Lets discuss the AC side of your electrical system. What do inverters do, how much power do they draw and how to choose the right one for your van. Use the list below to jump to specific topics. You can find links to all the components we used in our build in the van build shop. Remember, it’s perfectly okay to outsource the wiring of your van to a professional or have a professional inspect your work. We are not professional electricians so take our advice with healthy skepticism. This post contains affiliate links, we earn from qualifying purchases at no cost to you.
What’s an Inverter?
An inverter is a device that changes DC power to AC power. This is the opposite of a converter which changes AC to DC. For a refresher on AC/DC electricity check out this post. But simply put, an inverter will allow you to run standard 120V household electronics off the batteries in your van.
Pure vs. Modified Sine Wave
Inverters will come in two flavors, pure sine waver inverters and modified sine waver inverters. When the inverter changes DC to AC it tries to match the frequency at which 120V AC modulates in the US at 60Hz. Modified sine wave inverters output a stair step pattern that is more power efficient but could possibly damage sensitive AC electronics like computers. Pure sine wave inverters output a much more smooth curve that more closely resembles true AC electricity. Pure sine inverters are more expensive than modified sine inverters and are slightly less efficient, but they will not damage any devices.
Power Output & Consumption
Inverters output is measured in watts and for a typical van build you should be considering inverters in the 500W – 2000W range. All inverters will have a peak or surge rating and continuous rating. The continuous rating is most likely advertised wattage ie. 1000W and is what the device is capable of outputting for extended periods of time. The surge or peak rating is what the device can handle for a few seconds, usually during startup, and is typically 20-50% higher then the continuous wattage rating.
Remember Watts = Amps x Volts so you can figure out how much power your inverter will consume by dividing the inverter watts by 12 then estimating how many hours per day you plan to use the inverter. For example a 1000W inverter will draw ~83A @ 12V (1000 ÷ 12) while a 2000W inverter will draw twice that amount. Inverters are only 80-90% efficient so its a good idea to add 10-20% to your power consumption estimates. If you then estimate to use the inverter 30 mins a day simply divide 83 by .5 (half an hour) to get ~42 amp hours. This estimate assumes you’re using all 1000 watts the inverter is capable of producing however, most likely you will only be using a fraction of that the majority of the time.
The Right Inverter For You
The best size inverter for your van build will be determined by three things (1) your budget and power needs (2) your batteries and (3) your available space.
Your Budget and Power Needs
Pure sine wave inverters are going to cost more than modified sine wave inverters so first you must ask yourself what kind of electronics are your going to be using with your inverter. If you are charging laptops and expensive camera equipment I would highly consider getting a pure sine inverter however, if you’re only going to be grinding coffee and boiling water, a modified sine inverter might be best for you.
You might be tempted to just buy the biggest inverter you can find just in case you want to run a power saw one day. However, the higher the wattage rating the lower the efficiency so if most of the time your only using 10 Watts off your 3000W inverter, that’s a huge waste of power.
Most electronics will be labeled with the wattage they consume. Simply make sure that you get an inverter big enough to handle your highest wattage device and/or the sum of all the devices you would ever want to run at the same time. Some examples below.
The maximum amperage draw of your inverter cannot exceed the maximum continuous discharge of your batteries. So double check the specifications of your specific batteries before assuming you can power a huge inverter. See our post about batteries for more information.
Your Available Space
Inverters tend to be big and heavy so you’ll want to double check the dimensions of the inverter you’re thinking by buying against your available space. And don’t forget about ventilation; you don’t want to cram your inverter into a closed space, it will need some room to breath and exchange air.
To Your Batteries
Most inverters will come with cables and its totally fine to use them. If you have the means however, you may want to consider upgrading the cables that came with your inverter to a larger gauge. Going up a gauge (and potentially shortening the length of cable) will make a more efficient system that runs cooler. Check out our post about batteries to learn how to crimp your own cables. See the chart below for recommendations on cable and fuse size below.
A good inverter should come with some kind of over current protection built in. Meaning if you plug in something that overpowers the inverter, it will just trip a breaker and reset automatically. However its always a good idea to install a fuse between you inverter and batteries just in case. See the chart below for the recommenced cable and fuse size for different inverters.
To Your Outlets
Most inverters will have outlets on the side of them that you can plug your stuff directly into. If you want to hard wire your inverter to outlets you’ve installed somewhere else in the van then you can cut the female end off of an extension cord. Get yourself an outlet and a blue outlet box from the hardware store for a couple dollars and follow the wiring diagram below.
My Two Cents
Spend the extra coin to get a pure sine inverter, then you never have to second guess what you’re plugging into the outlet. Be honest with yourself about your needs and don’t get a huge inverter if you don’t need it. We have a 1000W inverter and it powers an instant pot, electric kettle and electric hotplate without a problem (not all at the same time of course).
Hope this guide gave you some value and cleared up any confusion. You can find links to all the equipment we used in our van build at our van build shop.