Doing an RV energy audit is the first step toward taking your RVing adventures off grid and having the power you need. We love avoiding camping fees and crowded campgrounds and now live off-grid most of the year. We have been doing this for many years and have spent a lot of time developing and tweaking off-grid electrical systems to perform their very best.
Today, we’ll help you learn how to do an accurate RV energy audit and why they’re necessary. Let’s get started!
What Is an RV Energy Audit?
An energy audit is a process of inspecting and analyzing an RV’s energy use. The audit typically includes a review of the RVs energy consumption data, an inspection of the existing systems and equipment, and an analysis of the RV’s energy efficiency.
The goal of an RV energy audit is to identify how much power the RV uses in everyday use and identify areas where energy consumption could be reduced.
Why Should You Do an RV Energy Audit?
One reason to do an RV energy audit is if you’re preparing to upgrade your electrical system with batteries, inverters, and solar power. You need to know how much power you use to determine how helpful it is to install solar panels on your roof. Ultimately, you want to harness enough energy from the sun to replenish your battery bank.
This calculation also helps you understand the battery bank size you need to install. When you have a system that’s too small, you’ll constantly worry about draining your batteries. On the other hand, you’ll overspend on batteries with an enormous system and carry around extra weight. Like Goldilocks, you want your system to be just right.
We will dive into how to do an audit in this article shortly, but if you are considering adding solar power, the next step is to determine power generation. Our article all about how much solar power you need, will help you figure this out after you perform your audit.
How Do You Measure Power Consumption?
There are a few ways to measure your power consumption; some are more effective and precise than others. Many electronics have a stamp listing their wattage. However, these numbers are typically the max wattage of the appliance, not what you’ll see while using it.
If you want a more precise measurement, you may use an energy usage meter. For AC appliances, these devices plug into an outlet and display how much power the appliance is using. This gives you one of the most accurate measurements for that device. You can also install battery meters that will measure the existing energy being consumed from the batteries.
Pro Tip: Power your rig by uncovering How to Find Reputable RV Solar Installers Near You.
How To Do An RV Electrical Audit
If you’re considering adding solar power to your RV, it’s important first to perform a thorough system audit to determine your energy needs. This will help ensure that the solar panels and accompanying equipment you install will be sufficient to power all of your electrical appliances and devices while on the road. By assessing your energy requirements ahead of time, you’ll be able to make informed decisions about the size and type of solar system that will work best for your specific needs, as well as avoid potential issues with insufficient power supply down the line.
In the audit, you will be trying to determine how much energy you use so you can offset it with solar. There are two primary methods for completing an energy audit:
Method 1 – Use Your RV and Add Monitoring
If you already have an RV that you are adding solar to, figuring out how much power you need is as simple as using your RV. If you don’t have an RV yet, I recommend waiting. This way you can use Method 1 as it will be the most accurate. Otherwise, if you still want to determine your solar needs without owning an RV yet, skip to Method 2.
To Figure Out Battery Power Use
To get the best results, I recommend adding your first solar component to your electrical system (even though you don’t have solar yet). The component I am talking about is the battery monitor. This is one of the most critical pieces of a solar system.
Knowing your battery’s capacity is essential, but a battery monitor can also be used to figure out how much energy you use. I highly recommend the Victron BMV 712 Battery Monitor Unit. This unit includes a shunt that installs on the negative line between the battery and RV. It also has a computer that calculates all of the energy into and out of the batteries.
- Victron Energy BMV-712 Smart Battery Monitor (Grey) is a high...
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This device monitors the current into and out of the system to give you a very accurate state of charge of the batteries. This is critical to a solar system as the batteries are the system’s heart.
Power Measuring and Mathematics
Once you have your battery monitor installed, get the batteries fully charged. Then turn off the charger and use the RV. Usually, you can turn off the charger circuit from the RV’s breaker panel.
Watch your battery power level with the meter and plan to recharge them when they reach 50% of their capacity with lead-acid or 80% with lithium (only 20% Left). Note how long you ran before hitting the 50% (20% for lithium) mark. Then read out the Amp-hours used from the battery meter.
