It’s a more accurate measurement of how much actual electricity you have. There is a lot of different components that have variations on this. Recommended Inverter Size Solar Power: Solar panels are sold in varying sizes, but a 100 watt panel is a commonly found size – particularly for RVs. Thank you for such a well laid out info site, W/ LINKS! Your calculator is GREAT! This is the more expensive option, but allows more flexibility in input wiring. And on days I do get it, I can put out my 5th portable panel and dump 20 AMPS an hour into the lithium’s when I can. So that’s the amount of power that it needs.  Rigid Monocrystalline A lot of this stuff is variable and that’s why the solar diagrams you see online get kind of wonky and complicated because they’re for very specific set ups. Laptops are another variable component in that they’re only pulling their max watts. Which Size: The most popular motorhome solar panel kit we sell is the 120w MPPT kit.This kit is currently a good compromise in power, price and size. DIY wiring diagrams for 100W, 200W, 300W, 400W, 600W, 800W kits. Are there losses with multiple batteries? If you’re running things like an electric heater, include that in your list of devices for winter. It’s just so crazy expensive. If I am consuming a certain amount of power throughout the day, then the solar panels alone must be able to source that power. Read our, Large Systems: Wiring Diagram (AGM Batteries), Large Systems: Wiring Diagram (Lithium Batteries). At first I was gonna run 2 battery banks (as I don’t have same batteries/ ages/use cases, types) but this build is turning into a nightmare (even though I can isolate them for charging – but only PWN chargers can I find with dual battery outputs that never charge simultaneously – bad for different batteries).  Rigid Monocrystalline AGM and FLA batteries should only be discharged up to 50%. We have a fridge, and I know this fridge draws 3.9 amps. Now I’m thinking scrap the [free] group 27 deep cycle battery with ~80 amp-hours capacity and just going with 3 (maybe 4) 35 amp-hour AGM in parallel (again a space issue – fitting “short” batteries under the frame). So as you’re picking one out it’s ok to look at the specifications on this. She’ll charge that thing for 2 hours and then she’ll run it for another 3 or 4 because it’s battery is so much better. There is further reading on all parts of the system, extras to install tips and advice on all things electric! There are many differences between these batteries. Now I’m wondering, and what brought me to your site, is if there’s a benefit from multiple batteries? I know they can be discharged more than their AGM counterparts, but that still seems rather low. I would like to know how I add alternator charging as I drive as well as shore power charging at RV parks. From DC it’s 170 watts, accounting for the inefficiency it’s 187 watt hours because it’s running off an inverter. For instance, if you need 150W of power, but your system is only 75% efficient, then you would need 200W of panels to get 150W into the batteries. I have a setup that’s going to be all DC, no AC required. I plan on building a skoolie in the future, and am toying with the idea of running 24v instead of 12v. If 300 watt diag (for example) you would have 12v X 3 = 36 volts. But smaller inverters are more efficient. The input depends on many variables but is generally always higher. A gaming laptop is a lot more efficient than one of the towers just because the CPU is designed to be able to run off the battery. Very informative, thanks for sharing! What you’re going to want to do is everything that uses electricity, you’re going to write down. And it’s our camper van solar system calculator. The Big Info Index Solar Panel Calculator Generally, you will be able to go down a size from this. Used to reduce electricity bill. There is more detail in this in our charge controller article if you want to know. A PWM controller uses less complicated and less efficient technology. This calculator kind of walks you through the order that you need to figure things out in when you’re sizing this. So we’re going to say 47 watts for my fridge. Some days I might not be running my laptop, some days I might be running a little more. Similar thoughts… but I’m struggling with the charge controller sizing myself… given other elements are fixed (due to size). Then build your system to the largest number. If I use this to calculate, would I just halve the Ah needed for the battery for a 24v setup? This calculator is meant for camper van conversions, RVs and small off-grid solar systems. the system can recharge the batteries the rest of the day. In your 400W diagram, you have the following battery recommendations: 200Ah (x2) Battery (AGM option) In cold weather, the compressor in a fridge may only be. Great site! So this component is our general go-to if we were to build a camper van with our own money this is how we would use it. Hey! The calculator takes into account the power consumption you use in your caravan/RV and your travel destinations. Also any tips on mounting ridged palels to roof. So they’re a little more flexible in their use. Because they’re meant to be plugged into a wall. Those things are not great to be battery powered. This electrical usage table will have a number of rows equal to the number of electrical components we use on a typical day.The first column is the name of each electrical device. Thanks! 