Perspectives and practices in PV metering


Washington, DC, U.S.A. — (METERING.COM) — March 12, 2008 – Utilities are generally accommodating the interconnection and net metering of residential solar photovoltaic (PV) projects using existing systems, but the existing billing systems generally cannot accommodate net metered customers easily.

These are among the findings of a new survey on grid-connected PV metering and interconnection practices released by the Solar Electric Power Association (SEPA). Sixty-three U.S. utilities representing a cross section of utility types and geographic diversity participated in the survey, which was aimed at establishing a baseline of utility best practices in grid-connected PV.

The survey found that there were few problems with reading meters. Most utilities also do not require a second meter for net metered PV installations and those that do require the second meter to record the total PV system output for performance, incentive or renewable energy credit verification. The cost of the second meter also varied, depending on whether the utility or the owner was responsible for the equipment and installation costs.

Interconnection standards for PV appear to be converging around the IEEE 1547 standard, with over 60 percent of utility respondents indicating as such. While most utility respondents require a final inspection for residential PV installations the trend among the most solar integrated utilities is to relax this if certain information and equipment parameters are met. A majority also do not require liability insurance. Processing times averaged one month, but interconnection delays were occurring outside the utility’s jurisdiction, with the most significant being incomplete documentation from customers and changes due to incorrect installation.

More than half of the utilities utilize only one or two documents to complete the net metering interconnection process and in most cases the interconnection agreement is less than 10 pages. Less than a quarter charge a fee for the process.

The standardization of both the requirements and the documentation could serve to streamline the interconnection process, suggest the SEPA. The decision by utilities to deploy new infrastructure, such as billing software or upgrades, second meters, etc., should also be balanced against the intent to reduce transaction costs. While net metered accounts represent a small number of the overall customer base, manually managing these accounts will become less feasible as the number of PV systems moves from tens to hundreds and thousands.

Most utilities are also either planning to deploy or are in the process of deploying smart metering technology. While smart metering can generally accommodate net metering, the technology and accounting/billing upgrades during this process should be compatible to avoid fixes later.

The number of grid-tied PV installations in the U.S. is small but growing, with the number of new systems approaching 10,000 in 2006, up 60 percent from the previous year, and with this growth likely to continue in the coming years with rising electricity prices, dropping PV system costs and growing interest in clean energy alternatives. Only seven of the responding utilities – four investor-owned and three municipal – had 500 or more residential PV systems currently installed and together these accounted for approximately 29,000 of the 101,500 systems nationwide.