A prefab ADU advertised at $150,000 in California does not cost $150,000. We checked 14 companies selling prefabricated accessory dwelling units to California homeowners on 31 August 2026, reading their pricing pages, model pages and FAQs. Eleven publish a price. Eight say what that price covers. Three sell a finished project rather than a unit. One publishes a written list of what sits outside the number.
Renology does not work with, and is not paid by, any company on this list. We earn a fee only when a homeowner we match with a contractor from our own network hires them, and none of those contractors appears here. Nothing on this page can be bought.
- Published figures in this set run from $15,000 to $781,246, and they are not measuring the same thing.
- Site work is the gap. Foundation, trenching, utility connections, crane access and permit fees sit outside most published prices.
- Only Abodu publishes a written list of what is quoted separately, including trenching beyond 50 feet and craning beyond 100 feet.
- Stated production windows run from 4 weeks to 6 months, and none include permitting, which is a separate clock run by your city.
- A company that publishes nothing is not necessarily worse. It is a company you cannot compare before a sales call.
The finding, in one chart
Of 14 California prefab ADU sellers checked on 31 August 2026. Two further companies did not respond to our requests and are excluded from the counts rather than counted as failing.
What does each company actually publish?
| Company | Size range | Published figures | What the price covers | Timeline |
|---|---|---|---|---|
| Abodu Best for knowing the whole number | 195 to 800 sq ft | $204,800 – $498,800 | Turnkey, with a written list of exceptions | 9 to 12 months, signing to keys |
| US Modular Best for a single responsible party | 150 to 951 sq ft | $40,000 – $689,500 | Turnkey to certificate of occupancy | 1 to 3 months |
| Boxabl Best for the lowest headline price | 361 to 722 sq ft | $60,000 – $210,000 | Install included, per the company | about 2 months |
| Studio Shed Best for small builds and speed | 240 to 682 sq ft | $108,651 – $191,523 | Unit only, and it says so | 4 weeks to build, 2 to 3 to install |
| Samara Best for design | 150 to 950 sq ft | $147,000 – $781,246 | Not stated | 4 to 6 months |
| Perpetual Homes Best for a managed build | 200 to 1,173 sq ft | $15,000 – $900,000 | Managed end to end, not itemised | 3 to 4 months |
| LiveLarge Best for fast install | 350 to 1,190 sq ft | $40,000 – $360,000 | Billed separately, confirmed only via tax | 4 to 6 weeks |
| H2 Prefab Best for Bay Area delivery | 168 to 900 sq ft | $189,000 – $529,000 | Not stated | about 60 days |
| Connect Homes Best for compact footprints | 320 to 400 sq ft | $25,000 – $160,000 | Not stated | Not published, 23 pages read |
| Mighty Small Homes Best for kit buyers | 192 to 1,500 sq ft | $25,213 – $53,500 (kit) | Shell kit only | about 6 weeks |
| Crest Backyard Homes Best California-only focus | 222 to 1,200 sq ft | $100,000 (one figure only) | Warns about it without pricing it | Not published, 55 pages read |
| prefabADU Best for a fast quoted window | 150 to 2,124 sq ft | Nothing published, 13 pages read | Not stated | 4 to 8 weeks |
| Cover Quote only, nothing published | Nothing published, 43 pages read | Nothing published, 43 pages read | Not stated | Nothing published, 43 pages read |
| Den Sells plans, not buildings | Nothing published, site unreadable | Nothing published, site unreadable | Not applicable, plans only | Nothing published, site unreadable |
| Villa Homes did not respond to our requests | Excluded from the counts, not counted as a failure | |||
| Anchored Tiny Homes did not respond to our requests | Excluded from the counts, not counted as a failure | |||
How to read the figures column. These are the numbers each company publishes across its own model and pricing pages, crawled on 31 August 2026. They are the span of what a company shows, not a quote and not the price of any one unit. A low figure may be a small studio and a high one a two-bedroom. The point of the column is whether a homeowner can see a number at all before a sales call, not what that number buys.
Which company fits which situation?
