12V electrical systems have been around for a long time in campervans, RVs, cars, boats, so we know for a fact they that are efficient and reliable. But 24V and 48V systems are getting increasingly popular, and are often the subject of heated discussions on social medias.
Cost saving is the number one reason why people choose 24V over 12V, smaller wires are cheaper after all. However, as you’ll see in our cost analysis, saving on wires does NOT translate in 24V systems being necessarily cheaper…
Reading the comments on social media, the race for “more volts” kind of reminds us of the race for “more pixels” with digital cameras (way back, when it was relatively new). The number of pixels was used as the main (and often only) selling point, while actually there are other important variables in the equation to be considered.
After reading this fact-based guide, you will be able to make an informed decision and decide which of 12V, 24V, or 48V electrical system is the best for YOUR needs. Let’s find out!
Table Of Content
- Benefits of higher-voltage electrical systems
- Smaller cables
- Inverter larger than 3000W
- Solar power larger than 1450W
- Smaller solar charge controller
- Drawbacks of higher-voltage electrical systems
- Can’t run 12V appliances directly
- Not compatible with 12V solar array
- 24V components availability
- About 48V electrical systems
- Cost analysis between 12V vs 24V systems
- Small (200Ah | 360W solar | 1000W inverter)
- Medium-Small (400Ah | 540W solar | 2000W)
- Medium-Large (400Ah | 540W solar | 3000W)
- Large (600Ah | 720W | 2000W inverter | Air Con)
- Efficiency
- Conclusion
1. Benefits of higher-voltage electrical systems
1.1. Smaller Cables
1. The amount of current flowing through a wire determines its gauge: small current = small diameter.
(In fact, the length of the wire and the desired voltage drop also impact its gauge, but that’s another topic and you can learn more about that in our Electricity for Dummies section of our Electrical System Guide.)
2. The current flowing through a conductor is inversely proportional to the voltage and obey this equation:
Current (A) = Power (W) ÷ Voltage (V)
3. We can therefore conclude that for the same amount of power, current flowing through a conductor will be halved in a 24V vs 12V electrical system. This allows to use smaller cables for the same amount of voltage drop. As a real-world example, Victron’s Multiplus 3000VA inverter (Amazon | BayMarineSupply | Data Sheet) will draw half the current when running on 24V vs 12V. We can therefore use 2/0 AWG cables instead of 4/0 AWG cables, which are substantially cheaper:
On a side note:
- Smaller cables allow to use smaller breakers, but they cost the same as larger breakers. No saving here, and breakers cost generally more than the section of cables it protects...
- Smaller cables contain less copper, which is harmful to the environment through its life cycle. So that’s a win here!
- Use our Wire Gauge Calculator to find out the correct wire gauge.
1.2. Inverter larger than 3000W
4/0 AWG is the biggest cable gauge available to the consumer, and 4/0 AWG cables can work for an inverter up to 3,000W in a 12V electrical system. Anything above 3,000W and you would have to double the 4/0 cables, but we don’t recommend it as it increases the level of complexity/risk.
If an inverter of more than 3,000W is needed, the next best thing is to switch to a 24V electrical system. This would allow to go up to approximately 5000W inverter with 4/0 AWG cables. That being said: 3000W is a LOT of power in the context of a campervan, so do your homework and make sure you actually need all that power!
1.3. Solar power larger than 1450W
The Victron 250/100 MPPT solar charge controller (Amazon | BayMarineSupply | Data Sheet) is their largest offering and can handle up to 1,450W if hooked to a 12V battery bank. So where do you go next? You guess it, 24V! It then allows a solar array up to 2900W:
1.4. Smaller solar charge controller
For the same-size solar array, a smaller charge controller can be used with a 24V vs 12V electrical system which translates to a cost-saving opportunity. Here’s a screengrab from our MPPT Solar Charge Controller Calculator:
2. Drawbacks of higher-voltage electrical systems
Any voltage conversion comes with energy loss. The larger the conversion, the larger the loss. In a perfect world, all our appliances (e.g. fan, fridge, stove, etc.) would run on the same voltage as the battery bank in order to avoid any voltage conversion. But in the real world, we have to deal with appliances that run on 12V, 24V, 120V AC. To minimize the energy loss associated with voltage conversion, try to choose appliances that run on the same voltage as the battery bank.
