Can you run an RV air conditioner on solar?

The honest answer: for a few hours on a sunny summer day, yes, with a large lithium bank, a 2,000 W inverter, a soft starter and roughly 800 W of panels. All day and through the night, on solar alone, it is usually not practical for an RV or van. Here are the numbers, from the same calculator and NASA sun data as the rest of RVWatt.

What one air conditioner uses

The RVWatt library models a 13.5k BTU rooftop air conditioner with a soft starter at 1,300 W running, 80% of the time it is on, for 3 hours a day. That is 1,300 × 3 × 0.8 = 3,120 Wh at the unit. Through a 90% efficient inverter it takes about 3,467 Wh from the battery, and the inverter’s idle draw adds about 30 Wh more, for a total of about 3,497 Wh a day.

For comparison, the entire weekender van preset, with a 12 V fridge, fan, lights, pump and phones, uses 830 Wh a day. Three hours of air conditioning is more than four times everything else in that van combined. Larger 15k BTU units and older units without a soft starter usually draw more; check your unit’s label.

How big the system gets

These results are for the air conditioner alone, at 12 V with LiFePO4 and the calculator’s default two days of reserve, unless noted. July is used because it is the month people most want cooling and one of the sunniest.

Case	Daily use	Solar needed	Array	LiFePO4 bank at 12 V
Phoenix, AZ, July, 1 hour a day	1,166 Wh	206 W	2 × 200 W (400 W)	243 Ah (2.9 kWh)
Phoenix, AZ, July, 3 hours a day	3,497 Wh	617 W	4 × 200 W (800 W)	728 Ah (8.7 kWh)
Phoenix, AZ, July, 3 hours, one day of reserve	3,497 Wh	617 W	4 × 200 W (800 W)	364 Ah (4.4 kWh)
Denver, CO, July, 3 hours a day	3,497 Wh	660 W	4 × 200 W (800 W)	728 Ah (8.7 kWh)
Phoenix, AZ, June–August, 3 hours a day	3,497 Wh	669 W	4 × 200 W (800 W)	728 Ah (8.7 kWh)
Phoenix, AZ, July, 3 hours plus the weekender van loads	4,327 Wh	763 W	4 × 200 W (800 W)	901 Ah (10.8 kWh)
Phoenix, AZ, July, 8 hours a day	9,324 Wh	1,645 W	9 × 200 W (1,800 W)	1,943 Ah (23.3 kWh)

Three hours a day is possible on paper: about 800 W of panels and a large lithium bank, in a sunny month. A day of reserve is a reasonable choice for air conditioning, because you would not run it on solar through a cloudy spell; that halves the bank to about 364 Ah. Eight hours a day is another story. It needs about 1,800 W of panels, more than most RV roofs can hold once the air conditioner, vents and antennas take their space, and the calculator warns about roof space. Running it overnight means all of that energy has to come from the battery.

Open the air conditioner in Phoenix, July Same, one day of reserve Add it to the weekender van loads

Why real life is usually harder than the table

The table is a best case in several ways. In a desert July afternoon an air conditioner can run nearly nonstop, not 80% of the time. Roof panels get very hot, so the default 10% heat loss is optimistic in Phoenix; raise it in the calculator’s advanced settings and watch the array grow. The hottest hours are mid-to-late afternoon and evening, when panels are past their best, so the battery does most of the work. And an uninsulated rig with big windows in full sun needs far more cooling than a shaded, well-insulated one.

The math also uses monthly averages. One hazy or stormy day and the bank does not refill. That is fine for lights and a fridge with two days of reserve; it is a much bigger hole when one day of cooling uses 3.5 kWh or more.

The inverter, soft starter and battery

The calculator sizes a 2,000 W inverter for this unit (1,300 W × 1.25 ≈ 1,625 W, rounded up) and expects start-up surge around 3,250 W, which assumes a soft starter. Without one, the start-up surge of a rooftop compressor is often high enough to trip a 2,000 W inverter. At 12 V the unit draws roughly 120–140 A while running, and a 2,000 W inverter can pull about 212 A at full output, which needs a 300 A fuse and 3/0 cable at a short run. At 48 V the same inverter draws about 53 A on a 70 A fuse and 8 AWG cable, one reason larger air-conditioning systems often use 48 V. See what size inverter for an RV for the full table.

