RV Solar: Part 1 - Introduction & Goals
Installing solar panels on your RV is essential for boondocking off-grid. We've learned so much in the last year!
In this post, I'll talk through how we approached installing solar on our RV, and why we made some of the decisions we did. You may not make the same decisions - every situation is unique - but hopefully the thought process will help guide you through.
Whether you're planning to order solar from the factory, do a DIY solar install on your RV, or have someone else install it for you, the basics are still important to understand.
Series: RV Solar
Table of Contents
Back in August last year, just after we'd moved into our RV full-time, we did a significant electrical overhaul on the RV. We removed the dealer-supplied 12V lead acid battery and replaced it with 3x 100Ah Battle Born Lithium batteries, and installed a 3,000W inverter capable of powering everything in our RV, including the RV. Then we installed a powerful DC-DC charger to charge our batteries at 40A from our truck whenever we're hooked up. And lastly, we fitted a Progressive Industries EMS-HW30C to protect our electrical system when we connect to shore power.
But there was one big omission: solar.
This post is the first in a series about our solar install. I'm writing this all with the benefit not only of hindsight, but a huge amount of knowledge that I've accumulated over the last 12 months on the road. Although I'm not a qualified installer, between our own installation, helping others with their installations, and the countless hours of research and discussion on solar, the goal is to distill what I have learned for your benefit.
Our preferred style of camping is to boondock as much as possible - not only is it free (yay!), but we've stayed in some stunningly beautiful places, often with no neighbors in sight. But it's very rare to find electrical hookups in remote boondocking spots (although I do know of one exception...). Which means we have to provide our own power.
The 300Ah of Battle Born batteries do a great job of providing the power we need to power lights and appliances, charge phones and laptops, and more. But all batteries need charging eventually. This can be done several ways: such as connecting to shore power at an RV park, plugging in a generator, or using the DC-DC charger when hooked up to the truck. Another option is solar.
We already have the DC-DC charger installed for the truck, but that would take around 7.5 hours to fully charge our batteries. And since we want to boondock, shore power isn't available but we could run a generator - but that's bulky, heavy, loud and just one more thing to maintain. The hum of a generator really undermines the tranquility of a beautiful boondocking spot.
Once installed, solar power is free and silent.
OK, before we jump into our specific situation, I want to clarify a misunderstanding I often hear - it's subtle but important.
No RV is powered by solar.
An RV may have solar panels, but the RV is powered by the batteries and the batteries are recharged by solar power.
Don't believe me? Try turning on some lights when it's dark outside - there's no solar power coming in, yet the lights work. But if you use too much power, you'll drain the batteries. Then you'll have to wait until the sun comes up - the solar panels will then begin to charge your batteries, which in turn will power your RV again.
Why is this important? I often hear phrases like "you need 150W of solar for every 100Ah of battery capacity" - with ratios usually varying from 1:1 to 2:1. The reality is there is no magic ratio, although somewhere in that range is usually a good starting point.
You need enough charging capacity (either solar alone, or supplemented by a generator, etc) to meet your electrical consumption over time. You need enough battery capacity to power your RV between charges.
So let's say we use 2kWh per day on average, we would need solar panels capable of providing an average of at least 2kWh per day. For the purposes of this example, we might decide that 500W of solar panels would be sufficient to do that on a sunny day - in reality, you need to adjust for time of year, etc. Now let's say on a cloudy day, our 500W of solar panels only generate 1kWh per day. That means our batteries will deplete by 1kWh per day. If we want to survive 3 cloudy days in a row without pulling out the generator then we need to ensure our batteries have a capacity of at least 3kWh.
A good analogy is the gas tank on your car. A bigger gas tank allows you to last longer between fill-ups. But a bigger gas tank takes longer to fill up with the same size hose. More solar panels is like having a bigger hose - it'll fill up the tank faster. As long as you generate more solar power than you consume, your batteries are there to tide you over between charging (overnight, cloudy days, etc).
Now that we've had our little theory lesson, we can work out how much solar we need, right?
When we were planning this, we hadn't started boondocking. We'd evaluated our electrical devices and appliances, so we had some idea as to how much power we'd use, but we didn't know for sure. With the benefit of experience, it's easier for me now to estimate how much power a particular RV might use in a day by sitting down and chatting with the owner about their habits.
But we didn't know back then. It would have been very easy for us to misjudge the amount of solar we needed.
So we started with the easiest thing. Do nothing. Well, not quite nothing, but we'll get to that shortly.
The point is that it's much easier to assess how much power you think use when you start measuring how much power you actually use! So that's what we did.
Like we talked about in the electrical upgrade series, there are so many ways to configure a solar setup, that each install is almost unique. It really depends on you and what you want. To give you an idea, try asking yourself some of these questions:
- How much money are you prepared to spend?
- Will you do the install yourself, or have someone else do it?