2.1. Can’t run 12V appliances directly
Some appliances can be run on 24V, some must be run on 12V. Here’s a quick (not exhaustive) overview:
Can be run on 24V
- Sirocco wall fan (24V/12V)
- Shurflo Water Pump 24V (4008-131-E65) (+$120!)
- Propane Solenoid (AFC-111-24V)
- Espar/Webasto Heater (24V version)
Therefore a 24V electrical system must always includes BOTH a 12V distribution panel AND a 24V distribution panel. The voltage is stepped-down from 24V to 12V using a converter such as the Victron Orion 24/12 DC-DC Converter (Amazon | BayMarineSupply | Data Sheet). The Victron Orion efficiency is between 92% and 95% (per data sheet), which means all 12V appliances will incur 5% to 8% energy loss.
The amount of components (wires, breakers, terminals, etc) is increased, and you now have to manage a “hybrid” electrical system (12V and 24V). This is not exactly begginner-friendly and is more prone to mistakes.
2.2. Not compatible with 12V solar array
The voltage of a charge source must always be higher than the battery bank. Therefore, with a 12V electrical system, a single 12V* solar panel can be used. But with a 24V electrical system, you’ll have to use at least a 24V* solar panel or connect multiple 12V solar panels in series.
* Solar panel’s specified voltage is nominal. In reality, the voltage is higher (e.g. a 12V solar panel actually works near 19V).
2.3. 24V Components availability
24V appliances are not as common. Sure you’ll find them online to build/install your electrical system, but in the eventually of a breakdown, remember that local RV shops rarely have 24V appliances in stock. That means more wait, less vacation.
That’s a real-life story we experienced during our Van Life. Our water pump broke, but fortunately we could find a replacement pretty easily in a local RV store. Easy fix! We were travelling full-time so a breakdown didn’t have much impact on us, but if you’ve got only a few days that’s not great…
2.4. 48V electrical systems for Campervans/RV
While 48V electrical systems can make sense for large systems (houses/cabins), it’s very hard to justify for mobile application such as campervans and RVs. Here’s why:
- Most automotive/marine fuses, breakers, and switches are NOT rated for 48V.
- Your solar array will have to be larger than 48V.
- Charging from the alternator is not easily feasible, unless going for a second 48V alternator.
- Quality, large output, 48V to 12V step-down converters are hard to find.
- Very few appliances can actually run on 48V directly.
- The overall cost will be higher compared to a 24V or 12V system.
In our opinion the cons outweigh the pros, so there’s no real reasons to go for 48V electrical system in a campervan.
3. Cost analysis 12V vs 24V vs 48V electrical systems
When asking people online, cost is the number one reason to go with a 24V electrical system. That being said, we still haven’t come through a real-world detailed cost analysis. So we will obliged and compare the cost of a few campervan electrical systems:
Color Legend:
3.1. Small System (200Ah | 360W solar | 1000W inverter)
The Small System is derived from our (12V) Standard Wiring Diagram:
3.2. Medium-Small System (400Ah | 540W solar | 2000W inverter/charger)
The Medium & Large Systems are derived from our (12V) High-Power Diagram:
3.3. Medium-Large System (400Ah | 540W | 3000W inverter/charger)
3.4. Large System (600Ah | 720W | 2000W inverter | with Air Con.)
*Velit Air Conditioner Kit chosen in the example above. You can learn more about 12V air conditioners in this guide: 12V Battery Powered A/C for Off-The-Grid VanLife.
