Washington RCW 80.60.030: Meter Aggregation and March 31 True-Up Guide

Key Takeaways

• Washington State's RCW 80.60.030 governs net metering billing, meter aggregation, and credit expiration.
• Unused kilowatt-hour credits from the previous year expire annually on March 31st without compensation.
• Meter aggregation allows combining a designated meter with one additional contiguous parcel meter.
• The customer-generator is responsible for purchasing production meters and software for aggregation if required by the utility.

What are the key provisions of Washington RCW 80.60.030 for net metering?

Washington State's Revised Code of Washington (RCW) 80.60.030 outlines the specific rules for net metering billing calculations, multi-meter aggregation, and the annual expiration of unused credits. This statute ensures that electric utilities measure net electricity produced or consumed during each billing period according to normal metering practices (August 2026).

When you generate more electricity than you consume, the electric utility credits you for these excess kilowatt-hours. This credit appears on your bill for the following billing period, reducing your future electricity costs (August 2026). However, these credits do not roll over indefinitely. On March 31st of each calendar year, any remaining unused credits accumulated during the previous year are granted to the electric utility without compensation (August 2026). This annual "true-up" means you should aim to use your credits before this date.

How does meter aggregation work under RCW 80.60.030?

RCW 80.60.030 mandates that electric utilities must provide meter aggregation if a customer-generator requests it. This provision allows you to combine the billing for multiple meters under certain conditions. The credits earned by your net metering system are first used to offset electricity supplied by the utility at the location of your designated meter (August 2026).

You can aggregate a designated meter with one additional aggregated meter. This additional meter must be located on the same parcel as the designated meter or on a parcel that is contiguous with it (August 2026). For the purpose of this RCW, parcels are considered contiguous if they share a common property boundary, even if a road or rail corridor separates them (August 2026). It is important that the retail electric customer receiving service at the aggregated meter is the same retail electric customer as at the designated meter (August 2026).

If your electric utility requires a production meter and software to provide meter aggregation under RCW 80.60.030(4), you, as the customer-generator, are responsible for purchasing this equipment (August 2026).

Can multifamily residential facilities utilize net metering and aggregation?

Yes, RCW 80.60.030 includes provisions for multifamily residential facilities. The law explicitly states that nothing in this section prohibits the owner of a multifamily residential facility from installing a net metering system. This system must be assigned to a single designated meter located on the premises of the multifamily residential facility (August 2026). This allows property owners to benefit from solar generation across multiple units, provided the system is tied to one designated meter.

What is the impact of the March 31st credit expiration?

The annual expiration of unused kilowatt-hour credits on March 31st is a critical aspect of Washington's net metering policy. This means that any excess generation credits you have accumulated from the previous year will be reset to zero on this date, and the utility will absorb them without payment (August 2026). This provision encourages customer-generators to size their systems appropriately and to manage their energy consumption to maximize the use of their generated credits within the annual cycle.

Understanding this deadline is crucial for financial planning related to your solar investment. You may consider adjusting your energy usage patterns or system configuration to minimize the loss of credits. For more details on net metering capacity limits, you can consult our guide on Washington RCW 80.60.010 Solar Net Metering and Capacity Limits.

How we verified this information

We verified the information presented in this guide by directly consulting the official Washington State Legislature website on August 23, 2026. Our primary source was the Revised Code of Washington (RCW) 80.60.030, which directly outlines the statutory requirements and definitions for net metering, meter aggregation, and credit expiration. We also referenced RCW 80.60.020 for details on production meter responsibility. This approach ensures that the information provided is accurate and directly reflects current state law.

What are the implications for system design and financial planning?

The provisions of RCW 80.60.030 have direct implications for how you design your solar energy system and plan your finances. The March 31st true-up date means that over-sizing your system significantly could lead to uncompensated excess generation. You should aim to match your annual generation closely with your annual consumption to maximize the financial benefits of net metering.

Meter aggregation offers flexibility for properties with multiple meters or contiguous parcels, allowing for more efficient use of solar generation across different points of consumption. If you are considering a multi-meter setup, factor in the potential cost of a production meter and software, as this expense falls to the customer-generator (August 2026).

For a broader understanding of how state regulations impact solar installations, you may find our guides on Oregon PUC Level 1 Interconnection Guide and Pennsylvania PUC 52 PA Code 75.13 Solar Net Metering Guide helpful, though these cover different state-specific regulations. You can also use our solar sizing tool to estimate your energy needs and potential system size.