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Words of Wisdom: “It's not a lost cause.. we just seem to be at that frustrating cusp where it's technically possible with current technology, just not easy or cheap.” – thatswhatsup1)

Running AC on [an inverter] is rich man's game – HaldorEE2)

Running A/C off solar

TL;DR - It is technically possible, but very expensive and complex. Be prepared to spend at least $5,000, and probably closer to $10,000.

More expensive than the A/C system itself is everything you'll need to power it. A/C takes a huge amount of electricity; to operate successfully off grid you'll want at least 8-12KwHr of lithium batteries, 800-1200w of solar, and the required massive charge controllers to run it all. If you want to run the A/C overnight, be prepared to double that battery bank size.

If you are reading this you probably haven't done the math. Prepare for some unpleasant news, because at this point you may not be familiar with:

  • How much power it takes to run the A/C unit continuously
    • Even the most efficient 12v A/C units draw upwards of 60 amps at full blast; that's over 700w, continuous. That will drain even the biggest battery banks extremely quickly.
    • Using a 120v system through an inverter will increase that power draw even more.
  • How much power it takes to start the A/C unit (Usually a lot more)
    • Some units have a “soft start” function, using a bunch of capacitors to help the compressor start while smoothing out the massive spike in current draw
  • How much solar panels are derated in actual use.
    • If it's hot enough to run A/C it's hot enough that you are already losing 25% of your solar panels' rated output due to voltage depression. That is before wiring and charge controller losses.
    • In order to generate 700w of power to run an average system, you'll need at least 1200w worth of panels. And that's just to run the A/C unit itself. That's not giving you any overhead to charge your batteries or do anything else.
  • How much space those panels will require
  • How much money those panels will cost
  • How much money big solar charge controllers cost
  • How much money you will spend on the massive runs of finger-thick copper cabling to connect it all together

And that's just considering running the unit in optimum solar conditions in the daytime. Running A/C at night requires a magnitude increase in battery bank, and then even more panels that are capable of both recharging the batteries while running the A/C during the hotter parts of the day. See this build thread of someone who does.

And it's still not going to give great results; it might be okay for taking the edge off on a very hot day (bringing the inside of the van down to 80f while the exterior temperatures are over 95f), but you're not going to be able to keep the van at 68 degrees on a hot day just off of solar.

Especially because (rather paradoxically) running A/C off of solar requires that you park your van in the sun; which means the inside of the van will get MUCH hotter than it would if you simply parked in the shade. This puts you in a weird catch-22 where you can't run the A/C without parking in the sun, but parking in the sun means you have to run the A/C much harder than your solar can sometimes keep up with.

Running A/C off of shore power

This is very practical, and it's how RVs have been doing it for many years. The A/C systems run natively on 120v AC(Alternating Current) and are getting power from a generator or shore power.

120v AC units are vastly more common, and much cheaper than the 12v or 24v DC units. These are usually roof-mounted, smaller ones can be had for as little as $500 and are very common in the rest of the R/V world. If you have a a big enough inverter, it's possible to run them off of a house battery bank as well (although you'll suffer some efficiency losses).

See this article for a good overview on what may be needed.

But I saw someone on TikTok doing it!

The things you see on social media are either:

  1. Rich people with extremely expensive vans that they paid professionals to build
  2. “Influencers” who spend a weekend or two in the van every month and only post pictures or stories from the most ideal situations
  3. Completely faked and just being shared around to generate views
  4. All of the above.

There is an extremely small subset of people who have successfully installed A/C in their own van, and been able to use it off-grid for extended periods of time. They are people with an in-depth understanding of the issues and the money and space to make it happen. It does not stand to reason that the average person with average resources and commitment will make the trip from idea to implementation.

There is a reason that most people snowbird (follow good weather) and use roof vents to control humidity and temperature.

I am rich, foolheardy, or both, and still want to run A/C off of solar

Don't say we didn't warn you, but here's some links to people who have done it successfully. Start with this post by trebor then check out posts by people who have done it:

Also see

12v/24v/48v DC Units

AC Units that can operate directly on DC current off of your house batteries give some efficiency gains as you don't need to run them through an inverter, but they are very expensive. Higher voltage systems allow you to use much thinner cables for power, which can be a significant cost savings over longer runs.

All-in-one roof units offer a much simpler installation and are usually around $2,500; Dometic has their RTX 2000 unit as a good start for most vans. The relative ease of install comes at the expense of taking up quite a bit of roof space (and consequently reducing your available space for solar panels). They're heavy as well, and generally you'll need to reinforce the roof to hold the weight.

Split units separate the evaporator/condenser/compressor into separate parts which have to be plumbed together. This can offer a lot more flexibility in terms of where to mount stuff, but also makes the installation much more complex. Cruis-n-comfort and UnderMountAC are the two most common split options, and will generally run $4,000 for the units themselves.

Beginning in about 2023, cheap Chinese 12v mini-split systems have started to come down to almost acceptable prices ($1k in the USA, or less if you can wait the 1-2 months for shipping from China). Reports on them have been mixed; similar to the Chinese knock-off diesel heaters they come with almost no instructions and often missing a few minor parts (most users report some fittings or couplings being missing, or needing to crimp their own lines). Warranty and installation support is non-existent, but if you can fiddle your way through the psudo-DIY installation some people have reported positive results.

hvac/solar_ac.txt · Last modified: 2024/02/05 14:25 by princess_fluffypants