Should You Budget for Separate Utility Hookups on Your ADU?

Understanding Utility Hookup Requirements for Your ADU

Utility connections are one of the most significant variable costs in an ADU project, yet they are also one of the least understood. Whether you need separate utility hookups or can tie into your existing services depends on your ADU size, your local jurisdiction, and the current capacity of your property's utilities. Getting this wrong can mean budget overruns of $10,000 to $30,000 or more.

In this guide, we will cover every utility type, explain when separate connections are required versus when shared connections are allowed, and provide realistic cost estimates to help you budget accurately. Whether you are planning a small studio ADU or a full two-bedroom unit, this information will help you understand what to expect.

What California Law Says About ADU Utility Connections

California's ADU laws include important protections for homeowners regarding utility connections:

ADUs Under 750 Square Feet

For ADUs under 750 square feet, California Government Code Section 65852.2 prohibits local agencies from requiring new water or sewer connections and from charging connection fees. This is a significant cost savings and one of the reasons smaller ADUs are often more economically feasible.

ADUs 750 Square Feet and Larger

For ADUs of 750 square feet or more, local jurisdictions may require separate utility connections and charge applicable connection fees. However, the fees must be proportionate to the burden of the ADU on the utility system, and they must be calculated on a per-square-foot basis rather than a flat rate equivalent to a single-family home.

Key Legal Provisions

ADU Size	Connection Fees	Separate Connection Required?
Under 750 sq ft	Prohibited	No (must allow shared)
750 sq ft and larger	Proportional fees allowed	May be required by local rules
JADU (up to 500 sq ft)	Prohibited	No (within existing structure)

Water Service and Hookup Costs

Shared Water Connection

In most cases, your ADU can share the existing water service with your main house. This involves branching a new water line from the existing service to the ADU. Requirements typically include:

• A new water line from the existing service (or main house plumbing) to the ADU
• A backflow prevention device (required by most jurisdictions)
• Adequate water pressure at the ADU location

Cost for shared connection: $1,500 to $5,000 depending on distance and trenching conditions

Separate Water Connection

A separate water connection involves installing a new water meter and service line from the city water main to your ADU. This is more expensive but may be required for larger ADUs or preferred for rental units where you want separate billing.

Cost for separate connection: $5,000 to $15,000 including meter, service line, and connection fees

Sewer Connection Options and Costs

Sewer connections are often the most expensive utility hookup for ADU projects. The cost depends heavily on whether you can tie into your existing sewer lateral or need a new connection.

Shared Sewer Connection

Tying into your existing sewer lateral is the most cost-effective option. This involves running a new drain line from the ADU to your existing sewer cleanout or main drain line.

Cost: $2,000 to $6,000

Separate Sewer Lateral

Some cities require a separate sewer lateral for the ADU, which means running a new pipe from the ADU all the way to the city sewer main in the street. This is the most expensive scenario and can involve street excavation and restoration. For a detailed breakdown, see our guide on sewer lateral connection costs for ADUs.

Cost: $5,000 to $25,000+

Sewer Cost Factors

Factor	Impact on Cost	Typical Range
Distance to sewer main	High	$100 to $200 per linear foot
Street restoration	High	$3,000 to $10,000
Depth of sewer main	Moderate	Deeper = more expensive
Permits and inspections	Moderate	$500 to $2,000
Video inspection	Low	$200 to $500

Electrical Service and Panel Requirements

Shared Electrical Service

Most ADUs are connected to the main house's electrical system through a sub-panel. This is the most common and cost-effective approach. The sub-panel is typically 60 to 100 amps, depending on the ADU's electrical load.

Cost: $2,000 to $5,000 for sub-panel and wiring to the ADU

Panel Upgrade

If your main house has a 100-amp panel (common in homes built before the 1980s), it likely cannot support the additional load of an ADU. An upgrade to a 200-amp main panel is usually required. Learn more about electrical requirements in our guide to ADU electrical requirements.

Cost: $2,000 to $5,000 for panel upgrade

Separate Electric Meter

A separate electric meter allows independent billing for the ADU, which is advantageous for rental units. This requires coordination with your utility company (LADWP, SCE, PG&E, etc.) and may involve a new service drop from the transformer.

Cost: $3,000 to $8,000

Gas Service Considerations

Do You Need Gas for Your ADU?

With California's push toward electrification and the availability of efficient heat pump water heaters, induction cooktops, and mini-split HVAC systems, many ADUs are being designed as all-electric. This eliminates the need (and cost) of gas service entirely.

