Off-Grid Solar Requirements

• Systems shall be designed by an Electrical Engineer
• Systems shall be designed to provide sufficient power for all expected loads which may include well, fire alarms, and sprinkler pumps. Load calculations and other required information is needed to determine compliance.
• Systems shall provide 3 days of autonomy.
• Systems shall include a fixed generator controlled by an automatic transfer switch.
• Systems shall be approved by the local fire district.

• Systems shall be designed based on daily winter electrical usage.
• Solar array output rating shall be minimum 50% of the winter daily kWh (expressed in kW) adjusted using a shading factor when trees or other obstructions limit solar access.
• Minimum battery inverter capacity: The inverter shall be rated to meet the maximum surge load and the maximum continuous loads calculated.
• Minimum battery capacity shall provide 3 days of autonomy – The battery bank shall be approved based on available capacity (kWh).
• A generator plug socket and designated portable generator location with gravel and/or solid pad is required. A fixed generator with an auto-start feature is optional.

• Load calculation based on the example included below. · Solar plans per the Solar (PV) & Battery Permits submittal guide · Generator plans per the Generator submittal guide or fixed automatic transfer switch type generator.
• For portable generators indicate the location of the required gravel and/or solid pad, submit a generator specification sheet, and specifications for the manual transfer switch.
• Shading report which indicates the available solar access and is used to adjust the solar array output.
• Battery specification sheets including the discharge capacity.

The California Residential Code defines a dwelling unit as “a single unit providing complete independent living facilities for one or more persons, including permanent provisions for living, sleeping, eating, cooking and sanitation”. The California Electrical Code requires a minimum 100-amp electrical service and separate electrical circuits for kitchen countertops, bathrooms, laundry rooms and exterior receptables. In order to meet these minimum code requirements, it has been established 4kWh as the minimum daily winter load used for the design of off-grid systems. We recognize that members of our community may use less power and must balance this with the minimum standards listed above. It is our hope that the additional electrical capacity will provide a comfortable and usable residence for the life of the structure while not increasing the cost of the system excessively.

The minimum system design criteria is as follows:

• Winter Electrical Usage: 4kWh
• Minimum Solar Array: 2kW adjusted for shading
• Minimum Battery Storage: 12kWh based on available usable storage capacity
• Minimum Inverter Rating: 7kw

Step 1: Calculate your winter daily consumption.

Identify all applicable loads from the list on Typical Loads for Residential Off-grid Solar Design. Add all daily loads to determine the total daily winter consumption – see Winter Daily Consumption Example below.

Step 2: Determine the solar array output.

The solar array shall be greater than 50% of average daily kWh expressed in kW and shall be adjusted using a shading factor (% available average September-March).

Example: Home has 8 average kWh daily usage, and the shading report shows 75% average sun through dark half of the year.
Calculation: 8.0 kWh x .5= 4 kWh array size/.75 average shading= 5.33 kW minimum DC rating for solar array.

Step 3: Determine the required battery bank kWh capacity based on a minimum 3 days of autonomy and the available battery storage capacity based on battery type/chemistry and charge controller settings.

Example: Total daily winter consumption x 3 days of autonomy / maximum battery discharge = battery bank capacity.
Calculation: Total Daily Consumption: 8 kWh x 3 Days Autonomy =24 kWh/.75 maximum battery discharge = 32 kWh.

Winter Daily Consumption Example