I have small single family homes, 2/1s . I’ve decided to do through the wall A/C to prevent theft. Problem has been getting the carpenter to frame that in, but that’s a whole other issue.

Besides the caging, or chain link fencing,which is probably the best bet, you might also try planting thorny bushes all around. The Fairy is a rose bush that handles quite a bit of shade, can be found cheap on any number of garden catalogue websites. The Fairy is low enough that it won’t inhibit air flow that much. But, lots of thorns.

Of course, when the unit needs maintenance, you’ll want to trim the roses way back or the HVAC tech will hate you, curse you and the horse you rode in on. Wear leather gloves when trimming roses.

I purchased some some Metal Fencing Panels and made a cage to go around my exterior compressor unit. I welded most of it together but kept a removable section for maintenance access. I put ringed bolts into the concrete and epoxy'ed them into place then used pad locks to attach the cage to the ground bolts. This couldn't be lifted away but can be removed with a key if necessary.

Of course, there is greater risk at a vacant place.

While my rooming house was under contract to purchase, mine (well - the bank's) were stolen / destroyed by someone who cut the chainlink and rolled it out out of the way.

My HVAC guy says he's never seen any messed with that were behind privacy fence panels. Out of sight, out of mind.

Several ways to stop. #1. Have courts / law make it a felony too steal or purchase one from anyone without a license to sell. #2 Hope that your chief of police and local judge have theirs stolen. #3 S&W 38.

In some bad neighborhoods, I've seen welded steel cages completely enclosing them, however the gate and lock are still the weak spots and in spite of the thick gauge steel bar welded cage, the units were stolen. No matter how strong the cage is, the weak point is always the gate and the padlock. So, I don't think fencing or caging works as a solution.

However, I had a new condenser in a high-crime area and everyone knew the house was vacant while we were remodeling. Here's what I did. I placed video surveillance signs around the house and next to the condensers. I placed a camera in the window facing the condensers. I also installed motion lights in that area to light up any visitor.

The best thing I did was to place an alarm system in the home that could be monitored. Instead of wiring the fire alarm sensor, I used that "always armed" fire zone to serve as protection for the condenser. That means that the condenser was protected whether the system was armed or disarmed. However, any time you needed to work on the condenser unit, you had to call the alarm monitoring company and place the unit on test mode so they would ignore the alerts.

Around the case, where there was a removable panel, I had the alarm company place contact sensors so there was no way to remove the top or sides without the alarm sounding.

By the way, when the alarm was installed, I placed two sirens in the attic vents facing outside so the neighborhood would take notice.

The second thing we secured was the copper and electrical cables running to the condenser. The alarm company ran a loop wire down the tubing of all cables and pipes running to the condenser. If any pipe or cable was cut, that loop would get cut and the alarm would sound.

The third thing we did is put sensors under the unit so that if the unit was lifted, the alarm would sound.

The fourth thing we did was place alarm stickers on the unit near the contact sensors so anyone looking at the unit knew this one would be difficult to steal.

So basically the alarm prevented anyone from removing covers or cutting cables/pipes, and a camera looked over all of it.

In short, the best way to protect the unit is by making it harder to not be noticed trying to take it. That's the best method. Since most condensers are hidden in the back, most locks and cages don't discourage thieves since they know they have lots of time to work on it without fear of getting caught. Make sure your solution attacks their fear of getting caught and you should be good to go.

MYOB:

None that are fool-proof, but...

1) Cage around it

2) Put a security system sign and/or fake cameras on the eaves near that part of the house

3) Add a motion light/alarm sensor in the area

I only mount on roofs now, takes time and costs more but not much happens up there, they get privacy fencing painted white matching the metal roofing.

LLOTF,

There are already laws in place to prevent illegal sale of copper coils. Any nonferrous metals require a permit for sale. Any AC coils also require a business license or a receipt for a new unit to sale. And the buyer MUST file a copy of a picture ID and pay with a check, not cash.

Unfortunately, the criminals find a way around these laws.

Typically your unit only needs to be visibly harder to steal than the next guy's. Thieves are lazy.

A quick way to secure an AC is to drive an 8 foot T post deep into the ground on each side of the unit. Attach 2 lengths of chain to the T posts using nuts, bolts, and washers. The chains should cross over the unit. Peen the bolts over to prevent removal .