As you research solar, you may be wondering if any modifications may be needed to your existing electrical service in order to support your new solar system.
When making the switch to solar, a new solar circuit will need to be added to your electrical service. When adding any new circuitry, the 120% rule of the National Electric Code (NEC) must be adhered to, which requires that solar systems are installed in panel boxes up to 120% of the busbar rating.
You will most likely not need a service upgrade if your existing panel box is already rated at 200A or more (however there are exceptions to this). If your panel box rating is less than 200A, you likely will need a panel box upgrade, but this will also depend on your solar system's capacity.
Even if your solar system capacity can be supported on a 100A busbar for example, you may still want to consider an upgrade for future-proofing (for instance if you have plans of adding an EV charger or a new electrical appliance to your home).
If a panel box upgrade is required, the pricing will vary depending on the specific scope of work required and whether your local utility company grants approval for the upgrade to take place in the same location of the existing service, or a new one. In most cases, the same location is approved if there are no pre-existing code violations with the current setup.
Examples of code violations that may call for relocation include:
⁃ Panel box facing the street
⁃ Gas meter or gas lines are less than 36" away from the service
⁃ For overhead services: no clear ladder access to the roof
During your project, OneSun will order a meter spot from your local utility company to determine the appropriate location and scope of work.
A common question homeowners ask is if a panel box upgrade can be avoided. Here are some scenarios in which this is possible:
1. Most common: Derate the main breaker (typically applies to 200A busbar services)
This option is much cheaper than upgrading your panel box, as this scenario simply requires us to replace your main breaker only, not the entire service. For instance, on a 200A busbar panel box that also has a 200A main breaker, the maximum solar circuit size that is allowable by code is 40A. If you need a 60A solar breaker, all we would need to do is swap out your 200A breaker with a 175A breaker to stay in compliance with the National Electric Code's 120% rule.
2. Line side tap (uncommon): In this scenario, the solar connection will be made on the busbar (utility side) of the service disconnect. This is not allowed by most jurisdictions, but exceptions are sometimes made.
3. GMA (Generation Meter Adapter): This scenario applies to SCE territory only, not LADWP, BWP, GWP, or PWP. SCE offers this option for residential services rated up to 200A. A GMA device can be installed on a meter socket and allow for the solar to connect to the load side of the service without the need for a panel box upgrade. SCE currently charges a $500 service fee for this. While it is less expensive than a service upgrade, your future plans for the home should be taken into account. For example, if you currently have a 100A service and decide to interconnect your solar system with a GMA but need to upgrade your panel box in the future anyway for a new HVAC unit or EV charger, it will be better to do the upgrade within the solar project so you will pay less overall. It is also worth noting that having a GMA in your project scope of work will increase the project turnaround time by at least a couple months, as SCE tends to be slow in processing this type of request.
4. Reducing PV capacity to stay within limits of existing service (least recommended option): While this will save some money on your solar project short-term, you may compromise the return on your solar investment long term by limiting your PV capacity. Of course there is never a one-size-fits-all right or wrong approach, so it will be best for us to evaluate your overall goals and expectations first.
Every property and every situation is unique. Upon completing a property assessment, OneSun will advise on the best approach for your needs. Contact us today to learn more and get your free estimate.
877-662-0116