12V vs 24V Cost Analysis Summary
| SIZE | 12V | 24V |
|---|---|---|
| SMALL (2 x 100Ah Battery | 360W Solar | 1000W Inverter) | $4,696 | $4,790 |
| MED-SMALL (4 x 100Ah Battery | 540W Solar | 2000W Inverter/Charger) | $7,507 | $7,436 |
| MED-LARGE (4 x 100Ah Battery | 540W Solar | 3000W Inverter/Charger) | $7,792 | $7,983 |
| LARGE (6 x 100Ah Battery | 720W Solar | 2000W Inverter/Charger | Air Con) | $9,634 | $9,675 |
As we can see from our analysis, a 24V electrical system is not necessarily cheaper. That’s the case, at least, for campervans where components are tightly packed together. The cost saving on wires is not significant enough to outweigh the cost of additional components (24V to 12V step-down converter, 24V and 12V fuse block) and the cost of 24V components (e.g. the 24V Shureflo water pump costs $120 more at the time of writing this article!).
4. Efficiency
We initially placed efficiency under the section “Benefits of higher-voltage electrical systems“. But digging further into this topic we feel that, once again, it has to be nuanced…
Voltage drop is the energy loss by the flow of current through a wire. With a 24V system, current is halved in some sections of the electrical system. Half the current and twice the voltage translates into 4x less voltage drop, but most people choose to install smaller wires in order to take advantage of that sweet cost saving benefit… so there goes half of the potential efficiency gain. Still a win for 24V though!
Converting to 120V is another source of energy loss. A 24V inverter will be more efficient than a 12V inverter. In the case of the Multiplus, that’s 1% better in the best-case scenario (94% max efficiency at 24V | 93% max efficiency at 12V). At full power (2400W), the 3000VA Multiplus draws 24W more at 12V than 24V. That’s a win for 24V!
For 24V electrical systems, energy loss resulting from the 24V to 12V voltage conversion must then be added. The Victron Orion DC-DC (70A) is listed at 92% max efficiency. Which means that when all the 12V appliances draw 20A (arbitrary real-world number), over 20W of power is lost in heat. That’s win for 12V!
At last, for 24V systems, energy loss from the 12V to 24V voltage conversion (alternator charging) must also be considered. That being said, most DC-to-DC chargers have the same output rating (in Watts) whether it’s for 12V or 24V, so the energy loss occurs on the vehicle side. That’s a win for you, but a loss for the person who pays the gas!
Are 24V electrical systems more efficient than 12V systems? For electrical systems with short distances to cover, not really. For electrical systems with long distances to cover, yes.
5. Conclusion
There are some advantages to higher-voltage electrical systems, no doubt. But 24V or 48V electrical systems are not better than 12V, there are some nuances. In our opinion, in the context of campervans at least, the cost and efficiency is not significant enough to justify a 24V system. Especially with the increased number of components, complexity, and parts availability. But high power requirements can, in some cases, justify a 24V system.
Here is a rule of thumb to decide between 12V, 24V, or 48V for your campervan/RV:
12V System
Choose this if you want:
- Less components (simpler to understand, install and maintain).
- Better parts availability (at installation, but especially down the road).
- 1,450W solar or less.
- 3,000W inverter or less | No A/C.
- 2,000W inverter or less | With A/C.
24V System
Choose this if you want:
- More than 1,450W solar.
- 3,000W inverter | With A/C.
- More than 3,000W inverter | With A/C or not.
- Cost saving alone does not justify a 24V system!
48V System
Choose this if you want:
- Not justified for campervan/RV…
But in the end if you’ve done your homework and fully understand the benefits, drawbacks, and what you’re getting into, then the decision is yours! Happy build 🙂
That’s it for now, see you out there!
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Disclosure: This post contains affiliate links, which means that if you click a product link and buy anything from the merchant (Amazon, eBay, etc.) we will receive a commission fee. The price you pay remains the same, affiliate link or not.
