Can You Run a Marine Air-Conditioner on Battery Power?

Is untethered comfort at anchor achievable with current technology? We're doing just that. So let’s delve into the upgrades that enabled this, the decisions we made, and how well it actually works.


Our 16,000 BTU MarinAire A/C is sufficient to maintain our Privilege 435 catamaran at under 26.5°C (80°F) on days up to around 35°C (95°F). However, the exact setup may vary based on the size of your boat and preferences.  The challenge is, the units themselves are not cheap, the systems to support them are not cheap, and the labor to install everything can be extensive. So, we need careful system planning to get it right on the first try.

To continue reading this article or issue you must be a paid subscriber.

Subscribe to Practical Sailor

Get the next year of Practical Sailor for just $34. And access all of our online content - over 4,000 articles - free of charge.
Subscribe today and save 42%. It's like getting 5 months FREE!
Already Subscribed?
| Forgot your password? | Activate Web Access
Adam Morris
A lifelong sailor, Adam Morris spent his formative years sailing dinghies at Raritan Yacht Club in New Jersey, a foundation that paved the way for his current life as a liveaboard on SV Confianza, affectionately known as Connie. He and his co-captain, Angie, embrace the sea full-time, balancing passion for cruising with the demands of working remotely from their floating home. As the voice behind, Adam chronicles their journey through the complexities of upgrading, maintaining, and outfitting Connie for a lifestyle that merges the freedom of the open sea with the necessities of full-time work and living.


  1. Hey Adam, thanks for the very informatve article…

    Namely, it’s spot on to what I’ve been doing since Jan ’23…

    I have the Dometic 16k uses about 1200w overnight for a good 6-8hrs A/C nightly…

    If cloudy for 5-6 days running my 1.8kW bifacial does not keep up otherwise seems adequate…

    I plan to add 2×450/500W bifacial and lower the latitude by 10 degrees in hopes I won’t need more…

    My answer to running marine A/C: definitely…!

    Fair Winds…

  2. Last fall I finally had enough of my loud, high maintenance panda generator. The difficulty for me to maintain the unit in such cramped spaces and the problem finding a mechanic to do it, were the final straws. Over this past winter I went all in on lithium and 12 V air conditioning. I had the Mabru 12K, 12V unit installed in the main cabin along with 660 A of lithium batteries. This first step was intended to provide air to the main salon and forward cabin. I’m still in the testing phase, and if things work out, I will place a 7K unit in the aft cabin. While I have not seen the combination of summer heat and warm water yet, the results are quite promising. In heat mode the unit operates at a maximum 39 A and reduces below 30 when within 2° of set temperature. Cooling mode seems to be slightly less amp draw. During my only big test so far, I dropped anchor and ran the unit for 19 hours straight in heat mode. Outside air temperature was between 45 and 50° with the unit set at 68°. Water temperature was 45-47 degrees. I started at 100% battery and ended, 19 hours later, at 30% battery. I have 900 W of solar and a 170 amp alternator. With a relatively small battery bank of 660 A it is important to have a large solar array. By the time I left the Anchorage, it only took a couple hours for the solar and alternator to power me up to 100% again. Needless to say, I am quite pleased. We shall see how things go in the heat of the summer, but so far I am happy as a clam to be finished with that damned generator. This is not an inexpensive upgrade. So far I’m at 25k. I figure it would probably cost 20k to have a quiet, high-quality northern lights installed. Maybe more. So I’m not too far off the mark and quite pleased with the results so far. Mark Robinson Catalina-Morgan 440, Journey2

  3. Good myth busting.

    I did something similar with my PDQ 32 cat (Dometic Turbo 12,000 BTU) and wrote it up some years ago. Soft start, but not variable speed; as you pointed out, it’s a zero sum game. Interestingly, it is mostly cats that do this. I’m guessing it is related to the convenience of mounting a lot of solar on the hard top.

    You really only need AC at night IME. During the day, if you can’t hack the heat, with a breeze, you aren’t going to enjoy sailing anyway. I would typically get underway early, with the family still asleep, and they appreciated being able to stay cool until we were out in the breeze. Chesapeake coves can get down right steamy at night.