This is a lithium job. With AGM at 50% usable, the same 3-hour, two-day case needs about 1,166 Ah at 12 V, and AGM handles the high current far less comfortably. See LiFePO4 vs AGM.

What usually works better

Run the air conditioner on shore power or a generator, and let solar cover everything else.
Use solar plus a large lithium bank for a short, planned window, such as cooling the rig for an hour or two before bed, rather than all afternoon.
Add alternator charging through a DC-DC charger if you drive most days; enter the amps and hours in the calculator and it subtracts that energy before sizing solar.
Cut the cooling load: shade the windshield and windows, ventilate with roof fans in the morning and evening, and park with the big windows away from the afternoon sun.
Travel where the weather is milder. The peak sun hours guide shows the sun side; higher elevations are often cooler in summer.

Some factory and aftermarket packages advertise off-grid air conditioning. When they deliver it, they do it with a very large lithium bank and a second alternator or a generator, not with a few hundred watts of roof solar alone.

Safety

An air-conditioning system on batteries combines the highest DC currents in an RV with 120 V AC wiring. Install a soft starter according to the air conditioner maker’s instructions, and check whether it affects your warranty. Connecting an inverter to the RV’s 120 V panel needs a transfer switch so shore power, a generator and the inverter can never feed the same circuit together. Have a qualified RV electrician or licensed electrician do or check that work.

Frequently asked questions

Can you run an RV air conditioner on solar power alone?

For a few hours on a sunny summer day, yes, with a large system. A 13.5k BTU unit with a soft starter running 3 hours a day uses about 3,497 Wh from the battery. In Phoenix in July that needs about 617 W of solar, so roughly 800 W of panels, and about 728 Ah of 12 V lithium for two days, or about 364 Ah for one. All day and through the night on solar alone is not practical for most RVs.

How many solar panels does it take to run an RV air conditioner?

About four 200 W panels for 3 hours a day in a sunny July, using the calculator’s defaults. For 8 hours a day it is about 1,800 W, nine 200 W panels, which is more than most RV roofs can hold. Those figures assume a soft starter and do not include anything else in the rig.

What size inverter do I need for an RV air conditioner?

For a 13.5k BTU unit at about 1,300 W running, RVWatt suggests a 2,000 W pure sine inverter and a soft starter, with a surge rating around 3,250 W. Without a soft starter the start-up surge can trip the inverter. At 12 V a 2,000 W inverter needs a 300 A fuse and heavy 3/0 cable at a short run.

Do I still need a generator for air conditioning?

For most RVers who want air conditioning for more than a few hours a day, yes, or shore power. A practical plan is to run the air conditioner on a generator or shore power and use solar and lithium batteries for everything else, or for a short, planned cooling window.

Related guides

Safety: high-current DC is dangerous. A 12 V battery bank can deliver thousands of amps into a short circuit, enough to melt tools, weld rings and watches to terminals, ignite insulation and start a vehicle fire in seconds. Lithium and lead-acid batteries can also vent, burn or explode if overcharged, damaged or charged outside their temperature limits. Remove jewelry, use insulated tools, disconnect the battery before working, fuse every positive conductor as close to the battery as practical with a fuse rated for the battery's short-circuit current (often a Class T for lithium banks), use properly crimped lugs and pure copper cable, and secure batteries against movement. If you are not confident, hire a qualified RV or marine electrician. RVWatt provides estimates only; see our Terms of Use.

These figures are planning estimates from typical appliance ratings and NASA monthly sun averages for a flat, horizontal panel. Your real use will differ with heat, shade, dirty panels and how you actually live in the rig. Follow your equipment manuals and have a qualified installer check high-current wiring.