Now take the Amp-hours consumed and multiply that number by the system’s nominal voltage (usually 12.6V for lead acid or 13V for lithium). This will give you the Watt-hours.
Example: 150Ah used x 12.6V = 1890 Watt hours
Note how long it took before you needed to recharge the batteries. If it was 12 hours, then you should double the number of Watt-hours to meet your 24-hour power needs.
Remember there are other power draws you might have yet to account for. You may not have used fans or a furnace if it was not hot or cold outside. In this case, you’ll need to add the following energy numbers to your equation:
Ceiling Vent Fan-Tastic Fan running 12 hours: 720 Watt-hours
Furnace 50% duty cycle running overnight: 1200 Watt-hours
Example: The battery meter said 80 Amp hours used in 12 hours, so…
80Ah x 12.6V = 1008Wh
If you weren’t using the fan, for example, when you noted the Amp-hours consumed, you’ll still want to account for that energy usage when calculating your overall needs. So, add the 720Wh to your total…
720Wh + 1008 Wh = 1728 Watt-hours of battery energy needed
Again, this was calculated for 12 hours of use, so you can multiply the total Watt-hours by 2 to get a 24-hour estimate.
To Figure Out AC Power Use
Now you need to determine if you will use an inverter to power AC appliances. The inverter converts the battery power to an AC household current. You can power computers, microwaves, and pretty much anything else you plug in with AC power. If you use AC appliances, you must figure out how much power you use on the AC side.
Like with the battery meter, one of the easiest ways to determine your RV’s energy consumption is with a meter. You’ll want one that reads all the power used by the RV, like the Watchdog EPO Surge Protector.
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This unit has Bluetooth connectivity that gives you exact power use.
Plus, the Watchdog is available in both 30A and 50A models. If you use a unit like this and will be installing an inverter, you do not need to use the battery meter and can leave the battery charger on. The reading you will get will be all power consumed by the RV.
Make sure the RV has been plugged in for at least 24 hours so the batteries are fully charged. Then reset the energy counter on the watchdog (or whatever power meter you’re using), and use the RV as if you are off-grid for 24 hours.
Keep in mind that you will not be able to run your air conditioning. In fact, you should be conservative with all power use if you want to minimize solar needs.
At the end of 24 hours, check the reading on the meter. It will give you a reading in Kilowatt Hours (kWh). We will use this number later.
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Method 2 – Do The Calculations By Hand
I do not recommend this method compared to an energy meter, like Method 1. But if you are trying to get a ballpark number, this might help.
You need to figure out what each appliance uses for power and multiply it by the amount of time it will be operating. Write everything in a spreadsheet to track it and add up the result.
Doing the calculations by hand is tedious and much more error-prone. But it will give you a rough estimate.
This is a less accurate way to get an estimate but it could get you a quick and dirty assessment of power use.
This method might be necessary if you need to run something like a CPAP overnight or other critical equipment in your RV. For these, add the number to the overall estimate or even the real-world data you collected above if it was not included in the test.
To figure watt hours, multiply the appliance’s watts by the time (in hours) it will run. Then add them all together to get your estimated RV solar power need.
Pro Tip: If you are a #VanLife member, find out How Much Solar Power Can You Put on a Van?
Don’t Just Guess When Doing Your RV Energy Audit
You don’t want to guess at your power needs if you will be going off-grid or you might waste money or not have enough generation. Be it an RV or off-grid property, an energy audit is a great first step to understanding your real-world energy needs.
Which method do you prefer? Tell us your thoughts in the comments!
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Carl
Thursday 20th of July 2023
I've pulled my 12V fuses and put a multimeter/current meter across the fuse terminals. You can read the amps on that branch for a few minutes to find the actual amperage. I found may satellite and radio circuits were using the most power. I left the fuses out as I don't use TV/radio.
Mortons on the Move
Thursday 14th of September 2023
That is a great way to check individual branches for sure!