3 ADU builders, editor-screened. 4 questions.
See my 3 matchesThe base price carries permits and plan check, foundation and site work, utility trenching up to 50 feet, connections, civil engineering and a project manager. Everything outside that is published by name.
- Permits, foundation, trenching to 50 ft and connections inside the price
- Publishes a written list of what is quoted separately
- A full signing-to-keys window
- Among the highest published figures here
- Trenching beyond 50 ft and craning beyond 100 ft are extra, and many lots need both
Design, permits, site work, utilities and installation run to the certificate of occupancy under one contract. Transportation, foundation and utility costs are named as separate lines on top of the home itself.
- One accountable party from design to occupancy
- Names transportation, foundation and utilities as separate lines
- Widest published range in the set
- Turnkey pricing is harder to compare against a unit price
The lowest headline unit price in the category, and installation covers engineering prints, permits, site prep, grading, foundation and water, waste and power hookups.
- Lowest headline unit price in the set
- Install covers permits, grading, foundation and hookups
- California delivery is not clearly stated
- Site work also appears inside a financing disclaimer
The clearest of the unit-only sellers. Assemblers quote site work separately, and permit fees are the homeowner's responsibility.
- Fastest stated production window here
- States plainly that site work and permits are not in the price
- Unit only, so the published price is not the project price
- Does not estimate what site work costs
A clear price ladder and a production window, and site preparation takes 4 to 6 weeks. What that preparation costs, and who pays for it, never appears.
- Clear published price ladder
- Both a build window and a site-prep window
- Times site work but never prices it
- Silent on what the published figure covers
The project runs from site inspection and permits through site preparation, construction and utility connections under one roof. The company also advertises no markup on site work.
- Manages permits, site prep and utility connections
- A 7-year warranty, the only one in the set
- Advertises no markup on site work
- Published range is so wide it is hard to read as a price
- No itemisation of what is inside the number
A 4 to 6 week window, and site work is billed separately. That last fact surfaces only inside an answer about which costs carry sales tax.
- Fastest stated window in the set
- Site work is a separate line
- Never prices site work
- Discloses it only inside a tax answer
A full price ladder, a size range and a delivery window, with the Bay Area as the service area. What the price covers never appears.
- Bay Area focus
- Full price ladder and a stated window
- Silent on what the price covers
A price ladder across the compact units, and nothing across 23 pages about what the figure covers or how long it takes.
- Published price ladder
- Compact footprints suited to tight lots
- Silent on site work
- No published timeline across 23 pages
A panelised shell kit rather than a finished unit, which is why the figures sit an order of magnitude below the delivered sellers.
- Lowest published figures in the set
- Widest size range published
- A production window
- A kit, not a finished building
- Everything after the shell is the buyer's cost
A California-only operator that warns readers local agencies often require separate utilities for an ADU, then publishes a single figure and no timeline across 55 pages.
- California-only focus
- Warns about separate utility requirements
- One published figure across the whole site
- No timeline published across 55 pages
A production window and the widest size range in the set, and no pricing at all.
- A 4 to 8 week window
- Widest published size range
- No published pricing
- Silent on what a quote covers
A design-led studio. We read 43 pages and found no price, no size range and no timeline. Every number in this category sits behind a sales call.
- Design-led approach
- Nothing a buyer can compare before a call, across 43 pages
Architectural plans rather than a delivered building, so a different product from everything else here. Only one page of the site could be read at all.
- A different model, plans rather than units
- Not comparable to a delivered ADU
- Site returned a single readable page
What does the sticker price leave out?
Abodu is the only manufacturer in the set that tells a homeowner, in writing and before a sales call, what sits outside the quoted price. From its pricing page, verbatim:
"What's Quoted Separately? A flat $6,000 boundary survey, foundation staking, and certification package; trenching beyond 50 feet; craning beyond 100 feet; demolition or tree removal; unique site engineering; and sales tax."
Read that list again as a budget. Trenching beyond 50 feet. Craning beyond 100 feet. Tree removal. Those are not exotic conditions in a California backyard, they are the normal condition of one. A unit placed behind a house on a narrow lot is routinely more than 50 feet from the nearest sewer connection and more than 100 feet from anywhere a crane can stand.
