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There are two things you quickly learn about running an air condition unit on solar power. It requires a lot of solar panels and two, batteries are important. But is it possible to run a 1.5 AC on solar power without using batteries? In certain situations yes, but in others, a big no.
It takes a 3kw to 10kw solar array to run a 1.5 ton AC. An off the grid solar system needs at least a 600ah battery bank to power the AC when there is no sun, but a grid tied system doesn’t require batteries because it can draw from the power company.
To better understand this, let us look at the two situations and how they differ.
When a 1.5 Ton AC Does Not Need Batteries
Solar systems for homes today are either on the grid or off the grid. The grid refers to the power company which supplies electricity.
If your home is on the grid, it means you have access to electrical power from the utility company. You can use solar or electrical power. For example you can run a refrigerator, microwave or your 1.5 ton AC on the grid, freeing up your solar panel for well pumps, heat lamps and other appliances.
A grid tied solar system does not need batteries to run a 1.5 ton AC. If you have a 3kw to 10kw solar panel, there won’t be any problems running any appliance. But in case solar power output drops – sun goes down, there is damage, etc. – you can tap the grid and operate the system on electricity.
You have two ways to use an AC or any appliance, via solar or electric power. And no worries about wasted solar power as the excess energy goes straight into the power grid.
Being on the grid definitely has benefits and makes running an AC and other power hungry appliances easier. This is why it is the most commonly used solar system setup today.
The problem with being on the grid is if the lights goes out, you have no access to solar power. The system is automatically shut down for the protection of personnel who have to repair the power lines.
So if there is a long blackout you have no way to run any appliance. Unless you are off the grid or have a large battery bank.
When a 1.5 Ton AC Needs Batteries
An off the grid solar system is completely independent. All the power comes from your solar panels, batteries and whatever other power source you have, such as a generator.
A battery bank is a must in an off the grid cabin, house or RV. Solar panels can only provide power during the day, and any unused power goes to waste without storage.
A battery bank serves as a storage for this excess solar power. It will also power your air conditioner when the solar array cannot.
An off the grid system means you are no longer dependent on the power company. Your neighborhood can suffer a blackout and you won’t be affected. With sufficient power from the solar system and batteries, you can use an AC and other appliances day and night.
The drawback are the batteries. You will need a lot of them especially for large devices. Fortunately there are compact, energy efficient appliances you can turn to for cost savings.
How Many Batteries to Run a 1.5 Ton AC?
There are many types of air conditioners, and even if you narrow it down to 1.5 tons, there are variations due to different designs and features. However the following is a general guideline that may be used.
The easiest way to check the power consumption of a 1.5 AC is to look at the label. To manually compute, multiply the wattage by the number of operating hours.
A 1.5 ton AC consumes 1500W to 2000W per hour. However its surge watts can be 2 to 3 times higher, so for a 1500W AC, the total wattage is around 3000W to 5000W, Your solar system must be able to supply that power.
The following example is for the AC only. It assumes the battery will not be used for other solar appliances and that you have an inverter in place. If you are going to use other appliances, increase the solar system size.
Sample Calculation of AC Battery Use
Suppose you have an air conditioner and want to run it for 5 hours a day. If the air conditioner consumes 1500 watts an hour, that is 7200 watts a day (1500 x 5 = 7200).
So we need a battery with a 7200 watt capacity. A 300ah battery is 3600 watts. Theoretically it can run the AC, even with its 3000 surge watts. However lead acid batteries have a 50% usability capacity, so only 1800 watts is available.
The ideal scenario is to have a couple of 300ah lithium batteries like the Lossigy Deep Cycle LiFePO4 12V. With these you can run the AC unit without difficulty.
1800 watts is enough for the running watts but insufficient for the surge watts. If you double that to 600ah however it is enough. Even with a 50% DOD, that is still 3000 watts available.
This calculation assumes you are using a 12V lead acid battery as they are the most popular. 24V and 48V batteries have more watts compared to a 12V of the same size, though they cost more.
Also keep in mind that you should only use energy efficient appliances with solar systems. Older air conditioning units consume more than 3000 watts, and the surge could be 5000 watts or more. If you run other appliances on your solar system, energy efficient appliances are a must.
Lithium batteries are still expensive but do allow you to use more power per charge. In many cases, a lead acid battery bank is enough for an AC. The appliance already consumes a lot of power and using a lithium battery bank is an additional expense. But if you want the best batteries for solar appliances, lithium is the right option.
How Many Solar Panels to Run a 1.5 Ton AC?
Like the batteries it depends on the AC power consumption. Using our example of a 1500W AC with a 3000W surge watt demand, a 3kw solar system is the minimum with 4kw to 5kw being ideal.
It takes 15 x 350W solar panels to produce 5000 watts / 5kw an hour. With this you can comfortably operate the AC and still have a couple of thousand watts for other appliances. Since the sure watts is only a second, it frees up a lot of power for use elsewhere.
You can also use 200 watt solar panels like the Newpowa Monocrystalline 12V though you will need more compared to a 300 watt PV module.
You can operate a 1.5 ton AC with these solar array as long as there is power output from the panel. If you are going to use the AC for 5 hours a day, say from 11:00 AM until 4:00 PM, the solar array can handle it.
But you need a powerful battery bank and inverter if you want to use the system at night. For a 3000 watt unit, you need a 4000 to 5000W inverter. For the batteries, 600ah will be enough as we mentioned..
Factors That Affect AC Power Consumption
The stated power consumption of an AC is based on general usage only. In the real world, there are many factors that could increase or decrease the amount of power being used.
More People Means More Power Required. The human body produces heat, and the more people in a room, the harder an AC has to work to cool the air. This increases watt usage, very important if the power supply is at its limit. This is why we recommend having reserve power in case there is a need for it.
More Solar Power is Better. If your AC unit needs 3000 watts, install a 3500W system. You can even go for 4000W or 5000W, but never settle for 3000W. It is never a good idea to run solar systems at their limit, nor inverters and charge controllers. When your solar array or battery bank is always at the limit, overloading can occur. The solar panel may overcharge the battery or the inverter could just give out. This is especially true with air conditioning units.
Temperature Matters. The lower the temperature, the faster an AC can cool a room. The hotter it is, the more power is required. Granted there is not much we can do about this since the only time we use an AC is during the summer.
Area to Cooled Down/ The larger the room or area an AC needs to cool, the greater the power requirement is going to be. If you combine this with several people in the room, expect the wattage to be higher than the amount given in the label.
Design. Some air conditioning units are just more energy efficient than others. It is similar to any other appliance or gadget where one product is superior to another even though the specs are very similar. So it pays to buy from a reputable manufacturer.
Solar panels and batteries today have become powerful enough to handle majority of appliances. However air conditioning systems still require a lot of power. As shown here, the need – or lack of need – for batteries depends mostly on your setup.