Principle of Substitution in Real Estate Appraisal Explained
The principle of substitution in real estate appraisal: definition, how it shapes all three approaches to value, comp adjustment math and practice questions.
By PSI Exams Prep Editorial Team 5 min read
What is the principle of substitution?
The principle of substitution says that a buyer won't pay more for a property than it would cost to acquire an equally desirable substitute, either a similar property on the market or the cost of building one, assuming there's no costly delay. It's the reason similar homes in the same area sell for similar prices, and it's the foundation of real estate appraisal.
If two nearly identical houses sit on the same street, one listed at $400,000 and the other at $375,000, an informed buyer chooses the cheaper one. The lower price caps what the market will pay for both.
How does it drive the three appraisal approaches?
| Approach | How substitution applies | Best for |
|---|---|---|
| Sales comparison | Value is indicated by recent sales of similar substitute properties, adjusted for differences | Homes and land with active markets |
| Cost | A buyer won't pay more than the cost to build an equally useful substitute (land value plus construction cost, minus depreciation) | New or special-purpose buildings |
| Income | An investor won't pay more than the price of a substitute investment producing similar income at similar risk | Rental and commercial property |
How do you adjust comparable sales?
In the sales comparison approach, the appraiser picks recent sales of similar properties (comparables, or “comps”) and adjusts each comp's sale price so it reflects what the comp would have sold for if it were just like the subject property. The rule:
- Comp better than the subject: subtract the value of the extra feature (“CBS: comp better, subtract”).
- Comp poorer than the subject: add the value of the missing feature (“CPI: comp poorer, increase”).
In real appraisals, adjusted prices rarely match exactly. The appraiser reconciles them, giving the most weight to the comps that needed the fewest and smallest adjustments, to reach a final opinion of value.
Exam trap
Related appraisal principles
| Principle | In one sentence |
|---|---|
| Contribution | A feature is worth what it adds to market value, not what it cost to install |
| Conformity | Value is maximized when a property is similar to others in the neighborhood |
| Highest and best use | The legally permitted, physically possible, financially feasible use that produces the highest value |
| Anticipation | Value is the present worth of expected future benefits |
| Progression and regression | A modest home gains value among better homes (progression); a superior home loses value among lesser ones (regression) |
| Supply and demand | Value rises when demand outpaces supply, and falls when supply outpaces demand |
Valuation is a major section of the national portion. Pair this with types of listing agreements and appurtenances, then follow the plan in how to pass the PSI real estate exam.
Practice questions
Question 1. A comparable property sold for $350,000. It has a swimming pool worth $20,000; the subject property does not. What is the comparable's adjusted sale price?
- A. $370,000
- B. $350,000
- C. $330,000
- D. $340,000
Show answer
Answer: C. The comparable is better than the subject, so subtract the pool's value from the comparable: $350,000 − $20,000 = $330,000.
Question 2. A buyer refuses to pay $400,000 for a house because a nearly identical house nearby is listed for $375,000. Which appraisal principle does this illustrate?
- A. Contribution
- B. Substitution
- C. Conformity
- D. Anticipation
Show answer
Answer: B. The buyer won't pay more than the cost of an equally desirable substitute, which is the principle of substitution.
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What is the principle of substitution in real estate?
Which appraisal approach is based on the principle of substitution?
Do you adjust the comparable or the subject property?
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