MEP CA AB 1103

Challenges in Metering and Tracking Energy Efficiency

Understanding a building’s energy performance is critical when determining how energy moves within an onsite renewable energy system and the grid. Limited utility-provided data makes it difficult to benchmark energy performance since property managers only know net consumption but not how much energy their building is producing as opposed to using.

Assessing a building’s true energy use is necessary to assess their overall energy performance. Accurate benchmarking requires knowledge of the exact values of renewable energy generated onsite that was exported back to the grid (Rex), renewable energy generated onsite that was used onsite (Ru), and grid energy sent to the building (G). Since many meters provide limited information about the energy usage, it’s important to find the values elsewhere, through alternate meters.

Three types of metering dominate the way electric distribution utilities provide for their customers. As determined by local standards and policies, contractual agreements, and the building itself, these metering methods each have their own pros and cons.

Net meters

Most closely aligned with utility building systems, net meters spin forward and backward to show the net power consumption. While they don’t display what energy was imported and exported, these meters indicate the net difference (N), or the difference between the two.

Bi-directional meters

Meters that have 3 screens, bi-directional meters tell how much gird energy was imported (G) and how much renewable energy has been exported (Rex). The first of the three screens shows how much power has been delivered, the second shows how much power was received, and the third screen displays the net power going out to the grid. The exact setup for each bi-directional meter slightly varies.

Dual meters

Dual metering is a traditional usage meter that separately measures how much grid energy has been imported (G) and how much renewable energy was exported (Rex). Also called a production or generation meter, this type of meter is far less common than net meters or bi-directional meters.