- How much unobstructed space do you have on your roof?
- How much battery capacity do you have?
- Are you willing to climb on the roof to tilt the panels before / after moving the RV?
- Are you willing to deploy a portable solar panel on the ground near your RV?
- Does your RV have any existing equipment you need to integrate with?
- Do you want all the luxuries of shore power even when off-grid?
As you can see, a lot to think about!
Adventurous Tip: Even if you're not planning to do the installation yourself, sharing your answers to the questions above will really help your installer build the right system for you.
We drew up a list of what we wanted, to help guide our design process:
- Quantity: We intend to boondock >90% of the time, but we don't expect to be able to run our AC all day while boondocking. It should provide enough power to let us live comfortably inside our RV, including occasional use of heavy appliances such as the Instant Pot and the microwave - after all, we did spend all that money for a big inverter!
- Simplicity: We intend to move frequently, so the simpler the better. In particular, I'm not keen on climbing up on the roof to tilt panels every time we reach a new spot, only to have to go back up there and drop them down again before we move. It's a personal preference, but that's our stance.
- Scalability: It's reasonable to assume that our needs might change over time. Perhaps our electricity demands will increase (like, for example, when we bought an AeroGarden), or our generation potential will decrease (if, for example, we travel to Alaska). We want our system to have room for growth - this isn't the time to "go big or go home", but instead to "start with the minimum and add when you need it".
I just want to touch on the top of quantity for a second, because it's a key one - how many panels to install is one of the most important decisions. Solar panels are rated based on their maximum output - but this is rarely achieved. As you might expect, it depends on the weather, time of day and critically, time of year. Strong midday sun in mid-summer will produce close to the rated maximum, while a cloudy morning in winter might produce almost nothing.
In reality, for full-timers like us, this means that the energy production will fluctuate during the year - higher in summer, and lower in winter. We want a system with sufficient production to meet our demands in winter, which means in summer we will likely have an excess. Having lived with solar for a while now, this means that in winter (or extended cloudy days in summer) we rely on propane for our water heater and stovetop kettle - in summer, with an abundance of power, we can use our electric water heater and electric kettle to save propane.
As with requirements, your constraints are likely unique to you. A 45ft Class A motorhome with huge amounts of roof space is a very different prospect to a 12ft Airstream Basecamp.
Ours boiled down to just three:
- Cost: We don't want to spend more than we have to, but we want to spend enough to do it right. Safety is paramount.
- Space: The roof of our 25ft RV isn't huge, and we don't want to cover the entire thing with panels - we'd like to leave enough space that we can walk around for cleaning and maintenance.
- Integration: We already have (and really like) the Victron CCGX and so would like our solar system to play nicely with that too. It's useful to be able to monitor the solar, and it keeps everything in one place.
Now we know what we're dealing with, let's boil it down - it's nothing too crazy!
Essentially we want enough solar power that we can boondock comfortably off-grid in our RV year-round, acknowledging that in winter we may rely on propane for heating water. The system should work with our existing electrical components (e.g. the Victron CCGX) if possible. We're interested in roof-top panels, but not tilting and making sure to leave enough space both for cleaning / maintenance and potential future growth in the system.
Back in August last year when we came up with this plan, we had just finished our big electrical upgrade and were flying off to Europe to visit friends and family for 6 weeks. When we returned at the start of October, we'd be hitting the road straightaway, heading first to the Albuquerque Balloon Fiesta, and then on to NomadFEST.
Since we had no time to do a rooftop installation, we embraced the opportunity to learn how much power we really needed. But we knew we needed some solar power. Even without a generator, the DC-DC charger on the truck would give us an emergency "get out of jail free" card if we needed to charge the batteries.
So we decided to start with a Renogy 100W portable solar panel - but make sure to read our next post to see why we bought one without a charge controller. We were pretty sure it wouldn't be enough power for us, especially in winter, but it would be a start. During this time we could see how much power we needed and design a rooftop system accordingly.
This first blog post was really just setting the scene - thinking through what we needed and how best to achieve it. If you're considering a solar install on your RV, maybe it's given you a few ideas to consider. Even if you're not planning on doing the installation yourself, knowing a little bit about solar can really help when speaking with an installer about what you want.
If I can leave you with two takeaways from this post, it would be these:
- Try and accurately assess how much power you use each day, as that will guide how much solar you need. Consider doing an electrical audit if you haven't already.
- Decide what's important to you. Maybe it's price, or weight, or space? Maybe it's not having to think about solar ever again and just knowing you'll have enough power? Maybe it's something simple so you can run the generator every few days rather than every day.
Join us in the next blog post when I'll be talking through how we hooked up a portable solar panel to our Outdoors RV 21RBS. We'll be discussing solar charge controllers, the reversed polarity of Zamp's connectors, and wiring up an Anderson connector.
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