Studio Shed states the principle without the list: assemblers quote site work separately, and permit fees are the homeowner's responsibility. LiveLarge discloses it only in the context of tax. Boxabl and US Modular go the other way and fold installation, permits, grading, foundation and hookups into the number.
The exclusions are not a footnote, they are the variable. Every item on that list is a site condition, and site conditions are the part of an ADU budget that no website can quote. Two identical units, same model and same finish, land at different totals because one backyard has a sewer connection at the property line and the other has it under the driveway. The unit is the fixed part of the project. The exclusion list is the part that moves, and six of the fourteen companies here say nothing at all about what their figure covers.
That makes the flat items worth reading first. Abodu's boundary survey is quoted as a flat charge, which makes it the one exclusion a homeowner can add to the sticker price before anyone has visited the site. The rest are conditional, and the conditions are written as distances. Beyond 50 feet of trenching. Beyond 100 feet of craning. A homeowner who wants a real number before the sales call can walk those two distances in an afternoon and know which side of the line their yard sits on. Nothing else in this set gives a buyer that much before a deposit.
Boxabl and US Modular are making the opposite trade. A number that already contains installation, permits, grading, foundation and hookups is comparable to a builder's bid rather than to a unit price, and it carries the seller's assumption about the site rather than the buyer's. A single published price is easier to read and harder to check. A price with an exclusion list attached is harder to read and possible to check. Only one of the two can be tested against a specific backyard, and it is not the simpler one.
How did we check this?
We took the companies appearing in Google's California results for prefab ADU queries on 31 August 2026, then crawled each company's own website by following its own links, reading model, pricing, cost, FAQ, process and how-it-works pages, up to 55 pages per company.
- 16 companies in scope, 14 reachable
- 11 publish a price anywhere on their own site
- 12 publish a size range
- 10 publish a production window
- 8 say what the published figure covers
- 3 sell a finished project rather than a unit
What this does not tell you. It measures what a company publishes, not what it charges. A company that publishes nothing may quote fairly on a call. Absence from a website is not evidence of bad faith, it is evidence that a homeowner cannot compare before picking up the phone.
What we did not test: build quality, finish, warranty performance, or on-time delivery. We have no basis for those claims and we are not making them. And nothing can buy a place here: no company on this list has a commercial relationship with Renology.
The Renology Take
The easy conclusion is that the companies hiding their prices are the ones to avoid. The data does not support it. Two of the most respected names here, Samara and Cover, publish little or nothing, and their reason is defensible: a price without a site assessment is a number that will be wrong.
The real finding is worse and subtler. The problem is not silence, it is a published price with no stated boundary. Eleven companies publish a figure and only three sell a finished project. A homeowner comparing $53,500 against $498,800 is not comparing two prices, they are comparing a panelised shell kit against a turnkey building, and nothing on either website says so. For what the same project runs when it is built on site in Los Angeles, the comparison starts from a different number entirely. That gap is where this category's reputation is made.
Methodology
How Renology builds this guide
Renology combines public permit and labor signals, supplier pricing, remodeler quote patterns, and editorial review of comparable projects. Cost references are planning ranges, not fixed bids, because site conditions, materials, access, permits, and finish level can change the final price.
- Benchmarked against the Renology Cost Index, related service guides, and the Renology Methodology.
- Reviewed for local market context when a local market is available.
- Focused on ADU scope, materials, timeline, contractor risk, and budget drivers.
Frequently Asked Questions
Is a prefab ADU cheaper than site built in California?
What does site work actually include?
How long does a prefab ADU take in California?
Does a prefab ADU need the same permits as a site-built one?
Which prefab ADU company is cheapest?
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Sources
- Abodu, pricing and what is quoted separately· accessed 2026-08-31
- Studio Shed, frequently asked questions· accessed 2026-08-31
- Boxabl, installation and what it covers· accessed 2026-08-31
- US Modular, process and turnkey scope· accessed 2026-08-31
- California HCD, Accessory Dwelling Unit Handbook· accessed 2026-08-31
- California HCD, factory-built housing program· accessed 2026-08-31