Smart Lock vs Rekey Cost Calculator

How This Smart Lock vs Rekey Cost Calculator Works

This calculator compares the total cost of installing and owning a smart lock with the ongoing cost of rekeying a traditional lock over time. It is designed for homeowners, landlords, property managers, and small business owners who regularly need to change who has access to a door. By entering a few key numbers, you can estimate whether paying more up front for a smart lock is likely to be cheaper or more expensive than paying a locksmith to rekey your existing lock as people come and go.

The tool focuses purely on direct, predictable cash costs: the price of the smart lock itself, the cost of replacement batteries, and the cost and frequency of traditional rekey visits. It does not attempt to measure convenience, security differences, or the value of features such as activity logs or remote access. Instead, it gives you a simple financial baseline: over your chosen analysis period, which option is likely to cost less money out of pocket?

To use the calculator, you enter:

• Smart lock purchase cost ($) – how much you expect to pay for the smart lock hardware for a single door.
• Battery replacement cost per year ($) – your estimated annual spending on batteries (or charging) to keep the smart lock powered.
• Smart lock lifespan (years) – how long the smart lock is expected to remain usable before it needs replacement.
• Rekey cost per visit ($) – what a locksmith typically charges to rekey that door once.
• Expected rekeys per year – how many times per year, on average, you expect to need the lock rekeyed.
• Analysis period (years) – how many years into the future you want to compare total costs.

After you click the calculate button, the tool computes the total smart lock cost and the total traditional rekey cost over the analysis period, then highlights which option is cheaper and by how much.

Cost Formulas Used in the Calculator

The calculator applies simple arithmetic to estimate total costs. For clarity, the symbols below describe the key inputs and outputs:

• P = smart lock purchase price (dollars)
• B = battery replacement cost per year (dollars per year)
• L = smart lock lifespan (years)
• K = rekey cost per visit (dollars per rekey)
• N = expected rekeys per year (rekeys per year)
• Y = analysis period (years)

The calculator effectively uses the analysis period in conjunction with the smart lock lifespan. If your analysis period is longer than the smart lock lifespan, the real-world cost would include at least one replacement lock. Many users simply set the analysis period less than or equal to the lifespan so that only one purchase is counted. Conceptually, the basic cost formulas are:

Smart lock total cost over the analysis period

When you analyze a number of years that does not exceed the lock’s useful life, the model is:

Cs = P + (B × Y)

where C_s is the total smart lock cost over the analysis period. This reflects a single up‑front purchase plus recurring battery costs.

Traditional rekey total cost over the analysis period

For a conventional lock that is rekeyed as needed, the model is:

Cr = K × N × Y

where C_r is the total rekeying cost over the analysis period.

Expressed using accessible mathematical markup, the traditional rekey formula can be written as:

This means the total rekey cost equals the cost of one rekey, multiplied by how many rekeys occur per year, multiplied by how many years you are evaluating.

Break-even rekey frequency

The break-even point is the rekey frequency at which the cost of owning the smart lock equals the cost of rekeying over the analysis period. Setting the two totals equal, and solving for N (rekeys per year), gives:

P + (B × Y) = K × N × Y

Rearranging for N:

N = [P + (B × Y)] / (K × Y)

This provides a simple sanity check when reading the results: if you expect to rekey more often than this break-even frequency, the smart lock is likely to be the cheaper option over the chosen period; if you rekey less often, traditional rekeying will usually cost less.

Interpreting Your Results

After you enter your numbers and run the calculation, you will typically see three key pieces of information:

• Total smart lock cost over the analysis period, including purchase and batteries.
• Total traditional rekey cost over the same period, based on your expected rekey frequency.
• Which option is cheaper, and by approximately how much.

If the smart lock total is lower, it suggests that the up‑front purchase is likely to pay for itself within the analysis period under your assumptions about rekey frequency and costs. If the rekey total is lower, it suggests you may not change keys often enough to justify the additional smart lock expense purely on cost grounds.

Because both smart lock and rekey costs scale with time, it can be useful to experiment with different analysis periods. For example, a smart lock might be more expensive over just two years, but become cheaper if you extend the analysis to five or seven years. Likewise, your estimate of expected rekeys per year is a major driver of the result. If you are unsure, try a low, medium, and high scenario to see how sensitive the outcome is to that assumption.

You can also interpret the numbers on a per‑year basis. Divide each total by the analysis period to estimate an average annual cost of access control for the door. This can be helpful when you are budgeting across multiple doors or comparing options with different lifespans.

Worked Example: Landlord With Seasonal Tenants

Consider a landlord who rents out a small house on a seasonal basis, with a new tenant each season. For simplicity, assume there is one primary door to manage.

