Quick answer: start with 1,200 W of solar
This is the smallest air conditioner that solar handles comfortably. At about 500 W with the compressor running and 65% on-time over 8 hours, it uses about 2,600 Wh a day, roughly 1,200 W of solar. Cooling demand peaks on the sunniest afternoons, so much of that energy can come straight from the array.
Planning result
At 200 W per module, the array target is 6 panels. That count assumes four peak-sun-hours, 75% end-to-end solar yield, 90% conversion efficiency, and a 20% planning margin. Unlike heating, cooling lines up with solar output: the hottest days are usually the sunniest, so an array sized for the summer design day is working hardest when you need it.
How a 5000 BTU air conditioner actually uses power
Planning case: a 5,000 BTU/h window air conditioner, the smallest common size and normally on an ordinary 120 V outlet, drawing about 500 W while its compressor runs and cycling on its thermostat about 65% of 8 cooling hours. GE rates its 5,000 BTU/h AHEC05AC at 455 W and 4.1 A at 115 V, so 500 W leaves a little margin for less efficient units.
A fixed-speed window unit runs its compressor at full power until the room reaches the set point, then stops the compressor while the fan keeps running or stops. On-time depends on the outdoor temperature, sun on the room, and how well it is sealed: a small, shaded, insulated room can run well below the planning duty factor, while a sun-baked shed can run near 100%.
Load calculation from running watts and duty cycle
The appliance-class estimate is 500 W running for 8 h/day at a 65% duty cycle, an average of about 325 W across those hours:
Then losses and reserve raise the energy the system must collect to about 3,467 Wh/day.
Typical manufacturer EnergyGuide/nameplate/manual range for the 5000 BTU air conditioner class, triangulated with GE Appliances: AHEC05AC 5,000 BTU window air conditioner specifications and GE Appliances: Room air conditioners owner's manual 49-7389, then reduced to a conservative planning midpoint; this is not a product specification. Verify the exact unit's EnergyGuide label, nameplate, and manual before sizing.
Measure on a hot day with a plug-in energy meter for a full day, not a single reading; the compressor cycles, and the daily watt-hours are what size the array.
Solar and battery sizing table
| Design item | Planning value | Basis |
|---|---|---|
| Appliance energy | 2,600 Wh/day | Running W × hours × duty cycle |
| Solar collection target | 1,200 W | 4 peak-sun-hours, 75% yield, 20% margin |
| 200 W panel count | 6 | Rounded up; real modules must satisfy controller voltage/current limits |
| One-day battery allowance | 4,400 Wh | 90% conversion efficiency, 80% LiFePO4 usable fraction, 20% margin |
| 12.8 V LiFePO4 equivalent | 345 Ah | Nominal planning conversion |
| 25.6 V LiFePO4 equivalent | 175 Ah | Nominal planning conversion |
If you only need cooling while the sun is up, much of the load can run from the array with a smaller battery. Overnight cooling for sleeping is what pushes the battery toward the one-day figure.
Build the closest passing wiring-diagram preset
The 5000 BTU Air Conditioner Planning System preset is an engine-passing starting point whose array, battery bank, continuous inverter rating, and surge rating each meet or exceed this page's stated planning allowances. Adjust it only from measured load data and verified equipment limits.
Inverter and startup current
Use at least 700 W continuous with 1,700 W surge for this planning case. The compressor start is the hard part: for a fraction of a second it can draw several times its running watts, and every thermostat cycle repeats it. A soft starter or an inverter-compressor model lowers that peak.
The 1,500 W startup estimate is not a substitute for the manual's locked-rotor, compressor-start, or motor-start requirements, and an inverter's surge rating usually lasts seconds, not minutes. A battery-to-inverter cable that is too long or too small can pull the DC input below the inverter's low-voltage threshold during that start even when the battery has plenty of energy, so use the diagram machine's real run length.
The common mistake
Ways to cut the load
- Shade the window and the outside of the unit; less sun on the room means a shorter compressor on-time.
- Seal the gaps around the unit with its side panels and foam strip.
- Pre-cool the room in the afternoon while the array is producing, then let the thermostat coast into the evening.
- If you are buying new, compare the efficiency rating on the label; a more efficient unit cuts both the watts and the watt-hours.
- After the inverter shuts down or power returns, wait before restarting: GE's manual says to wait three minutes so the compressor overload does not trip.
What to verify before buying equipment
- The exact running watts, startup current, voltage, frequency, and required circuit from the appliance label and manual.
- Actual watt-hours over a representative day; seasonal heating or cooling loads need a design-day measurement.
- Local peak-sun-hours for the worst operating season, plus shade and array orientation.
- Controller maximum input voltage at the coldest expected temperature and maximum output current.
- Battery discharge current, series/parallel permission, terminal torque, low-temperature controls, and overcurrent protection.
- Conductor ampacity, voltage drop, terminal temperature ratings, disconnecting means, grounding, local amendments, and inspection requirements.
For a whole-system load list, use the load and appliance calculator. For the system context around this appliance, continue to the Off-grid heating and cooling guide.
Frequently asked questions
How much solar do I need for a 5000 BTU air conditioner?
For the planning case on this page (a 5,000 BTU/h window unit cooling one small room for eight hours), allow about 1,200 watts of solar at four peak-sun-hours per day. That covers an estimated 2,600 Wh daily load plus conversion, temperature, and recharge margin. If cooling is only needed in daylight, the array can serve much of the load directly.
What size inverter should I use for a 5000 BTU air conditioner?
Plan on at least 700 W continuous and 1,700 W surge. The brief compressor start is the peak to plan for; check the unit manual and the inverter's surge duration, or add a soft starter.
What battery size keeps a 5000 BTU air conditioner running for one day?
The one-day planning allowance is about 4,400 Wh nominal usable design capacity, roughly 345 Ah at 12.8 V or 175 Ah at 25.6 V for LiFePO4. Cooling only during sun-hours needs much less storage; overnight cooling is what drives the battery size.