Owen Bradley Shopping for keyless entry splits almost immediately into two very different products that share a name. One is a retrofit smart lock, a compact motor that clamps over the thumbturn you already have and turns it for you. The other is a full smart deadbolt, a complete replacement that pulls the old lock out of the door entirely and installs new hardware on both sides. They cost similar money, sit on the same store shelf, and solve the same everyday problem, but they suit completely different doors, tenancy situations, and tolerance for tools. Picking the wrong one usually means a return shipment or, worse, a door that no longer closes properly. This guide breaks the decision down by fit, security rating, install effort, and long-term cost so you can tell within a few minutes which side you fall on.
What Each Type Actually Is
A retrofit smart lock is a one-sided device. It mounts on the interior face of the door over the existing deadbolt’s thumbturn, grips that lever with an adapter, and drives it with a small geared motor. The exterior of the door is untouched. Your existing cylinder, existing key, and existing keyway all keep working exactly as before, and nothing about the door’s appearance from the street changes.
A full smart deadbolt replaces every part of the lock. The old cylinder, bolt, interior thumbturn, and often the strike plate come out and new hardware goes in. The exterior side gains a keypad, a fingerprint reader, or a plain escutcheon, and the interior side houses the motor and batteries. Old keys stop working entirely unless the new lock includes a keyway you rekey to the original.
Everything else about the comparison flows from that one structural difference. One preserves the existing mechanism; the other supersedes it.
The Shared Ground
Both types offer app control, auto-lock timers, access schedules, and entry logs. Both run on batteries. Both integrate with the major smart home platforms depending on model. Feature parity is close enough now that features alone rarely decide the purchase. Fit, permission, and physical security do.
Door Fit: The First Gate
Full deadbolts assume standard North American residential dimensions: a 2-1/8 inch face bore, a 1 inch edge bore, and a backset of either 2-3/8 or 2-3/4 inches. If your door matches those numbers, a replacement drops straight in with no drilling. If it does not, and this is common with older doors, metal storefront-style doors, narrow-stile aluminum doors, and most doors outside that dimensional standard, you are looking at drilling, a mortise-specific product, or no fit at all.
Retrofit locks skip that entire question because they never touch the bore. Instead they care about the shape of the interior thumbturn and the flat space around it. Measure the base plate diameter, the length of the turn lever, and the clearance to the door edge and any nearby handle. Manufacturers publish compatibility lists and printable templates precisely because thumbturn shapes vary so much.
Doors Where Retrofit Wins Automatically
Rentals, condos with hallway appearance rules, doors with an unusual bore, and any situation where a landlord or HOA controls the exterior hardware all point toward retrofit. So does a door with a beautiful antique cylinder you have no interest in discarding. If the existing bolt is mechanically sound and the key situation works, there is no strong reason to rip it out.
Security Ratings and Physical Strength
Security ratings come from ANSI/BHMA, which grades deadbolts on cycle life, bolt strength, and resistance to impact and torque. Grade 1 is the strongest residential and light commercial tier, Grade 2 is the common good-quality residential tier, and Grade 3 is entry-level. A full smart deadbolt carries its own published grade, which means you can shop security directly.
A retrofit lock has no grade of its own because it is not a lock. It inherits whatever grade your existing deadbolt carries. That is a genuine advantage if your door already has strong hardware and a real limitation if it does not. Adding a motor to a flimsy Grade 3 bolt with a half-inch throw and three-quarter-inch strike screws gives you convenience with no security improvement whatsoever.
If your current bolt is the weak link, replacement is the honest answer. Our roundup of the best deadbolt locks is a useful baseline for what strong mechanical hardware looks like, and the best smart deadbolts guide covers models that pair that strength with electronics.
Bolt Throw and Strike Reinforcement
Two mechanical details matter more than the grade label. A bolt should throw a full inch into the frame, not half an inch, and the strike plate should be secured with three-inch screws that reach the wall stud rather than the thin door jamb. Both are cheap fixes and both do more for real-world resistance to kick-ins than any electronics. Whichever lock type you choose, check these first.
Installation Effort Compared
Retrofit installation is genuinely simple. Remove the two long screws holding the interior thumbturn plate, position the retrofit base, reinstall the screws through it, snap the adapter over the turn lever, and clip the body on. Fifteen minutes with a single Phillips screwdriver is typical, and there is no measuring, no drilling, and no alignment fussing. Removal is faster still.
Full replacement is a moderate DIY job. You remove the interior plate, pull the exterior cylinder, slide the bolt out of the edge bore, then reverse the process with new parts. It takes thirty to forty-five minutes on a cooperative door and requires a screwdriver, a tape measure, and patience for alignment. On a door where the old bolt has been binding, replacement is also an opportunity to fix the underlying misalignment, since a fresh bolt and strike plate rarely land in exactly the same spot.
