How many batteries / panels do I need to run my air conditioners for 6 hours at night?
The sun has gone done and you might as well be on the moon, fully reliant on your 48 volt off grid battery happily topped off at 52.8 volts. As the night goes on, you watch your voltage drip down to 51.4, 51.2 where it hovers for a while, and then slowly goes below the 50's, where you know you don't have much juice left, as you eagerly await dawn and the fresh energy the sun will bring.
It's an amazing feeling being disconnected from the grid. Harvesting your daily power, day after day, season after soon, diligently putting it away in your LFP battery bank for the night, and enjoying the harvest through the nights.
Being completely off the grid is now a reality. Might as well enjoy it by adding true DC powered air conditioning and heating into the mix to live like a true modern energy-independent human.
My story started with a beautiful 2800 square foot metal shed in the middle of the desert. Lacking connectivity to the power utility, I was completely reliant on solar panels. Luckily in the southwest, we have loads of sun and mostly sunny days year-round. The cost of solar panels being extremely affordable, it was a no brainer to load up on as many kilowatts of power as the roof would hold.
One of the best inverters for people serious about off grid solar power for their home, farm, or business, is the Schneider XW Pro series of inverters. No affiliation -we don't even sell their products - but these inverters do something many Chinese units just can't - deliver massive bursts of power for starting loads (like well pumps, compressors, air conditioners) - run at full power for long periods of time, and scale via daisy chaining as your power demands grow.
A Scnheider 6848 will provide about 6000 kilowatts continuous, which is plenty for a typical household or small business. However, a building typical for this much power consumption, will most likely be in the 1500 - 3000 square foot range, and require an air conditioner in a 3 to 6 ton range. The 5 ton package air conditioner we bought pulled about 4800 watts continuous power when cooling. It was insane. The Scnheider ran on full blast like an angry beetle, driving my efficiency-seeking soul insane.
We soon realized that while solar is great, and household appliances, lights, fridges, and TV's — all play well with a reasonably sized inverter. But the story changes one central air conditioning, or any attempt as serious air conditioning, takes place.
You have to dedicate an inverter for your air conditioning. If it even works.
Our 5 ton A/C ran for 2 months. Then, it died. It died because the inverter did not provide enough amps to start the compressor in the AC, and eventually the compressor fried.
Since then, we switched to pure DC-powered heat pump air conditioners. These air conditioners can be wired in directly to the 48 volt battery system using DC breakers. The solution required absolutely no inverters. All motors and compressors inside the air conditioners use DC permanent magnet motors, which are 30% more efficient than AC induction motors used in traditional AC systems. There is no burst of starting current needed to begin operation. The electrical wiring, being only 48 volts instead of the traditional 220-230V, is a lot safer for the DIY guy or gal to install and maintain. For the nerdy health-conscious, there is no EMF on the lines in the 50-60Hz range as the units are pure DC.
And perhaps most importantly, it is quiet. Inverters are loud! An inverter with a small load (everything except your power tools, electric car, or air conditioners will be low power nowadays) hums along nicely. Add an air conditioner, and the inverter has to run on full power, buzzing, with or without fans, in the annoying 60 Hertz buzz. You wanted off grid to enjoy the serenity of being one with nature - not operating a power plant.