One of the biggest questions that seems to be confusing electricians and even meter techs alike these days are how to handle the metering of a solar power installation. The physical connections have confused many electricians that I have dealt with in the past. Many people also do not realize that the solar meter can actually be a regular meter. Because of this I thought I would post up this solar metering wiring diagram for a simple solar metering installation. There are also large scale solar projects that are being built. If you want to know more about those visit: Understanding Utility-Scale Solar Generation and Its Integration into the Grid.
It may be a bit difficult to see but the original meter base from the house is NOT changed. The most common way to do this is to install a trough either above or below the meter base to make the connections in. This diagram shows an underground installation. As you can see in the solar meter base the wiring actually looks backwards. The wires in the top terminal go out to the solar panels and the wires on the bottom terminals go back and tie in to the utility.
A fused disconnect is always used and goes out to the solar panels.
Wiring diagram of a typical residential solar metering installation.
This type of metering is for a buy all sell all metering agreement between the customer and the utility. Many people are unaware that the utility has different rate structures for different solar power installations. In this type of solar power metering installation the utility sells all of the power that the customer uses to the customer at the normal rate. The utility also buys back all of the power that the customer generates at the rate determined by the utility.
Now, the buyback rate from the utility is typically close to the wholesale rate that the utility pays to buy or produce its power.
Another type of solar power metering is called bidirectional metering. In this type of solar panel metering installation one meter is used and it takes the amount of kwh used by the customer and subtracts from it the amount of kwh generated by the solar panels. Another name for this type of metering installation is called net metering. This is typically favored by customers because they are able to trade kwh for kwh. However, many utilities do not offer this type of metering installation.