Powering Your Home's Central Air Conditioning with Off-Grid Solar: A luxury or Reality?

The idea of running your central air conditioning entirely on solar power is both exciting and revolutionary. As of now, achieving this dream requires a significant investment, primarily because the technology is still in its nascent stages. While it's feasible, it's currently a luxury that comes with a premium price tag. But here's the silver lining: like all new technologies, as it matures and becomes more widespread, costs will inevitably decrease. RevoPower is at the forefront of this innovation, and we're optimistic that in a few years, this will become a more accessible reality for many. If you're among the early adopters with the means to invest in this sustainable vision, we're here to make it happen. For the rest, hold tight; a more sustainable and affordable future is on the horizon.

Fortunately, if you want to power your central AC with solar: You've come to the right place! RevoPower's Rebel Solar and Wind Generators are the most powerful solar and wind generators on the market. They're up to the challenge and already running homes, workshops and off-grid structures all over the USA.

Central air conditioning is a significant energy consumer in most households. If you're considering powering your AC with off-grid solar, here are some essential factors to keep in mind:

1. Size and SEER Rating of Your AC

The size of your home and the SEER (Seasonal Energy Efficiency Ratio) rating of your AC unit play a pivotal role. The SEER rating indicates the cooling output during a typical cooling-season divided by the total electric energy input. The higher the SEER rating, the more efficient the AC unit.

2. Solar Panel Capacity

Solar panels are rated based on their maximum output under ideal conditions. For instance, a 100W solar panel is tested under laboratory conditions, which means it might not produce a full 100W in real-world scenarios. Factors affecting this include:

• Angle and Orientation: Solar panels produce the most power when the sun is directly overhead. The angle and orientation of the panels can affect their efficiency.
• Temperature: Solar panels tend to be less efficient in very hot conditions.
• Dirt and Debris: Dust, bird droppings, and other debris can reduce the efficiency of solar panels.
• Age of the Panel: Over time, solar panels degrade and produce less power.

Make sure to carefully estimate exactly how many solar panels you need. We usually recommend calculating exactly how many you need and then roughly doubling it. For example, if your air conditioner uses 3,000W and total run time is 5 hours / day, you will need at least 15,000 watt-hours of solar charging. Depending on your area, if you can harvest 4.5 sun-hours, this comes out to 15,000 ÷ 4.5 = 3,333 Watts of solar panel. In this case, we would typically recommend around 6,000W.

Although you can always expand your Rebel’s solar panel input, it can be frustrating to start with not enough solar panels. Depending on your budget though, it can also be beneficial to start small and add them as you go.

If you have existing rooftop solar, it's designed to feed into the grid and might not directly power your home during an outage. Retrofitting these systems for off-grid use involves adding battery storage and possibly changing the inverter setup.

3. Understanding AC Run Time vs. Cycle Time

Air conditioners don't run continuously at their maximum rated power. They cycle on and off based on the thermostat setting and the temperature inside your home.

• Run Time: This is the actual time the AC is running and consuming power. If your thermostat is set to 72°F, the AC might run until the temperature is a degree or two below this, then turn off.
• Cycle Time: This refers to the full duration of an on-off cycle. For instance, if your AC runs for 15 minutes and then turns off for 45 minutes, the cycle time is 60 minutes.

Understanding this difference is crucial when sizing a solar and battery system. You need to account for the AC's maximum power draw during its run time and the total energy consumption over a day.

4. Battery Storage for Off-Grid Solar-Powered AC

Battery storage is the backbone of an off-grid solar system, especially when powering energy-intensive appliances like central air conditioning. Here's a breakdown of what you need to consider:

Energy Consumption of Your AC

First, determine the energy consumption of your AC. For instance, if you have a 3,000W AC unit and you run it for 8 hours a day, it would require 24kWh of energy daily.

Total Daily Energy Consumption

However, remember that the AC doesn't run continuously at its maximum power. If, on average, your AC cycles on for 15 minutes every hour during those 8 hours, your actual energy consumption would be closer to 6kWh.

Battery Capacity

For a day's worth of AC use, you'd need a battery system that can store at least 6kWh. But, to ensure you have power during cloudy days or unexpected high usage, it's wise to have a buffer. A battery system with a capacity of 9-12kWh would be more appropriate in this scenario.

Battery Type and Efficiency

Different battery types have varying efficiencies and discharge rates:

• LiFePO4: These are efficient and have a deep discharge capability. If you're using a lithium battery, the 9-12kWh capacity mentioned earlier would be almost entirely usable.
• Lead-Acid: These are less efficient and shouldn't be discharged more than 50% to ensure a longer lifespan. This means you'd need a larger capacity battery to get the same usable energy.  Lead acid batteries are quickly becoming obsolete and not recommended at this time.

Future Expansion

The beauty of modular systems like the Rebel from RevoPower is the ability to expand. Starting with a 9-12kWh system, you can add more batteries as your needs grow or if you decide to power more appliances.

Solar Input

Your battery storage should match your solar input. If you're generating 6kWh daily from your solar panels, but your AC consumes 9kWh, you'll deplete your batteries faster than you can charge them. Using RevoPower's calculator can help you determine the right balance.

Depth of Discharge and Battery Lifespan

Depth of Discharge (DoD) refers to the amount of battery capacity that has been used. Most batteries have a recommended DoD to ensure they have a long lifespan. For instance, if a 10kWh battery has a DoD of 90%, only 9kWh should be used before recharging.

Ballpark Estimates

For a medium-sized home with a 3,000W AC unit running intermittently throughout the day, a battery storage system of around 9-12kWh would be a good starting point. However, this can vary based on factors like insulation, outside temperature, and the efficiency of the AC unit.

5. Inverter Capacity and Soft Start

The inverter should be able to handle the surge wattage of the AC unit. A soft start system can be a game-changer. It reduces the initial surge by gradually increasing the power when the AC starts, making it more compatible with off-grid systems and reducing the strain on your solar setup.

6. Efficiency and Insulation

Ensure your home is well-insulated to reduce the workload on the AC, further decreasing energy consumption.

7. Maintenance and Monitoring

Regularly monitor and maintain both the solar setup and the AC unit for efficient operation.

Conclusion

Transitioning to off-grid solar power for your central AC requires careful planning and consideration. By understanding your home's specific needs and leveraging efficient solutions like the Rebel Solar Generator from RevoPower, you can enjoy a cool home powered by the sun.