2) Get a MPPT charge controller. Or a refrigerator that cycles during the day. Solar.com has substantially upgraded its solar savings calculator to provide more accurate cost and savings estimates with solar. With the beefy internals, I figure, I can add more panels and batteries later. There’s two of those so we’ll say 6 hours per day. Now, the PWM controllers are significantly cheaper. This calculator may also come in handy. We do have this in there. Now your solar panels, they only have a window of opportunity to gather your electricity. They are also quite a bit more expensive, but they last longer. Hope that helps! Alternatively, you may choose to purchase a pre-configured solar panel kit. You kind of want to make sure that those are running efficiently. The third co… The charge controller can do this with 18V or 24V or 36V or a range of voltage inputs (depending on the controller) and use it to charge 12V batteries.  Renogy 200W Solar Kit (MPPT charge controller) You might find that helpful. Thank you so much! Those are the only things I plan on running off the inverter. The problem with that is then you also need to make sure you have enough panels to run that once is does drop for two days worth of use. A lithium battery can be safely discharged up to 90% without shortening its lifespan. Is this correct? This is kind of just a guide for how to use the calculator itself and what some of the different numbers and that kind of thing mean. Thanks again. You are probably still planning to use power like you would in a house. Any of my wire runs are no more than 6-8 ft… so #12 AWG should be fine for wiring, but I’m way confused on this current/amp boost that will happen between CC and batteries in a 12 volt system??? example: looking at a microwave that says it uses 720 watts. If you’re in the hot weather all the time you might want to boost that even double it up to 16 hours. This is how the high efficiency fridges and the fridge in your house work. This is a very convenient way to transport and use solar panels, but it doesn’t help them to face directly into the sun at all times. Click the to add a new row.  100Ah (x1) Battery (Lithium option), Inverter (use smallest size required) Would you not want 200Ah with the lithium option? Than you might be looking at PWM controllers for anything under about 400 watts. Monocrystalline cells are made up of a single silicon crystal; polycrystalline comprise fragments of silicon. The “load” terminals on the CC are in fact pulling energy from the battery, not the solar panels. I have the same solar charge controller shown in your diagram, but I can’t find the specs for it. A cheaper option is to go with a battery isolator. Say this number comes out to 25 amps, but you know your MPPT specs say that it can go to 240 watts and you only have 220 watts of solar, that charge controller can be a 20 amp charge controller. And those don’t even need to be charged up all the way at the end of each day. Batteries are the most expensive component in your electrical system, so you don’t want to wear those out too quickly. This is excellent. Fill out the calculator below to find out how many solar panels you need for your DIY solar panel system. so I use it for 10 minutes, thats 0.6 of an hour so 720/0.6 = wH of use?  150Ah (x2) Battery (AGM option) Everyone is going to be different so maybe you’ll find one 240 watt solar instead of two 100 watt panels. Solar calculator for RV or camper van conversions. This would make your input at 18V and you would be getting more advantage of a PWM controller without loosing significant power. Both of those have similar profiles in that you don’t want to discharge them more than 50%.  B2B charger (solar CC included, incompatible with lithium) solar power as a function of time, in kWh or Wh, that your solar panel can produce, taking into account its rated power and solar energy available at your place.. Because each day is like its own reset in terms of the electricity that you’re going to use. Read our wiring post to determine the proper wire size for your build. If DIY solar power is intimidating to you, we recommend looking at solar powered generators which are plug and play devices that require little to no wiring. There’s no problems with going more solar. Now a lot of systems use amps just because that’s how 12 volt systems have always been measured in the past, and in vehicles it’s a good transition. (IMO), I used your Calculator and was wondering on the Solar Panels could i use a 360 Panel instead of 3- 100 Watt panels? Either way works, it doesn’t really matter. Hey Ross, good catch! I find that to be a little redundant. You’re not going to want to run a coffee maker and you’re not going to want to run a toaster oven like I said.  Battery isolator But with a 20% discharge you need a lot bigger battery if you’re only going to be discharging it the same amount. You will likely need to purchase a battery, inverter, fuses and wires* separately. “12V” solar panels typically output between 18-22V, which fluctuates based on external factors (sun, temperature, angle, etc). Solar, Alternator and shore power. Usually 12, 24, or 48 volts.  