The Alignment Trap
This is the single most common cause of smart lock failure regardless of type. If you can only lock the door by pulling it toward you or shoving your shoulder against it, the bolt is fighting the strike. A human hand can overcome that friction; a small motor cannot. It will jam, drain batteries, and eventually strip. Before installing anything, throw the bolt with the door open and then with it closed. If the closed action is noticeably harder, adjust the strike plate or the hinges first.
Appearance and Everyday Use
Full deadbolts look purpose-built. The exterior gains a proper illuminated keypad, the interior thumbturn is slim, and finishes match common door hardware. Retrofit units are the opposite compromise: invisible outside, bulky inside. A retrofit body typically projects two to three inches from the door face, which is fine on most doors but can interfere with a storm door, a coat hook, or a narrow entryway.
Daily use also differs. A full deadbolt with an exterior keypad lets anyone enter with a code, no phone required. A retrofit lock with no exterior component relies on your phone, a paired keypad accessory, or the original key. If you frequently need to let in family, cleaners, or dog walkers who will not install an app, that difference matters a great deal.
Battery Life and Running Cost
Retrofit motors work harder because they turn an existing thumbturn through an adapter with some mechanical slop, and they are usually smaller. Expect roughly three to six months on four AA cells with regular use. Full deadbolts drive the bolt directly with a purpose-designed motor and commonly run six months to a year on the same cells. Always-on WiFi cuts either figure substantially compared with Bluetooth or a low-power hub protocol.
Purchase prices overlap heavily. Both categories run from budget models around fifty dollars to premium units past three hundred. The real cost difference is that a full replacement may also mean buying a matching handle set to keep finishes consistent, while a retrofit spends nothing on the exterior. Compare the best digital deadbolts across price tiers before assuming replacement is the expensive route.
Choosing in Five Questions
- Do you own the door? If not, retrofit unless you have written permission.
- Is the existing deadbolt strong and smooth? If yes, retrofit preserves it. If it binds or is Grade 3, replace.
- Does the door use a standard bore and backset? If no, retrofit or a specialty product.
- Do people without your phone need to get in? If yes, you want an exterior keypad, which favors replacement.
- Do you care how the interior looks? Retrofit bodies are visibly bulky. Replacement is cleaner.
Answer these honestly and the decision usually makes itself in under a minute.
Mistakes Buyers Make
The first is assuming retrofit means less secure. Mechanically it is identical to whatever bolt is in the door, which can be excellent. The second is the mirror error: assuming a full smart deadbolt is automatically stronger. A cheap electronic deadbolt with a Grade 3 rating is weaker than a good mechanical Grade 1 bolt with a retrofit motor on it. The third is buying before measuring, either the thumbturn or the bore, which drives most returns in this category.
A fourth mistake is discarding the original hardware. Keep it bagged and labeled, whether for a rental move-out or simply as a fallback if the electronics disappoint. Finally, many buyers never read the broader comparison between electronic and mechanical security; the smart deadbolts versus traditional locks breakdown covers the trade-offs that marketing copy usually skips.
Frequently Asked Questions
Can I still use my old key with a retrofit lock?
Yes, always. The cylinder is untouched, so every existing key keeps working, which is why retrofit is the default recommendation for renters and shared properties.
Does a retrofit lock work on a smart lever handle?
Generally no. Retrofit devices are designed for deadbolt thumbturns, not lever latches. If your door has only a keyed lever and no deadbolt, replacement is the practical route.
Which one handles a misaligned door better?
Neither handles it well, but replacement at least lets you reposition the strike plate during installation. Fix alignment before buying either type.
Do full smart deadbolts need drilling?
Not on a standard door with an existing deadbolt. Drilling is only required if the door has no deadbolt bore at all or uses non-standard dimensions.
Which lasts longer?
Full deadbolts generally, because the motor is matched to the bolt and there is no adapter slop. Retrofit units also depend on the health of an older bolt they did not replace. Comparing options across the best deadbolt smart locks shows how cycle-life ratings differ between tiers.
Final Thoughts
Retrofit and full smart deadbolts are not competing for the same buyer so much as sorting buyers by circumstance. If you cannot or do not want to change the exterior of your door, if your existing deadbolt is solid, or if other people hold keys you must not invalidate, retrofit is clearly correct and installs in a quarter of an hour. If you own the door, want an exterior keypad, need a stronger bolt than you currently have, or simply want the cleaner look, replacement is worth the extra half hour.
Measure before you buy, check that the bolt throws freely with the door closed, and reinforce the strike plate with long screws regardless of which path you take. Get those fundamentals right and either type will serve reliably for years, well past 2026.
