GetWattLogic

"Can I run an air conditioner on solar?" is the question every van and tiny-house owner eventually asks — usually in July, staring at a 1,000W rooftop AC unit and a 400W solar array. The honest answer is: yes, but it's the most expensive single load you can put on an off-grid system, and most people who try it end up disappointed.

Here's the real sizing math and the four ways people actually make it work.

Why AC is the hardest load in off-grid solar

A typical small RV or van air conditioner draws:

• Running draw: 800–1,500W (depending on size)
• Surge / startup draw: 2,500–4,500W for 1–3 seconds (compressor starting)
• Daily energy (8 hours of run time): 6–12 kWh

Compare that to a fridge (~580 Wh/day) or LED lights (~200 Wh/day). A single hour of AC uses more energy than two days of fridge and lights combined. This is the fundamental problem: solar scales with panel area, and AC demand is enormous.

The math: how much solar to run AC

Using the formula from our solar sizing cheat sheet:

Panel watts = (Daily Wh ÷ Peak sun hours) ÷ 0.7

For a small 1,000W AC running 6 hours/day (6 kWh/day) in a 5-peak-sun-hour summer climate:

6,000 ÷ 5 ÷ 0.7 = ~1,700W of panels just for the AC

For a 13,500 BTU RV rooftop AC running 8 hours/day (10.4 kWh/day):

10,400 ÷ 5 ÷ 0.7 = ~3,000W of panels just for the AC

And this is summer sizing. Most vans can fit 600–800W on the roof. You can see the problem.

The battery problem

Running AC at night is the real killer. If you want to run AC overnight without a generator, your battery has to store the full nightly draw:

• 6 hours of AC overnight = 6–9 kWh of usable storage
• That's a 500–700Ah 12V LiFePO4 battery — physically large and $2,000–4,000 just for the battery

Most van builds have 200–400Ah of battery. That gives you 2–4 hours of AC, not a full night. This is why almost no van runs AC overnight on solar alone.

The four real ways people make AC on solar work

1. Run AC only during peak solar hours (the most common approach)

If your panels can produce 1,500W+ at noon and your AC draws 1,000W, you can run the AC directly off solar during peak hours without touching the battery. This is the cheapest setup. Drawback: AC only works when the sun is strongest, which is exactly when you need it least (you need AC at night, not noon).

2. Oversize everything (the expensive approach)

~3,000W of panels, 600Ah+ of LiFePO4, a 3,000W+ inverter. This works — people do it — but it's a $8,000–15,000 system for AC alone, and the roof space required is beyond most vans. Realistic for large Class A RVs and stationary tiny houses, not vans.

3. Use a DC-powered, high-efficiency AC (the smart approach)

Traditional RV rooftop ACs are 120V compressor units with terrible efficiency. Newer 12V/24V DC air conditioners (like the Nomadic Cooling, Dometic RTX, or Indel B) draw half the energy — ~400–600W running instead of 1,000–1,500W. This shrinks the entire system: a 1,000W array and 300Ah battery can actually run a DC AC for several hours.

Drawback: DC AC units cost $1,500–3,000 (vs $600–1,000 for a standard RV AC). You're paying upfront for efficiency.

4. Hybrid: solar + generator + small battery (the pragmatic approach)

This is what most full-time van dwellers actually do:

• Solar handles the daytime loads (fridge, lights, laptop, fan)
• A small inverter generator (2,000W Honda or champion) runs the AC for the 2–3 hours a night you really need it
• The battery bridges the gap and handles everything except AC

A $1,000 generator + $100 of fuel/month is dramatically cheaper than the $8,000+ system to run AC on solar alone. See our propane vs gasoline vs diesel generator guide for the generator side.

The inverter requirement

Whatever path you choose, the inverter must handle the surge, not just the running load. A 1,000W AC has a startup surge of 2,500–3,500W for the compressor's first 1–3 seconds. A 1,500W inverter will trip on the surge every time.

• Pure sine wave — non-negotiable for a compressor, same as for a fridge
• Continuous rating ≥ AC running watts × 1.5 (for headroom and hot-weather derating)
• Surge rating ≥ AC surge (check the AC's locked-rotor amps × 120V)

For a 1,000W AC, you want a 2,000–3,000W pure sine inverter with a 4,000W+ surge rating. See our inverter sizing guide.

A realistic "yes, you can" system

For a van that wants to run a 12V DC high-efficiency AC (~500W) for 4 hours/day in summer:

• Panels: 800W on the roof (4 hours × 800W × 0.7 = ~2,240 Wh — enough for the 2,000 Wh AC draw + basics)
• Battery: 300Ah LiFePO4 (~3,200 Wh usable — runs the AC for 4 hours from battery alone if needed, plus bridges cloudy spells)
• Inverter: 2,000W pure sine (for the DC AC's surge + other loads)
• DC AC unit: 12V or 24V high-efficiency model
• Total cost: ~$5,000–7,000

This works. It's not cheap, but it's achievable. The same load on a standard 120V rooftop AC would need double the panels and battery — pushing $12,000+.

The honest summary

• Running AC during peak sun only: feasible with ~1,500W of panels, no big battery needed
• Running AC overnight on solar: requires a massive, expensive battery — usually impractical
• The smart money: a high-efficiency 12V/24V DC AC unit halves your system cost
• The pragmatic money: a small generator for the 2–3 hours a night you actually need AC, with solar for everything else

Before you commit, run your full load profile (including the AC) through the GetWattLogic calculator — it'll show you the panel, battery, and inverter size that AC forces on the system, and you can decide if the cost is worth it. For high-efficiency DC AC units and the batteries that run them, see the Recommended Gear page.