ADU Impact Fees: Phoenix vs Tempe

How much are ADU impact fees in Phoenix?

Total impact fees typically run $4,000-$8,000 for a residential ADU. Under HB 2928, Phoenix must charge ADUs at no more than 50 percent of single-family rates in each category (water, wastewater, parks, fire, police, library, streets).

Are Phoenix ADUs under 750 sq ft exempt from impact fees?

No automatic exemption like California. Arizona HB 2928 caps ADU fees at 50 percent of single-family rates but does not provide a size-based exemption. Phoenix charges proportional fees regardless of ADU size.

How much are impact fees for a Tempe ADU?

Tempe does not charge a dedicated ADU impact fee. You pay standard building, plumbing, mechanical, and electrical permit fees based on construction valuation, plus water and sewer development fees only if a new meter or service is installed. Request a written fee estimate from Tempe Community Development before submittal.

Can Tempe charge me the full single-family impact fee for an ADU?

No. Under ARS 9-461.18 (HB 2720), fees that would effectively prohibit ADU construction are barred. Tempe applies its standard transportation, parks, and public safety impact fees to new principal-unit construction, not as a duplicate charge on accessory dwelling units sharing the existing lot.