Almost every ADU price you will see quoted online is a unit price. It is the number a manufacturer can state with confidence, because it is the part they control. The number you actually write cheques against is larger, and the difference is not padding — it is the work of turning a piece of ground into a serviced building site.
A total ADU cost has two halves. The first is fixed and knowable today: the home itself. EVO publishes those prices — $145,800 for the 350 sq ft Compact, $157,920 for the 430 sq ft Studio, $179,680 for the 560 sq ft One, $203,050 for the 715 sq ft Two, and $238,000 for the 800 sq ft Two Plus. Each covers the factory build and fire sprinklers, and none of them move based on how the conversation goes.
The second half depends on your parcel, and it is where estimates diverge:
- Site work — about $55,000 to $67,000 by model. One contract covering the foundation, utility connections, delivery and installation. Slope, soil, trench distance and access set where you land; it is priced exactly after a site visit.
- Permit fees and reports, a $10,000 allowance. City fees paid by you at cost, plus the soils report and boundary survey your plan set needs. Units under 750 sq ft are exempt from development impact fees under state law — one reason four of the five EVO models sit below that line.
Added together, that is roughly $65,000 to $77,000 on top of the unit — so a realistic all-in range for a detached ADU in California runs from about $211,000 to about $315,000, depending on which home you choose and what your lot demands.
Why cost per square foot is a misleading way to compare
Dividing a project total by floor area produces a number that looks comparable and is not. A 350 sq ft studio and an 800 sq ft two-bedroom both need one kitchen, one bathroom, one set of utility connections, and one foundation. Those fixed costs spread across fewer square feet in a small unit, so the smaller home almost always shows a higher cost per square foot while costing less in total. Compare total project cost against what the finished home does for you — rent, family space, resale — not against a ratio.
The three things that actually move your number
Access. How the unit reaches its final position is the single largest swing factor in site work. Clear side-yard access is straightforward. A narrow gate, a steep slope, or overhead power lines means more equipment, more time, or a different delivery method.
Distance to services. Every foot between your existing water, sewer, and electrical connections and the new unit is trenching. A unit placed near the main house is cheaper to service than one at the back of a deep lot.
Your jurisdiction. Permit fees, plan-check timelines, and local requirements vary between cities, even neighbouring ones. State law sets a floor on what must be allowed, but the fee schedule is local.
What this estimator can and cannot tell you
The estimator above pulls your parcel from county records, measures the buildable area after setbacks, determines which EVO models physically fit, and applies the fixed unit price plus the published adder ranges. That gives you a defensible total range for your specific address in about a minute, without talking to anyone.
What it cannot do is see your soil, your panel, or your gate. Those set where inside the range you land, and they need a site evaluation. Treat the output as a decision tool — enough to know whether this project is worth pursuing — rather than as a quote.