Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Tempe ADU cost →Building an ADU in Tempe costs between $120,000-$250,000 for new construction, with per-square-foot costs averaging $140-$280. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $60,000-$140,000, while prefab/modular ADUs fall in between at $85,000-$200,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | Building permit and plan review fees based on valuation — Confirm with Tempe Community Development |
| Impact Fees | Confirm with Tempe Community Development; state law bars ADU-specific parking in-lieu fees |
| Site Prep & Foundation | $10,000 – $35,000 |
| Framing & Structure | $15,000 – $45,000 |
| Plumbing | $8,000 – $20,000 |
| Electrical | $5,000 – $15,000 |
| HVAC | $3,000 – $8,000 |
| Interior Finishes | $15,000 – $40,000 |
Quotes for the same ADU commonly vary 20–40% between builders. Get up to 3 free quotes from ADU builders serving Tempe — no obligation.
Get Tempe builder quotes →Permit fees in Tempe are Building permit and plan review fees based on valuation — Confirm with Tempe Community Development. The review timeline is Typically 4-8 weeks for residential plan review — Confirm with Tempe Community Development, with plan check: 2-4 weeks typical — Confirm with Tempe Community Development. Impact fees are Confirm with Tempe Community Development; state law bars ADU-specific parking in-lieu fees. Pre-approved plans: No city pre-approved plan library — Confirm with Tempe Community Development.
| 1-Bedroom Rent | $1,300-$1,700/month |
| 2-Bedroom Rent | $1,600-$2,100/month |
| Annual Rental Income (est.) | $18,000/year |
| Payback Period (est.) | 10.3 years |
| Short-Term Rental | Allowed with an Arizona/Tempe STR license, but the owner must live on site if the ADU was built on/after Dec 20, 2024 |
| Overall ROI Estimate | 7-10% annual return |
A typical ADU in Tempe generates approximately $18,000 per year in rental income based on average 1-bedroom rents. At an average construction cost of $185,000, the estimated payback period is 10.3 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Tempe and varies by market (often less than build cost).
1. Garage conversions save 40-60% vs new construction since the shell already exists. Average cost in Tempe: $60,000-$140,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $85,000-$200,000.
3. Pre-approved plans — Tempe does not offer a pre-approved/standard ADU plan program yet, so budget for custom architectural plans (typically $3,000-$15,000).
4. State grants — California's CalHFA ADU grant (up to $40K) is currently paused; check calhfa.ca.gov/adu for status and your state for active programs.
5. Get multiple bids — ADU contractor pricing varies 20-40% for the same project. We recommend getting at least 3 quotes.
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