Benefits of all-electric ADU design:

• No gas line extension costs ($1,000 to $4,000 saved)
• No gas meter fee ($0 to $500 saved)
• Potential utility rebates for all-electric construction
• Compliance with future electrification mandates
• Lower carbon footprint

If Gas Is Desired

If you choose to include gas appliances, you will need a gas line extended from your existing meter to the ADU.

Cost: $1,500 to $4,000 for gas line extension

For a comprehensive look at HVAC options including all-electric systems, read our ADU HVAC guide.

Complete Utility Cost Summary Table

Utility Type	Shared Connection	Separate Connection
Water	$1,500 to $5,000	$5,000 to $15,000
Sewer	$2,000 to $6,000	$5,000 to $25,000
Electrical (sub-panel)	$2,000 to $5,000	$3,000 to $8,000
Electrical Panel Upgrade	$2,000 to $5,000	N/A (included in separate meter)
Gas	$1,500 to $4,000	$3,000 to $6,000
Telecom / Internet	$200 to $500	$500 to $1,500
Total (Shared)	$9,200 to $25,500
Total (Separate)		$16,500 to $55,500

When to Choose Shared vs. Separate Utilities

Choose Shared When:

• Your ADU is under 750 square feet (required by state law to allow shared)
• You plan to use the ADU for family members and do not need separate billing
• Your existing utilities have adequate capacity
• You want to minimize upfront costs

Choose Separate When:

• You plan to rent the ADU and want tenants to pay their own utilities
• Your existing panel or water service is at capacity
• Your city requires separate connections for ADUs over a certain size
• You want maximum flexibility for future use or sale

Utility Planning Tips

1. Contact utility providers early: Get capacity assessments and cost estimates from your water, sewer, electric, and gas providers before finalizing your ADU design
2. Consider all-electric: Eliminating gas service simplifies connections and can save $1,500 to $4,000
3. Factor in trenching costs: The distance between your ADU and existing utility connections significantly affects cost. Longer runs through existing landscaping or hardscape cost more
4. Coordinate utility work: Having all utility trenching done at the same time reduces excavation and restoration costs
5. Check for rebates: Utility companies offer rebates for energy-efficient appliances and all-electric construction that can offset hookup costs

Conclusion

Utility hookup costs can range from as little as $5,000 for a small ADU with shared connections to over $40,000 for a larger ADU requiring separate water, sewer, and electrical services. The key to managing these costs is understanding your options early, working with your local utility providers to determine what is required, and designing your ADU to minimize utility infrastructure costs.

For most homeowners building ADUs under 750 square feet, shared utility connections offer the most cost-effective path. For larger ADUs or rental units, separate connections may be worthwhile despite the higher upfront cost because they provide billing flexibility and eliminate shared capacity concerns.

When Shared Utilities Make Sense vs. Separate Hookups

One of the most important financial and practical decisions in ADU planning is whether to share utility connections with the main house or install separate hookups. The right answer depends on your specific situation, how you plan to use the ADU, and your local utility company's requirements.

When Shared Utilities Are the Better Choice

Sharing utility connections with the main house makes sense in these situations:

• Family use: If the ADU is for a family member and you are not concerned about separating utility costs, shared connections save on upfront installation costs
• Budget constraints: Shared utilities can save $8,000 to $20,000 compared to separate hookups, which can make or break a tight project budget
• Short-distance connections: When the ADU is close to the main house (within 30 feet), running utility lines from the existing systems is typically straightforward and affordable
• Lower utility demand: A small studio ADU (under 500 square feet) used by one or two people may not generate enough utility usage to justify the cost of separate meters and hookups
• Cities that allow shared connections: Some jurisdictions actively encourage shared utility connections for ADUs to reduce infrastructure strain and permitting complexity

When Separate Hookups Are Worth the Investment

Separate utility connections make more financial and practical sense in these scenarios:

• Rental income: If you plan to rent the ADU, separate meters allow tenants to pay their own utility bills, which simplifies your landlord responsibilities and reduces disputes
• Existing capacity limitations: If your main house's electrical panel, water meter, or gas line is already near capacity, separate hookups may be required rather than optional
• Long-distance runs: If the ADU is far from the main house (more than 50 feet), running separate service lines from the street may actually be more cost-effective than extending the main house's systems
• Future property sale: Separate utilities increase the ADU's value as an independent unit and can make the property more attractive to buyers who want rental income potential
• Utility company requirements: Some utility companies require separate meters for ADUs that have full kitchens or that exceed a certain size threshold

Tips for Working with Utility Companies

Utility companies are essential partners in your ADU project, but they operate on their own timelines and processes. Here is how to work with them effectively.

