Home›Residential Solar›Solar Portable AC Calculator

Solar Portable AC Calculator

Enter your portable AC's BTU and CEER rating — get running watts, solar panels needed, overnight battery size, and a comparison against window AC and mini-split efficiency.

Portable AC settings
CEER
hrs/day
$/kWh
Solar system for your portable AC
3 × 400W panels + 5.0 kWh battery
Running watts (BTU ÷ CEER)500 W
Daily kWh4.00 kWh/day
Monthly kWh120.0 kWh/mo
Annual grid cost$189.80/yr
Annual solar savings$189.80/yr
Battery for overnight5.0 kWh LiFePO4
Est. system cost$8,560
Efficiency ladder — same 5,000 BTU, same hours:
Window AC (~417W)$158.17/yr
Your portable AC (~500W)$189.80/yr
Mini-split (~278W)$105.44/yr
Recommendation: Portable AC → Window AC → Mini-split (most efficient). A mini-split at the same BTU uses ~44% less electricity and needs significantly fewer panels.
Link copied to clipboard

How to Use This Calculator

Select BTU capacity and find your CEER rating

Choose the BTU size of your portable AC. As a rule of thumb, 5,000 BTU covers a 150 sq ft bedroom; 10,000 BTU covers a 300-400 sq ft living space; 14,000 BTU handles a large open-plan room or garage. The CEER (Combined Energy Efficiency Ratio) is printed on the yellow EnergyGuide label on your unit — most portable ACs range from 8 to 12. A higher CEER means fewer panels needed.

Set daily hours and battery preference

Enter how many hours per day the AC runs. For summer bedroom cooling, 8-10 hours is typical. The battery toggle sizes a battery bank for 8 hours of overnight cooling — useful if you want to sleep without the noise of a generator and without drawing from the grid at night. Without battery, the system offsets your daytime and on-bill usage but the AC draws grid power at night.

Read the efficiency comparison

The results show an efficiency ladder comparing your portable AC to a window AC and a mini-split at the same BTU capacity. This helps you evaluate whether upgrading your AC type would reduce both your electricity bill and the solar system size required to offset it.

The Formula

Running Watts = BTU ÷ CEER Daily kWh = Running Watts × Daily Hours ÷ 1000 Annual kWh = Daily kWh × 365 Annual Cost = Annual kWh × Electricity Rate System Watts = Daily kWh × 1000 ÷ Peak Sun Hours ÷ 0.80 Panels = System Watts ÷ 400W (round up) Battery kWh (overnight) = Running Watts × 8 hrs ÷ 1000 ÷ 0.80 DoD Window AC Watts = BTU ÷ (CEER × 1.2) [~20% more efficient] Mini-split Watts = BTU ÷ (CEER × 1.8) [~80% more efficient]

The CEER formula converts BTU/hr cooling capacity to running watts. A 10,000 BTU unit with CEER 10 draws exactly 1,000W. With CEER 12 (a better unit) the same 10,000 BTU draws only 833W — 167W less — saving 14% on panels and electricity. The efficiency comparison assumes window ACs average 1.2× the CEER of portable ACs, and mini-splits average 1.8× (this varies by model — mini-splits with 20+ SEER are dramatically more efficient).

Example

Marcus — Bedroom cooling in Dallas with overnight battery

Marcus wants to cool his bedroom (5,000 BTU portable AC, CEER 10) in Dallas all night. He wants solar to cover daytime use and a battery for 8 hours overnight. He pays $0.13/kWh.

AC5,000 BTU portable, CEER 10
Running watts5000 ÷ 10 = 500W
Daily hours8 hrs (daytime + evening)
Overnight batteryYes — 8 hrs night operation
LocationDallas, TX (5.4 PSH)
Rate$0.13/kWh

Result

Daily kWh4.0 kWh/day
Annual kWh1,460 kWh/yr
Annual cost$189.80/yr
Panels needed2 × 400W panels
Battery for overnight5.0 kWh LiFePO4
Est. system cost~$6,240
Mini-split comparison~$105/yr — saves $85/yr

Marcus's system costs ~$6,240 — a 33-year payback on $190/yr savings, which only makes sense if he already has solar for other loads and this is incremental. However, if he upgraded to a mini-split first (saves $85/yr) and then added 1 panel, his payback drops significantly. The efficiency ladder shows why upgrading the AC itself often has a better ROI than adding solar panels to offset an inefficient unit.

FAQ

Most portable ACs need 1-4 solar panels (400W each) to offset their annual energy use. A 5,000 BTU unit with CEER 10 (500W) running 8 hours/day needs about 2 panels. A 14,000 BTU unit with CEER 8 (1,750W) running 8 hours/day needs 5-7 panels. Keep in mind that panels offset energy over the full day, not instantaneously — a 500W AC drawing power requires either grid-tie or battery storage since a single 400W panel can't run it directly on its own output.
To run a portable AC directly from solar (without the grid), you need a solar array that matches or exceeds the AC's wattage plus an inverter. A 5,000 BTU CEER-10 AC drawing 500W can run directly from 2 × 400W panels during peak sun hours. However, AC units have large startup surge currents (2-3× running watts) so your inverter must handle the surge. Most practical off-grid solar AC setups use batteries to buffer the startup surge and smooth out clouds.
For portable ACs, a CEER of 10-12 is good; 12+ is excellent. The DOE minimum for portable ACs is around 8 CEER. For context, window ACs typically achieve 12-15 CEER and mini-splits achieve 15-25+ CEER (measured as SEER on mini-splits). If your portable AC has a CEER below 9, upgrading to a window AC (if your space allows) provides better efficiency with less solar required. The CEER rating is on the yellow EnergyGuide label — required on all new AC units sold in the US.
Almost always yes if you're installing solar. A mini-split at the same BTU uses roughly 40-55% less electricity than a portable AC due to its much higher efficiency. This means fewer solar panels, smaller batteries, and lower ongoing costs. The tradeoff: mini-splits cost $1,500-4,000 installed vs $300-700 for a portable AC. However, the energy savings ($100-400/yr depending on usage) typically pay back the cost difference in 3-8 years — and you'd need that much less solar capacity anyway. For solar-powered homes, the efficiency ladder matters: design your appliances for efficiency first, then size the solar to match.
Battery size for overnight AC cooling depends on AC wattage and hours needed. Formula: Running Watts × Night Hours ÷ 1000 ÷ 0.80 DoD. Examples for 8 hours of overnight cooling: 5,000 BTU (500W) needs 5 kWh; 10,000 BTU (1,000W) needs 10 kWh; 14,000 BTU (1,750W) needs 17.5 kWh. These are substantial battery banks. At $800/kWh for LiFePO4, a 10 kWh battery costs $8,000 — often more than the AC unit. For overnight cooling, running a small window AC (lower wattage, higher CEER) dramatically reduces the battery size needed.

Related Calculators

❄ Air Conditioner Solar Calculator
Size solar for central AC, window units, and mini-splits.
🔋 Battery Bank Calculator
Calculate battery Ah for overnight or multi-day loads.
☀ Solar Panel Calculator
Size a complete home solar system including all appliances.
⚡ Power Consumption Calculator
Add all your appliances and get total daily kWh and panel count.

Embed This Calculator

Free to embed on your website. Just copy this code:

<iframe src="https://solarsizecalculator.com/solar-portable-ac-calculator"
  width="100%" height="620" frameborder="0"
  title="Solar Portable AC Calculator"></iframe>