Rigid Monocrystalline There’s a lot of little details. Because your alternative is to jump up to a 200 amp hour lithium battery and spend another grand on that. In series wouldn’t the CC stepping down use some of the potential power? If you do a lot of dry camping then you know that battery life is one of the most important things you must plan for, especially if you have a small battery bank. A lot of people will run off the load terminals to the fuse box. But if you’re twice daily using an 1800W induction burner, you’ll want a large battery bank to handle the heavy loads or else will be replacing your expensive batteries quickly. Say hey, here’s all my numbers, this is my daily power usage. This is the maximum power you will expect to use on any given day. I’m not sure exactly where in the formula the 1.2 and 1.3 come in the way we set up the calculator (it was awhile ago), but you’ll notice that with an MPPT system, you need less wattage in panels than a PWM one because MPPT controllers are more efficient. So once you have your battery, your power storage, you know your power storage can discharge a full day’s use, you can always boost that if you want. I might pick up a 400 watt inverter just because they’re easier to find, especially ones that plug into the batteries. On-grid solar system involves solar panels and inverter. Solar kits normally come with solar panels, a charge controller, and z-brackets for mounting. Make sure you wire your batteries in a parallel string that maximizes their lifespan: http://www.smartgauge.co.uk/batt_con.html. Thanks for the great article. Your fridge will not be running 24 hours per day. No backup as there is no battery. Simply select the type of car or motorhome you have, and select your towing unit if you’ll be using one. The numbers you’re looking at function in this purpose. In your controller diagram you show the BATT as being the far right terminals of the PMW controller. If you want more information on electricity, head over to our electrical home page. If you have, let’s say you’re going to be in the desert southwest most of the time and you know you’re going to have tilt mount panels maybe you’ll see 6 hours of sun. Enter the total Amps that your Solar Panels will produce all together.  Wires and fuses*, Alternator Charging (optional – choose one) So this calculator at the top, if you put your amps and your volts, it does a simple calculation and gives you your watts. This is a theoretical guide to give you some indication of what will suit your needs. Take a moment to think about the electrical appliances and accessories you plan to use Decide on the part of the year you will be using the equipment (spring to autumn, or the whole year). So, in this case we’ve got 220 watts. I have been really strugling to identify this Each system has several battery options and everything is sized proportionally, so the solar panels, inverter and battery all work optimally together. I think that thing was pulling 2.9 [amps]. So they can’t supply all of that charge throughout the day like your batteries are going to be able to discharge. Using your calculator, rounding up with worst case, I will need a 12v 200 ah battery and 300 watts of panels. Go bigger if you can with this, unless you don’t have enough roof space or if you’re on a significant budget.  Battery isolator (compatible with lithium) Not really necessary in the larger set ups because your battery is better at handling that load anyway. Maybe you’ll say hey, maybe I want to trade in my laptop or before I buy a laptop I’ll get one that’s more efficient. Thanks so much!!! As a general rule, smaller inverters are more efficient. If we’re ok with discharging it up to 50% we can drop that down to a 185 amp hour battery. You show the loads directly tied to the battery. If you want to save all this, down at the bottom of the calculator we have a “print your numbers” button. So if you’ve done all your calculations and you’ve written down your things.  Electrical wire crimp connector We recommend calculating both your summer and winter numbers. So I don’t need anything more than a 200 watt inverter. With that said, for smaller 12V systems, it is often advisable to get a PWM controller and more solar panels get more bang for your buck. That’s a lot of the cooking elements that people try to run off inverters. If you run an AC powered object like my laptop, then that efficiency is going to be reduced so you’re going to have to use more energy to charge the laptop than you would if it were DC powered. It uses a lot of your juice, your electrical power available. ABOUT US I reside in my van all year when not at my sister’s down the street. But in general, if you’re going to go significantly larger, you’re going to want to double check your battery bank size. This is nice to print off to show people. When sizing your RV solar system, If your ideal solar calculations call for 3 solar panels but your roof space only allows for 2 panels. Sadly I’ll be ditching my $800 worth of 200 AH AGM batteries for lithium.  6 way fuse block + bus bar In this example, a 200W or 300W inverter would be fine for a 150W laptop. So when that compressor is off, it’s not using electricity even though the fridge is plugged in. Your email address will not be published. I wish there was any easy formula that said a panel (like a 100 watt panel) would produce x amp-hours of usable power per day, but I can’t. So in this case, to discharge 1127 watt hours per day, we need a 470 amp hour battery if we only want to discharge it 20%. That fridge when it’s drawing power, it’s powering a compressor and that compressor is only kicking on to cool the fridge down to a certain temp and then that compressor turns off. Especially like I said if you’re running short bursts of power. Actual charging times will vary dependingon geographic location, time of year,  angle of the sun relative to the RV solar panel and, weather conditions. And those are in series with the first battery. You still need the CC wired to a battery through the battery terminals. Select whether your device is DC powered or will be using an AC inverter. We recommend reading our post on charge controllers for more information. With that said, it’s usually a lot of work to add more panels on the road so we like doing them all at once. Click the to delete a row. Read our article on inverters for more information.  