5000 btu ac on solar

Do you have the window unit already? Can you run it on a Kill-a-Watt type meter from utilty power or a genset for a day or two get get a rough idea of the energy usage?

Using an LG 14,000 BTU Inverter based window unit from Homedepot:

https://www.homedepot.com/p/LG-Electronics-14-000-BTU-115-Volt-Dual-Inverter-Smart-Window-Air-Conditioner-in-White-with-Wi-Fi-Enabled-and-Remote-LW1517IVSM/303947186
https://images.homedepot-static.com/catalog/pdfImages/03/037856e8-8b1a-49d7-a73a-32b23333dc55.pdf

Converting from the Energy Star Tag (they don't make it easy)... $68 per 3 months @ 8 hours per day @ $0.13 per kWH (that is 1/2 to 1/3 my California costs--Ugh).

• $68 per season * 1/$0.13 per kWH * 1/8 hours per day * 1/3 months * 1/30 days per month = 0.726 kWatts = 726 Watt load (sounds reasonable)

http://www.solarelectricityhandbook.com/solar-irradiance.html

Spartanburg SC
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 70° angle from vertical:
(Optimal summer settings)

Jan	Feb	Mar	Apr	May	Jun
3.34	3.80	4.83	5.66	5.85	5.72
Jul	Aug	Sep	Oct	Nov	Dec
5.63	5.27	4.85	4.63	3.66	3.22

If you want to run only (or mostly) under direct sun, assume 50% of array capacity, or:

• 726 Watts * 1/0.77 panel+controller derating * 1/0.50 use of output in less sun * 1/0.85 AC inverter eff = 2,218 Watt array "nominal"

If you base this off of running from the battery bank or panels from March through September, then:

• 726 Watts * 6 hours per day = 4,356 Watt*hours per day
• 4,356 WH per day * 0.52 off grid system eff * 1/4.83 hours of sun per day (March average) = 1,734 Watt "March break even" array

Battery bank is a bit more iffy... Assuming the LG draws no more than 726 Watts (inverter based A/C), and assuming a 24 volt FLA (flooded lead acid battery bank) will support ~500 Watts per 100 AH @ 24 volt running load:

• 726 Watts * 100 AH (per 24 volts) * 1/500 Watts (per 100ah) = 145 AH @ 24 volts minimum FLA battery bank

That way, the Window AC should always start (even if a cloud goes by). But you would not be using more than an 1 or 2 of battery runtime per day on such a small bank--Rely on the Solar panels and full sun most of the time.

If you are running in Afternoons, you might want to think about pointing the array more South West (more energy direct from array in afternoons).

My guess (purely SWAG) would be 4x 6 volt @ 200 AH "golf cart" batteries in series for a 24 volt @ 200 AH battery bank. And somewhere around a 1,734 to 2,218 Watt array minimum.

If you go with a south west array, then the solar numbers look like (note: I tilted the panels a bit more for afternoon harvest in spring/fall--This does "kill" the mid day harvest a fair amount:

Spartanburg
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 55° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
3.58	3.89	4.72	5.23	5.20	5.01
Jul	Aug	Sep	Oct	Nov	Dec
4.96	4.79	4.64	4.71	3.90	3.52

How you run the window AC will also affect usage... Dave A. here (as I recall) starts the system earlier in the day, on low, to pre-cool the room and then let the system "run on low" through the hot afternoons... Vs just turning on full at 12 noon.

Note that A/C systems do use a lot of energy per day (2x that of an full size energy start refrigerator). So, this is not going to be a "small/cheap" system.

Anyway, a SWAGs (scientific wild ass guess)... Are they of any help?

-Bill