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.
Fortunately, you don’t need to learn everything in order to gain the benefits of electricity and design your electrical system.
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 as well as be able to estimate how many solar panels you need.
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. 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 single way to use 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 vs. 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 (we didn’t feel the need for 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 and their alternatives
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 actually 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.
Coffee maker: There are many efficient water-heating systems that you can make pour-over, French press, or perculated 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 device is before running some numbers and going out to buy a massive solar setup.
How To Calculate Energy Needs
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 charts full of nonsense! 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:
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 for a specific voltage. 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. The first example is 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.
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 * 3.5 hours = 7Ah 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 * 3.5 hours = 3.5Ah per day
WeBoost Drive 4G-X Cell Signal Booster
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 * 4 hours = 10Ah per day
Computer- 2017 Macbook Pro (AC Power)
For the Macbook, Apple.com doesn’t list any power consumption information. Fortunately, there are a couple of other ways to find the power draw.
The most accurate way is to buy a Kill A Watt electricity meter and measure real-world electricity use. This is a device that you plug any AC device into and then plug the meter into a standard outlet. It will measure in Amps (or Watts) how much electricity your computer is using in real time as well as over a cumulative Ah over a set period of time. Just plug in your computer and use as normal to get an idea of how much power you’re using.
If that isn’t an option or you want to try something a bit more challenging, electronic items often list their power consumption specs right on the power adapter. This adapter is listing it’s maximum output potential. The tricky part is that computers aren’t usually drawing maximum power unless they are charging the battery along with running power hungry programs. Once your battery is charged, it will only be drawing a portion of the max output to keep the laptop running.
Using the specs on the computer we can estimate the maximum amount of power a 2017 Macbook Pro will use. We’ll say it’s running some intense programs and charging the battery 3 hours per day (and unplugged, running the same programs it’ll likely go another 4-6, so a full work day).
We need to use the highest rated spec, which is the 20.3V, 3A. First, we have to find what amps the 20.3V, 3A output is when it is coming from 12V batteries. We do this by converting to watts.
20.3V * 3A = 61 watts
61W/12V= 5 amps
So when using full power, it’s drawing about 5A from our 12V batteries. Now we multiply that by hours we plan on drawing this much power
5 amps * 3 hours = 15Ah 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
5 amps * 1.1 (inverter loss) * 3 hours = 16.5Ah per day
NorCold NRF Portable Refrigerator (DC Power)
Refrigerators can also be tricky 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 difficult to predict exactly how often the refrigerator will be running, but it is possible to get a rough estimate. In this example we calculate the approximate energy usage of a Norcold portable refrigerator. Norcold has tech specs listed on their website. Efficiency is going to be different for the summer and winter, so we 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 estimated 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 * 8 hours = 38.4Ah (15 min per hour summertime)
In the winter, the refrigerator will be running 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 * 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.
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:
|Electronics||Amps||Usage Per Day|
|Equation||Total Energy Usage |
(Ah per day)
|Cell Signal Booster||2.5||4||None||2.5 x 4||10|
|LED Light Strip||2||6||None||2 x 6||12|
|MacBook Pro||3||3||10%||(3 x 1.1) x 3||9.9|
|Lenovo ThinkPad||8.5||3||10%||(8.5 x 1.1) x 3||28.05|
|Norcold Refrigerator (Winter)||4.8||2.9||None||2.9 x 8||14|
|Norcold Refrigerator (Summer)||4.8||8||None||4.8 x 8||38.4|
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.