How this radon payback planner works
The calculator compares your baseline radon concentration to a target (residual) radon concentration after mitigation. The difference between those two values drives the estimated benefits. Costs come from the installation price and the electricity needed to run a mitigation fan continuously.
The output is a net present benefit over your chosen analysis horizon. A positive number means the model’s estimated benefits exceed the model’s estimated costs (in today’s dollars). A negative number means the opposite. This is not medical advice and not a substitute for professional testing or local code requirements; it is a planning tool.
Inputs (what to enter and how to choose values)
- Baseline radon concentration (pCi/L): Use a long-term test result when possible (often 90+ days) because radon varies by season. If you only have a short-term test, consider running a conservative scenario with a slightly higher baseline.
- Target radon concentration after mitigation (pCi/L): This is the level you expect after mitigation. Many homeowners aim for well below 4 pCi/L; your contractor may provide an expected range.
- Mitigation system installation cost ($): Include permits and any electrical work if those are part of your quote.
- Continuous fan power draw (watts): Typical systems run 24/7. Use the fan label rating or contractor estimate.
- Electricity rate ($/kWh): Use your all-in rate (supply + delivery). If your bill varies by season, use an annual average.
- Current home value ($): A reasonable estimate is fine (recent appraisal, comparable sales, or a conservative market estimate).
- Value of statistical life proxy ($): This is a policy-style monetization input used to compare risk reductions. If you prefer not to monetize health risk, you can set this lower to see how much the result depends on it.
- Analysis horizon (years): Use how long you expect to own the home or how long you want to evaluate costs and benefits.
Model details (formulas and assumptions used)
The calculator uses three main components: fan energy cost, estimated home-value gain, and a simplified health benefit. It then discounts future energy costs at a fixed 3% annual discount rate.
1) Fan electricity cost
Annual fan cost is computed from watts to kWh per year:
kWh/year = (watts ÷ 1000) × 24 × 365
Annual fan cost ($/year) = kWh/year × electricity rate
2) Present value of energy over the horizon
The tool discounts each year’s fan cost using 3%:
PV(energy) = Σ (annual fan cost ÷ (1 + 0.03)year) for year = 1…N
3) Estimated home-value gain from radon reduction
The model estimates a value gain proportional to the fraction of radon reduced, capped at 3% of home value:
reduction = max(baseline − residual, 0)
reductionShare = reduction ÷ baseline
valueGain = min(homeValue × 0.03, homeValue × reductionShare)
This is intentionally conservative and simplified. Real market impacts vary by region, disclosure rules, and buyer expectations.
4) Monetized health benefit (simplified)
The calculator uses a linear coefficient to translate radon reduction into a risk reduction proxy and then multiplies by your VSL input:
healthBenefit = VSL × reduction × 0.0012
The coefficient is a rough planning approximation and does not account for smoking status, age, or local epidemiology.
5) Net present benefit
Finally:
netBenefit = valueGain + healthBenefit − mitigationCost − PV(energy)
Worked example (using realistic inputs)
Example scenario: baseline radon is 7.5 pCi/L, target is 2.0 pCi/L, installation cost is $1,500, fan draw is 90 W, electricity is $0.15/kWh, home value is $350,000, VSL proxy is $9,000,000, and the horizon is 10 years.
- Radon reduction: 7.5 − 2.0 = 5.5 pCi/L
- Fan kWh/year: (90/1000) × 24 × 365 ≈ 788 kWh/year
- Fan cost/year: 788 × 0.15 ≈ $118/year
- PV of energy (10 years @ 3%): roughly $1,000 (discounted sum)
- Value gain (capped): reductionShare = 5.5/7.5 ≈ 0.733 → homeValue × share ≈ $256,550, but cap is 3% → $10,500
- Health benefit: 9,000,000 × 5.5 × 0.0012 = $59,400
- Net present benefit: 10,500 + 59,400 − 1,500 − 1,000 ≈ $67,400
The example illustrates how sensitive the result can be to the health monetization input and the value-gain cap. If you want a “pure cash” view, reduce the VSL proxy and see how the net benefit changes.
Scenario table (what it shows)
After you submit the form, the table shows three outcomes:
- Target outcome: uses your target residual radon.
- Conservative performance: assumes residual radon ends up 25% higher than target (less reduction) and slightly lower fan watts.
- Optimized performance: assumes residual radon ends up 25% lower than target (more reduction) with slightly higher fan watts and a small extra cost.
Limitations and assumptions
- Not a medical risk model: The health benefit is a simplified linear approximation and may not reflect your household’s risk profile.
- Market value is uncertain: The value-gain estimate is a heuristic with a 3% cap; local disclosure rules and buyer behavior can dominate.
- Continuous operation assumed: Fan energy assumes 24/7 operation year-round.
- Maintenance excluded: Retesting, fan replacement, and monitoring costs are not included.
- Discount rate fixed: The model uses 3% for energy PV; if your personal discount rate differs, treat results as directional.
Related home planning tools
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