Two hours AC

Project_Mayhem · Tuesday at 11:19 AM

Are you using an inverter? How old is the AC unit?

Tally Ho · Tuesday at 12:31 PM

patrickfarley said:
I plan to put a 5000 btu AC in the V berth with a vent system to the forward hatch. The AC will drain into the bilge and pump out with the bilge pump. It will run off a battery system that has 1024AH.

It should last more than two hours. That is enough time to set up the sails and get moving in the wind or find a place to swim.
I grew up on a ranch/farm in the central valley of California. Heat does not bother me but I like to sail with my wife. Two hours should do the job. I also have solar panels and can recharge when stopped. I can charge a little while moving but not enough to keep it running.

Are you planning on sailing with the A/C on? Or use it at anchor?

Usually when sailing, as long as there is a breeze, the heat is tolerable. At anchor, with no breeze, particularly if trying to sleep can be tough. I use some 12-volt fans by Caframo that help a lot in the cabin. My biggest issue with heat is at the dock, where the wind is blocked….

I tried a window unit at first, mounted in my companionway and surrounded with some foam board to block out the warm air. It was a 5000 btu unit. I ran it off shore power only. Condensation dripped in the cockpit and out as upper drain. But it didn’t really keep my boat very cool. I have a 32 foot O’Day 322, so a bit more to cool than your 25. It also had to be removed when sailing and I had to climb over it when it was in place at the marina.

Last year, I bought one of those free-standing units with the hose to push the hot air out of the boat. It was 8,000 BTU. It drains into my bilge. The biggest issue with this unit is the size and where to run the exhaust hose. And the thin vinyl hose itself puts off a lot of heat. I found a place for it, routed the house out of a portlight that opens to my cockpit, and then insulated the hose with Reflexite. Made it more efficient and made staying at the dock almost tolerable. Except the thing blocked access to the rear berth.

I don’t have any photos of the free-standing one I guess.

1024 Ah on a 25 foot boat seems like a lot. Is it LiFePO4?

Davidasailor26 · Tuesday at 6:49 PM

patrickfarley said:
I am using a portable power station. I may get the one with 1500AH.

Most portable power stations are measured in watt hours, not amp hours. The biggest Jackery I can find, for example, is 5000 watt hours. It looks like that could fit on a boat, being about suitcase sized, but it’s also $3000. At 110 volts the 1500 watt hours unit is about 13 amp hours. For a 5000 btu AC I guess that could be a couple hours runtime.

patrickfarley said:
700watts of solar

That’s probably about 33 square feet of solar panels. Not exactly easy to transport and deploy.

Davidasailor26 · Tuesday at 6:58 PM

By the way, the rule of thumb is that solar panels can output about 3-4 times their hourly rating in a day. Since you’re probably using the AC on hot sunny days you could maybe bump that up to expect 5 times. So to sustain a 1500 watt hours per day draw would be maybe 300 watts of solar. That’s about 14 square feet of panels, which is more achievable but probably still challenging with a 25’ boat.

dlochner · Tuesday at 7:07 PM

One issue with any electric motor is the inrush current. The power station may have enough power to run the AC, however is it able to deliver enough power to get the compressor motor to start? There are soft start devices that can help over come this issue, unfortunately I can't give you more advice than that.

Davidasailor26 said:
By the way, the rule of thumb is that solar panels can output about 3-4 times their hourly rating in a day. Since you’re probably using the AC on hot sunny days you could maybe bump that up to expect 5 times. So to sustain a 1500 watt hours per day draw would be maybe 300 watts of solar. That’s about 14 square feet of panels, which is more achievable but probably still challenging with a 25’ boat.

In 2 years of live aboard sailing along the east coast including souther states, the best my 300 watts of solar ever did was about 1400 wh. On most sunny days I would get between 1K and 1.2K wh. Solar Panel output on a boat is not at all stable. Not only are clouds passing over head, the boat is constantly moving causing the sun angle to change and shadows to go across the panel from the rigging and sails.

Tally Ho · Tuesday at 7:27 PM

patrickfarley said:
Main idea is to make a cool area for my wife.