Nomadic 48V Air Conditioners and so called “parking Truck AC” from alibaba for much cheaper (basically mini splits) with 48V option really got me thinking about 48V over 12/24…
Your work on these webpages is very helpful and greatly appreciated. I’m planning my first conversion. An eSprinter. I believe I will be able to use the 113 kWh vehicle battery to keep the house battery system charged. Being a first-timer I’m not really sure how this will affect the 12V vs. 24V decision though I’m strongly leaning toward 12V for first-timer simplicity. One thing I don’t understand: You wrote that for a 12V system:
3,000W inverter or less | No A/C.
2,000W inverter or less | With A/C.
What is the reason for this?
Thanks.
We are using 48V. Big battery, big solar, no gas. The arguments for it when we built it 3 years ago were:
– cheaper batteries (about 70% of a 12v version for the same capacity)
– cheaper mppts. 800w solar + 800w on slides meant 2 x victron 100/20. They generally have their price proportional to amperage, so 0.25 the price there.
– we were planning to run most things on 220, laptops, coffee machine, induction, and it’s a bit better to invert from 48 to 220 than from 12 to 220.
after 3 years of van use at 50% duty cycle, here are the opinions:
– cheap 12v batteries became available in the meantime.
– everything you want on the market is either 12v DC or 220v(110)AC. We have a dc-dc 48-12 step down but it’s somewhat limiting. Adding a 35A air compressor meant also adding a separate step down only for it or it would reset the router.
– can’t charge from alternator. there’s something pricey from safiery, but nothing if you’re in the victron environment. The solution is to have a small 1kw inverter feeding into the Multiplus shore, with probably 30% losses along the way
– we gave up the sliding panels and made the remaining 800 tiltable. the mppt price advantage we had is halved by this.
– we slowly moved stuff from AC to DC in the name of efficiency, and from ~10% 12vDC vs 220AC in the beginning we are now at ~50%.
Would probably go for 12v should we start again today.
You two are remarkable! Built my 12v system on your electrical chart. 4 years and no problems
Thanks, and glad to hear our wiring diagram is serving you well 🙂
cheers
Both of the previous comments are exactly why I’ve been thinking hard about going to 48V. A dedicated 48V alternator would provide ample power with much easier cable routing and enable ‘off grid’ 48V PV equipment that could power less expensive 110V AC appliances. I think this is where you could actually save money over a comparably equipped 12V system. The challenge a couple of years ago was the dedicated alternator, but there has been a lot progress since then.
The item that pushed me to 24V for my second van (and would have me consider 48V) is dedicated alternator charge capability. 24V and 48V systems open up the possibility of very high charge rates and power (>5KW). This in turns really opens up flexibility for things like off-grid AC. E.G. I can drive (or high-idle) for a fairly short period of time to add hours of AC usage (or days of baseline electrical usage). This isn’t possible with at 12V system. That said, designing and installing a system like that isn’t for the faint of heart, and requires a level of battery storage that can handle ≈5KW without breaking 0.5C limits.
Upping the voltage also allows you to start looking at combo AC Inverter + AC Charger + MPPT DC Charger systems, which are quite affordable and seem to have good reliability reports from the offgrid solar world.
e.g. 48v: https://signaturesolar.com/growatt-48v-3kw-150vdc-stackable-off-grid-inverter/
24v: https://watts247.com/product/2-x-spf-3000tl-lvm-24p/
I looked into these enough to confirm that the manufacturer suggests that they can be used in an RV, and that the individual component boards can be swapped out (so the inverter can be more cheaply replaced by itself than needing a whole new unit). Also a full spare could be carried at all times while still being cheaper/smaller than a discrete setup.
I decided to stick to old fashioned 12V and victron components, so I can’t speak personally to these, but on paper they would be a good choice for someone wanting to run a very high power system on a tight budget. If not doing air conditioning or induction cooking, 12V definitely seems to be the move for most folks.
Thanks for sharing, will look into these combo systems!