Why ADU utility work needs a property review
Water, sewer, electrical, and gas work cannot be priced responsibly from the ADU floor plan alone. A complete utility scope starts with the existing house, the route across the property, available capacity, and the requirements of the city and utility providers.
Two similar ADUs can need very different work when one sits near the existing services and the other requires long trenches, pavement repair, a panel upgrade, or a new sewer lateral. That is why Vision ADU verifies the property before issuing a written estimate.
Water service
The first decision is whether the ADU can use the main home's water service or needs separate metering.
- Shared service: Often uses the existing water connection, subject to pipe size, pressure, and local rules.
- Private submeter: Can help an owner track tenant use while keeping the utility account shared.
- Separate utility meter: May support independent billing or a future title strategy, but requires utility approval and additional site work.
The route also matters. The estimator should confirm the distance from the source, trench access, pipe sizing, backflow requirements, and any hardscape that must be removed and restored.
Sewer connection
Most ADUs connect to the property's existing sewer system, but the correct approach depends on elevation, pipe condition, capacity, and the route to the lateral.
Key questions include:
- Can the ADU drain by gravity?
- Is the existing lateral large enough and in serviceable condition?
- Does the route cross a driveway, patio, retaining wall, or landscaped area?
- Will the city or sanitation district require a cleanout, inspection, capacity review, or official connection fee?
- Is a new lateral to the public main necessary?
A camera inspection and site measurements can identify many of these conditions before construction begins.
Electrical service and panel capacity
California ADUs commonly use all-electric appliances, heat-pump HVAC, and heat-pump water heating. The electrical design should begin with a licensed load calculation for the main house and proposed ADU.
The resulting scope may include:
- A feeder and subpanel for the ADU
- A main-panel or service upgrade
- A separate meter when approved by the utility
- Trenching or overhead routing
- Coordination with required solar PV for qualifying new construction
- Space and capacity for future electric-vehicle charging
The best configuration depends on available amperage, equipment locations, utility standards, and the owner's billing or future-sale goals.
Gas service
Many new ADUs are designed without gas. An all-electric plan avoids a new gas route and supports modern heat-pump equipment. If gas is part of the design, the team must confirm meter capacity, pipe sizing, trenching, appliance venting, and current local code.
What changes the utility scope most
The largest variables are:
- Distance from the ADU to existing service points
- Condition and capacity of existing lines and panels
- Shared versus separate meters
- Trenching access and hardscape restoration
- Gravity sewer feasibility
- Utility-provider and jurisdiction requirements
- Solar, fire-zone, hillside, and title-separation goals
What your written estimate should include
A complete proposal should identify the assumed utility routes, meter strategy, known upgrades, trenching and restoration, utility coordination, official fees or allowances, exclusions, and conditions that require further investigation.
Avoid comparing proposals that use different assumptions. A low number may simply omit the panel, lateral, meter, trench, restoration, or provider coordination needed for the property.
Get a property-specific utility plan
Book a free site assessment so Vision ADU can review your service locations, panel, sewer route, meter goals, and jurisdiction requirements. We will define the utility scope and provide a property-specific written estimate instead of relying on a generic component price.
Related Vision ADU Resources
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- How to Build an ADU, Day 1: Architecture & Design
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- 2026 ADU Cost Calculator
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