Suppose the landlord uses these figures:

• Smart lock purchase cost, P = $200
• Battery replacement cost per year, B = $10
• Smart lock lifespan, L = 5 years
• Rekey cost per visit, K = $80
• Expected rekeys per year, N = 4 (one at the start of each season)
• Analysis period, Y = 5 years

Step 1: Smart lock total cost

Over five years, the smart lock cost is:

Cs = P + (B × Y) = 200 + (10 × 5) = 200 + 50 = $250

This assumes the lock lasts the entire five years without needing replacement and that battery costs remain roughly constant.

Step 2: Rekey total cost

Over the same five‑year period, the rekey cost is:

Cr = K × N × Y = 80 × 4 × 5

First calculate the yearly rekey cost:

80 × 4 = $320 per year.

Then multiply by five years:

320 × 5 = $1,600

So the landlord would spend about $1,600 on rekeying over five years, versus $250 on the smart lock option under these assumptions.

Step 3: Break-even check

Using the break-even formula for N:

N = [P + (B × Y)] / (K × Y)

Plug in the numbers:

N = [200 + (10 × 5)] / (80 × 5) = 250 / 400 = 0.625

This means that if the landlord expects more than about 0.63 rekeys per year (a little more than once every two years), the smart lock becomes the cheaper option over a five‑year period. Since the landlord in this example expects four rekeys per year, the smart lock clearly wins on cost over five years.

Comparison of Typical Scenarios

The table below gives simplified, illustrative numbers for three different situations. These are only examples to help you think about your own use case. You should plug your own costs into the calculator for a more precise comparison.

These examples highlight the main pattern: as the number of expected rekeys per year increases, the economic case for a smart lock strengthens. When rekeys are rare, the traditional approach usually remains cheaper, at least in purely financial terms.

Assumptions and Limitations

This calculator simplifies reality in order to stay easy to use. When interpreting the results, keep the following assumptions and limitations in mind:

• Installation costs are excluded. The model assumes that installation costs for both smart locks and traditional locks are either similar or negligible. In practice, professional installation can add meaningful expense, especially for complex smart locks.
• Accessories and connectivity are not included. Any optional Wi‑Fi bridges, hubs, door sensors, or subscription services associated with a smart lock are not counted. If your chosen lock requires recurring subscription fees, those should be added manually to your battery cost per year to approximate the total ongoing cost.
• Single‑door focus. All inputs and results are for one door. If you manage multiple doors, you can scale costs by the number of doors, assuming similar usage patterns, or run separate calculations for each door type.
• Constant prices over time. The calculator assumes that rekey costs, battery prices, and smart lock prices remain constant over the analysis period. It does not adjust for inflation, discounts, or future price changes.
• Constant rekey frequency. The expected rekeys per year value is treated as an average that stays the same every year. Real‑world patterns may be lumpier (for example, more rekeys in the first year, then fewer later).
• Smart lock lifespan is user‑supplied. The lifespan input is not automatically enforced in the cost formula beyond your own judgment. For a fair comparison, choose an analysis period that does not significantly exceed the lock’s realistic lifespan, or manually account for the cost of a replacement lock if you go longer.
• Security and risk differences are ignored. The model does not attempt to price in differences in security level, the risk of lost keys, the chance of a digital lockout, or potential liability. It strictly looks at direct monetary costs.
• Repairs and failures are omitted. Occasional repair costs, early product failures, or warranty replacements are not modeled. In practice, these can affect total ownership cost for both smart locks and traditional locks.
• Tax, accounting, and financing effects are not modeled. The calculator does not consider how you pay for the lock (cash vs. financed), nor does it include tax deductions, depreciation, or business expense treatment.
• User behavior and convenience are unpriced. Benefits like not having to schedule locksmith visits, being able to revoke access instantly, or offering keyless entry to guests may be valuable to you but are not converted into dollar terms here.

Because of these simplifications, you should treat the output as an order‑of‑magnitude comparison rather than a precise financial forecast. It is most useful for understanding which cost drivers matter most in your situation and for exploring “what‑if” questions such as “what if my rekey cost doubles?” or “what if I start hosting short‑term guests?”

Using the Calculator for Better Decisions

To get the most value from this tool, consider running several scenarios with different assumptions. Start with your best estimate for each input, then adjust one input at a time to see how sensitive the results are. For example:

• Increase or decrease the expected rekeys per year to reflect unusually busy or quiet years.
• Try a higher analysis period if you tend to keep hardware for a long time.
• Test different smart lock prices to compare basic models to feature‑rich options.
• Add any extra yearly subscription or connectivity fees to your battery cost per year to approximate all recurring smart lock costs.

Combined with your own judgment about convenience and security, the calculator’s cost comparison can help you decide whether switching to a smart lock is primarily a matter of comfort and features, or whether it also makes clear financial sense over the period you care about.