Start Early

Contact your gas, electric, and water utility providers as soon as you begin the design phase. Utility companies often have lead times of 4 to 12 weeks for new service installations, capacity assessments, and meter installations. Starting these conversations early prevents utility work from becoming the bottleneck that delays your entire project.

Key Contacts for Los Angeles Homeowners

Utility	Provider (City of LA)	What to Request
Electricity	LADWP	Panel upgrade assessment, new service if separate meter needed
Water	LADWP	Meter capacity check, new meter application if separate
Gas	SoCalGas	Gas line capacity assessment, new service application
Sewer	LA Bureau of Sanitation	Sewer connection permit, lateral assessment

Document Everything

Keep records of every conversation, email, and confirmation number from your utility company interactions. Utility companies are large organizations, and information can get lost between departments. Written documentation protects you from scheduling mix-ups and ensures you have a paper trail if disputes arise about service dates or costs.

Ask About Fees Upfront

Utility connection fees can be substantial and vary widely between providers and service types. Get written fee estimates before committing to separate or shared hookups. Common fees include meter installation ($500 to $2,000), service line installation ($2,000 to $8,000), capacity upgrade charges ($1,000 to $5,000), and inspection fees ($100 to $500). These costs factor into your decision about shared versus separate utilities.

Frequently Asked Questions: ADU Utility Hookups

Does California law require separate utility meters for ADUs?

California law does not require separate utility meters for ADUs in most cases. AB 68 specifically prohibits cities from requiring separate utility connections as a condition of ADU approval if the ADU connects to the existing infrastructure. However, your utility company may have its own policies, and separate meters may be required if the existing service lacks capacity. Some homeowners choose separate meters voluntarily for billing convenience.

How much does a separate electrical panel cost for an ADU?

Installing a separate electrical sub-panel for your ADU typically costs $1,500 to $3,000 for a 100-amp panel, including the panel, breakers, and basic wiring from the main panel. If you need a full service upgrade to the main house (for example, upgrading from 100 amps to 200 amps) to accommodate the additional load, that can cost $3,000 to $6,000 additional. A completely separate electrical service from the street with its own meter adds $5,000 to $12,000 depending on the distance and LADWP requirements.

Can I add solar panels to offset ADU utility costs?

Yes, and many California homeowners do. Solar panels on the ADU or main house can offset electricity costs for both units. Under current California net metering policies, you can generate credits during the day and use them at night. For ADUs designed for rental income, solar can be a strong selling point for tenants. Check our article on whether you need solar panels on your ADU for current requirements and incentives.

What is the cheapest utility to install separately?

Gas is typically the least expensive utility to install separately because gas line extensions are relatively simple and SoCalGas often covers a portion of the installation cost for new service connections. A separate gas line from the existing meter to the ADU usually costs $1,500 to $3,000. By contrast, separate water and sewer connections are among the most expensive due to trenching requirements and city permit fees. For sewer-specific costs, see our detailed guide on sewer lateral connection costs for ADUs.

Do I need separate utility hookups for a JADU?

Junior ADUs (JADUs) are part of the existing house structure and almost never require separate utility hookups. Since JADUs share at least one wall with the main house and are limited to 500 square feet, they tap into the existing electrical, plumbing, and gas systems. This is one of the key advantages of a JADU over a full ADU from a cost perspective. The main consideration is whether your existing electrical panel and water heater can handle the additional load.

How do I handle utility billing if I share connections with a rental ADU?

If you share utility connections with a rental ADU, you have several billing options. You can include utilities in the rent price (simplest but requires estimating usage accurately), install sub-meters that measure the ADU's usage separately (allows you to bill the tenant for actual usage), or split the bill based on an agreed formula (such as square footage ratio). Check California tenant law regarding utility billing requirements, as there are specific rules about how landlords can pass utility costs to tenants. Including utilities in the rent is the most common approach for ADU landlords in Los Angeles.

Will separate utility hookups increase my property taxes?

Separate utility hookups themselves do not directly trigger a property tax reassessment. However, the completed ADU as a whole will likely increase your assessed property value, which can raise your property taxes. The increase is based on the value the ADU adds to the property, not specifically on the utility configuration. In California, Proposition 13 limits annual assessment increases to 2 percent, but new construction (including ADUs) is assessed at current market value when completed. For a broader look at ADU financial considerations, review our article on ADU investment and ROI in Los Angeles.