Solar panel extension cable Here are some tips to cut back on electronic use. Charge Controller Size Inverter 1100W (1200W).  100Ah (x1) Battery (Lithium option), Solar Panel Kits No! mobile power equipment recommendations based on your specific power usage.. At Go Power! It’s a really good quick reference for your camper van. Presuming you have six usable hours of sunlight in one day each 100 watt 5.5 amp panel will generate 33 amp hours … This is relative to how much total capacity the battery has, so larger batteries can discharge more quickly (hence a larger inverter). And that thing is running about 5 hours per day. Hi can anyone tell me where I can buy a cassette toilet /washand basin/shower unit complete for the back of a sprinter. Working voltages normally are 18V, 36V and so on. It is difficult to predict how much wiring each different van build will have and the lengths needed, and we don’t want to have you ordering things that you don’t need.  200Ah (x1) Battery (AGM option) The battery is essential for the system, not just to store energy but to create a balanced energy source (rather than the erratic energy that comes from the sun). The other thing to note is you can always go smaller. Now, those of you who are trying to run desktop gaming stations or something in your camper van, you’ll pretty quickly realize that the processing and the CPU and that type of thing in your gaming tower takes a lot of power.  B2B charger (solar CC included, compatible with lithium), Solar Panel Kits So in this case were using 1127 watt hours per day. If using heaters and fans, it is helpful to do a calculation for a winter month and a summer month (including sun hours below) and use the larger of the two. Posted this on wrong Blog entry. There’s a lot of benefits to lithium batteries. These are just to see which size components and how you want to plug everything together. You can use this as a general guideline while panel shopping. Just want to charge some phones at night and make coffee in the morning. Seems to me that this would not only run the A.C units but would also charge the batteries inside the trailers. Living in a van requires cutting down on unnecessary electronics as much as possible. has a number of ways to help you find the right system for your RV, boat or work truck. So the reason you don’t want to go bigger on your inverter for this is because a bigger power draw is hard on your batteries, it’s going to make them not last as long.  WindyNation 100W Solar Kit (PWM charge controller and battery included). An inverter is less efficient. Now if you want to get your batteries to last longer, you can discharge them to only say, 20%. In 97% of the 10-20 amp PMW controllers I have seen, the BATT is the center set and the LOAD is the far right. This is a helpful starting point for me to figure out what I need. So why is solar_factor greater than 1? As per the Solar panels, we need to pay attention to the working voltage and short-circuit voltage. But if it’s just charging the battery and I’m surfing the internet – 120 [watts]. Remember that the calculator is determining what system size that you need based on your inputs (not how much output you will get from an existing system). These are the component sizes I’m going to go with. So it gets a little overwhelming, but it’s not too bad. It is the smallest size charge controller that you will want to use. Again, we go through all of this on our charge controller post if you want to know details. It is a battery charger that works anytime the sun is out. Go with the smallest inverter that you will need with a bit of wiggle room. Charge Controller Always ensure as many cells as possible are in direct sunlight. Some general rules to follow are: We based our calculations on a 10% efficiency loss that occurs when using an AC inverter. This is my first solar project. Jump To Solar Wiring Diagrams. Basing your calculations at 4 sun hours is a good conservative estimate for most van dwellers’ varying lifestyles. And then the other 2-3 hours that I’m using my laptop it’s running off the battery power that it was charging at 120 watts earlier. The solar sizing calculator will then be able to tell you the minimum and recommended system size, as well as the recommended battery output. The best option is a battery to battery charger, many of which double as a solar charge controller. If you’re in the desert southwest and an angled system you’ll have 6-7 hours of available sun. Suggestions? The solar panel calculator can help you work out what equipment you need to fully charge your next camping, caravaning or off-road adventure. Your wire size is going to vary greatly depending on how far you are running them.  Battery monitor (optional – basic)  Flexible polycrystalline, Charge Controller Hope this helps! So if you notice this number jumps up. Meaning that you get the same amount of theoretical power from two 100W panels in series as you do from two 100W panels in parallel when using an MPPT controller. So the smaller you can go comfortably the better with this. So grab a piece of paper and a pencil and create a table. So 4 sun hours, gives us 220 watts of solar. We also have two phones, and our phones are I think 3 amps but at 5 volt USB so they’re each running about 15 watts and they’re plugged in 3 hours per day. At night when the temperature drops, the compressor won’t be clicking on and off as much. Excellent page guys, nice work. 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