Put her at the helm, under a Bimini, or let her have a swim! Anywhere but in the cabin!

Greg

Project_Mayhem · Tuesday at 8:05 PM

Don't forget about inverter efficiency. It can vary from model to model and how high the load is. The better manufacturers publish charts that tell you how efficient it is at a given load

SteveHughessails · 2026-01-14T08:20:28-0800

I built myself a solar generator last year with a Lithium iron 100Ah battery. I’ve been having fun, long story short, we boil water with propane. Running a window A/C, never even considered it. We can, if we have to, boil water now with 300 watts and 15 minutes. Low power use utilizing a rice cooker/steamer. (Genius)

I’m looking at 2 window A/C’s on my floor lol. (We’re painting) hmmmm. I have a victron shunt litime 100Ah Lifepo4 and a 12volt 1500 watt inverter. Solar charging with MPPT and 2x 100 watt BB16 panels. We constantly see just over a 5 Amp charge.

The small A/C on top is 5200 BTU. I will hook it up, let’s see what it pulls.

dlochner · 2026-01-14T08:36:50-0800

There isn't enough power to run an AC. The 100ah LFP battery has 1200wh plus the 5a solar is 1260 wh. The 1500 watt inverter will drain the battery in about 45 minutes running full bore assuming the battery is fully charged and no other devices are using the battery. If the unit you are looking at is like this one from Amazon, it seems to draw 1500 w. This is not accounting for inverter inefficiencies and assuming the battery can supply enough power to start the unit.

SteveHughessails · 2026-01-14T09:48:53-0800

Here are the results. A/C 5200 BTU window unit, powering up and running the air conditioner it consumes a steady 6.72 Amps. Once the compressor kicks in, 32 Amp constant draw reporting just under 4 hours runtime.
I would imagine that would drop quickly too. I did not run it for very long.

I felt the inverter was over worked running this. I would be concerned about it’s lifespan if asked to run this regularly. If it was me, no to the 1500 watt 12volt inverter. 300Ah Watts cycle Lifep04 batteries x2 for 24 volts (they are tested to be ok and very inexpensive) and a 3000 watt plus inverter would be a useful test.

Failing that, pull a gas generator behind you.

kloudie1 · 2026-01-14T20:14:02-0800

Check out a split 12 v system with a 12v electric compressor. Ya have the problem of where/how to put the condenser (the hot side) but in the kit is enough refrigerant hose to let you work it out.

Amazon.com

Project_Mayhem · 2026-01-15T08:33:40-0800

Have you tried a 12v fan? They're around $20 on amazon

Model	E1500LFP
Rated Power	2200W
Peak Power	4400W (10ms)
Capacity	1536Wh
Output Volts	100V~120V Pure Sine Wave
Dimension	14.8x9.4x12in
Battery Type	LiFePo4
Weight	40lbs(18.2Kg)
DC Output	30A(12V)
Solar Input	DC5521: Voc 12V~18V / 100W Max /7A Max GX16MF: Voc 32V~95V / 700W Max / 15A Max
Car Input	DC 12V~18V-100W Max
AC Input	100V~120V/ 1400W
Charging Time	1.8 Hours
Smart APP	APP Control. Wifi / Bluetooth control;
Charge Temperature	0°C~45°C / 32°F-113°F
Discharge Temperature	-20°C~45°C / -4°F-113°F

Model	E1500LFP
Rated Power	2200W
Peak Power	4400W (10ms)
Capacity	1536Wh
Output Volts	100V~120V Pure Sine Wave
Dimension	14.8x9.4x12in
Battery Type	LiFePo4
Weight	40lbs(18.2Kg)
DC Output	30A(12V)
Solar Input	DC5521: Voc 12V~18V / 100W Max /7A Max GX16MF: Voc 32V~95V / 700W Max / 15A Max
Car Input	DC 12V~18V-100W Max
AC Input	100V~120V/ 1400W
Charging Time	1.8 Hours
Smart APP	APP Control. Wifi / Bluetooth control;
Charge Temperature	0°C~45°C / 32°F-113°F
Discharge Temperature	-20°C~45°C / -4°F-113°F