When do I need to think about utility connection?

Utility connections can have significant design and scheduling impacts, so it’s good to think about them early on.

In general, it is less expensive to hook the ADU utilities to the main house, as opposed to building new water and sewer laterals to the mains in the street, or a second set of electrical lines from the pole. In some cases, particularly if your ADU is larger, over 750 sf, you may be required to construct new connections. It is best to discuss this issue with your jurisdiction early in the design process. This conversation may require talking to multiple departments to get a full understanding of the requirements. Start with the Planning Department, but make sure to also check with the Building Department, Public Works and/or your local water and sewer district offices.

Most homes will need to upgrade the main electrical panel and possibly electrical service to the property. This will involve both an electrician as well as coordinating with PG&E. Due to the demands on PG&E services, the upgrade process can take significant time and homeowners are often charged a $1,500 engineering fee for PG&E to begin the process. Additional fees may be charged depending on the condition and size of the electrical components running to the property. If your ADU will be detached or in a separate, converted building (such as a converted detached garage), PG&E requires the installation of a second electric meter.

Typical utility upgrades for an ADU include a main electrical panel of at least 200 Amps and a sewer lateral of 4" for the whole property. If the existing lateral is 3" you may have to replace it with a 4" lateral to the street to handle the additional demand created by the ADU. Please consult with your building department for more information.

Water service may need to be upgraded as well, particularly when sprinklers are required such as when an ADU is built above a garage. The scale and cost of this work depends greatly on the age of the main house and the infrastructure provided by jurisdiction. It is important to determine if sprinklers will need to be planned for and get information on the water supply to your property early in the design and bidding process. This information is typically available from your Public Works or Engineering Department.