AC power)

Like the MacBook pro, we were able to find the power information for this laptop printed directly on the power adapter. If the information is not listed here, go to the manufacturer’s website and look for technical specifications. It is easy to calculate how many amps will be used per day by estimating how many hours the laptop will be in use and multiplying this by amps.

8.5 amps x 3 hours = 25.5Ah

Once again, there will be a slight power loss of about 10% due to the power inverter that an AC powered device will have to be plugged into.

(8.5 amps x 1.1) x 3 hours = ~28Ah


NorCold NRF Portable Refrigerator (DC Power)

Refrigerators can be trickier to calculate because they are not always on. At first glance, one can assume that a refrigerator will be running 24/7. However, refrigerators use a thermometer to calculate how cold it is on the inside. When the temperature rises above a certain level, a compressor will click on and you will be able to hear the refrigerator ‘running’ until it cools down. Once the refrigerator has cooled below a certain level, the compressor will click off and remain that way until the inside gets warm again.

A compressor will click on and off several times throughout the hour. In extremely hot environments, a refrigerator could be running close to 100% of the time. In the winter, it will be running significantly less. Each refrigerator is going to be very different in how frequently it runs. Some brands have general specs listed on their websites to help find this information.

It is very difficult to predict exactly how often the refrigerator will be running, but it is possible to get a rough estimate. In this example we will calculate the approximate energy usage of a Norcold portable refrigerator. Norcold has very readable tech specs listed on their website. Efficiency is going to be different for the summer and winter, so we are going to calculate both to compare. Based off the tech specs we can see that the refrigerator is drawing 4.8amps of power.

During the summer, we are going to estimate that the compressor is clicked on for 15 minutes of every hour. This means the fridge will be drawing power 8 out of the 24 hours per day.

4.8 x 8 hours = 38.4Ah (15 min per hour summertime)

In the winter, the refrigerator will be running much less frequently. In this example we estimate the refrigerator will be on for 5 minutes of every hour. This is approximately 2.9 hours per day.

4.8 x 2.9 hours = ~14Ah (5 min per hour wintertime)

Because we do plan to travel in the summer months, we will wire our van according to the ‘worst case’ scenario of close to 40amps each day to run the refrigerator.


Checklist of Electronic Devices
This checklist will help decide what to pack

Real-world example of total power usage

Now that we’ve successfully determined the power demands of our four products (LED lights, cell signal booster, laptops and refrigerator) let’s figure out how to put it all together. We’ve calculated the following energy needs:

ElectronicsAmpsUsage Per Day
(hours)
Power Loss
(AC)
EquationTotal Energy Usage
(Ah per day)
Cell Signal Booster2.54None2.5 x 410
LED Light Strip26None2 x 612
MacBook Pro3310%(3 x 1.1) x 39.9
Lenovo ThinkPad8.5310%(8.5 x 1.1) x 328.05
Norcold Refrigerator (Winter)4.82.9None2.9 x 814
Norcold Refrigerator (Summer)4.88None4.8 x 838.4
Total (Summer)73.95Ah
Total (Winter)98.35Ah

Based off our rough estimates, on a daily basis we will use approximately 74amps of power in the winter and 98amps of power in the summer. Keep in mind that your real-world energy needs are going to differ from the total energy required depending on how you plan to collect and store that power.

Next Steps: How to get Power

Now that you know how much power is necessary, it’s time to start planning out how to get that power. These articles will help you with the next steps of powering a van:

  1. Calculating how much energy you need to live in a van
  2. How to collect electricity when living in a van
  3. Solar panel and charge controller basics
  4. Battery basics: finding the right battery for your campervan (COMING SOON)
  5. How to wire electronics: hooking up your van’s electrical system (COMING SOON)

Still have questions? Comment below and let us know how to improve this article.

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