Can I Connect Wind Turbine to the Utility Grid?

Small wind energy systems can be connected to the electricity distribution system and are called gridconnected systems. A grid-connected wind turbine can reduce your consumption of utility-supplied electricity for lighting, appliances, and electric heat. If the turbine cannot deliver the amount of energy you need, the utility makes up the difference.

When the wind system produces more electricity than the household requires, the excess is sent or sold to the utility.

Grid-connected systems can be practical if the following conditions exist:

• You live in an area with average annual wind speed of at least 10 mph (4.5 m/s).
• Utility-supplied electricity is expensive in your area (about 10 to 15 cents per kilowatt-hour).
• The utility’s requirements for connecting your system to its grid are not prohibitively expensive.
• There are good incentives for the sale of excess electricity or for the purchase of wind turbines.

Federal regulations (specifically, the Public Utility Regulatory Policies Act of 1978, or PURPA) require utilities to connect with and purchase power from small wind energy systems. However, you should contact your utility before connecting to their distribution lines to address any power quality and safety concerns. Your utility can provide you with a list of requirements for connecting your system to the grid. The American Wind Energy Association is another good source for information on utility interconnection requirements.

The following information about utility grid connection requirements was taken from AWEA’s Web site.

Net Metering

The concept of net metering programs is to allow the electric meters of customers with generating facilities to turn backwards when their generators are producing more energy than the customers’ demand.

Net metering allows customers to use their generation to offset their consumption over the entire billing period, not just instantaneously. This offset would enable customers with generating facilities to receive retail prices for more of the electricity they generate. Net metering varies by state and by utility company, depending on whether net metering was legislated or directed by the Public Utility Commission.

Net metering programs all specify a way to handle the net excess generation (NEG) in terms of payment for electricity and/or length of time allowed for NEG credit. If the net metering requirements define NEG on a monthly basis, the consumer can only get credit for their excess that month. But if the net metering rules allow for annual NEG, the NEG credit can be carried for up to a year.

Most of North America gets more wind in the winter than in the summer. For people using wind energy to displace a large load in the summer like air-conditioning or irrigation water pumping, having an annual NEG credit allows them to produce NEG in the winter and be credited in the summer.

Safety Requirements

Whether or not your wind turbine is connected to the utility grid, the installation and operation of the wind turbine is probably subject to the electrical codes that your local government (city or county) or in some instances your state government has in place.

The government’s principal concern is with the safety of the facility, so these code requirements emphasize proper wiring and installation, and the use of components that have been certified for fire and electrical safety by approved testing laboratories, such as Underwriters Laboratories. Most local electrical codes requirements are based on the National Electrical Code (NEC), which is published by the National Fire Protection Association. As of 1999, the latest version of the NEC did not have any sections specific to the installation of wind energy facilities, consequently wind energy installations are governed by the generic provisions of the NEC.

If your wind turbine is connected to the local utility grid so that any of the power produced by your wind turbine is delivered to the grid, then your utility also has legitimate concerns about safety and power quality that need to be addressed.

The utility’s principal concern is that your wind turbine automatically stops delivering any electricity to its power lines during a power outage. Otherwise line workers and the public, thinking that the line is “dead,” might not take normal precautions and might be hurt or even killed by the power from your turbine. Another concern among utilities is that the power from your facility synchronize properly with the utility grid, and that it match the utility’s own power in terms of voltage, frequency, and power quality.

A few years ago, some state governments started developing new standardized interconnection requirements for small renewable energy generating facilities (including wind turbines).

In most cases the new requirements have been based on consensus- based standards and testing procedures developed by independent third-party authorities, such as the Institute of Electrical and Electronic Engineers and Underwriters Laboratories.

Interconnection Requirements

Most utilities and other electricity providers require you to enter into a formal agreement with them before you interconnect your wind turbine with the utility grid. In states that have retail competition for electricity service (e.g., your utility operates the local wires, but you have a choice of electricity provider) you may have to sign a separate agreement with each company.

Usually these agreements are written by the utility or the electricity provider. In the case of private (investor-owned) utilities, the terms and conditions in these agreements must be reviewed and approved by state regulatory authorities.

Insurance

Some utilities require small wind turbine owners to maintain liability insurance in amounts of $1 million or more. Utilities consider these requirements are necessary to protect them from liability for facilities they do not own and have no control over. Others consider the insurance requirements excessive and unduly burdensome, making wind energy uneconomic. In the 21 years since utilities have been required to allow small wind systems to interconnect with the grid there has never been a liability claim, let alone a monetary award, relating to electrical safety. In six states (California, Maryland, Nevada, Oklahoma, Oregon, and Washington), laws or regulatory authorities prohibit utilities from imposing any insurance requirements on small wind systems that qualify for “net metering.”

In at least three other states (Idaho, New York, Virginia) regulatory authorities have allowed utilities to impose insurance requirements, but have reduced the required coverage amounts to levels consistent with conventional residential or commercial insurance policies (e.g., $100,000 to $300,000).

If your insurance amounts seem excessive, you can ask for a reconsideration from regulatory authorities (in the case of private investor-owned utilities) or to the utility’s governing board (in the case of publicly-owned utilities).

Indemnification

An indemnity is an agreement between two parties where one agrees to secure the other against loss or damage arising from some act or some assumed responsibility. In the context of customer-owned generating facilities, utilities often want customers to indemnify them for any potential liability arising from the operation of the customer’s generating facility.

Although the basic principle is sound-utilities should not be held responsible for property damage or personal injury attributable to someone else-indemnity provisions should not favor the utility but should be fair to both parties.

Look for language that says, “each party shall indemnify the other…” rather than “the customer shall indemnify the utility . . .”

Customer Charges

Customer charges can take a variety of forms, including interconnection charges, metering charges, and standby charges, among others. You should not hesitate to question any charges that seem inappropriate to you.

Federal law (Public Utility Regulatory Policies Act of 1978, or PURPA, Section 210) prohibits utilities from assessing discriminatory charges to customers who have their own generation facilities.

What Do You Need To Know When Connecting Solar Electric System to the Utility Grid

n the past, most homes with solar electric systems were not connected to the local utility grid. It made sense to install solar electric systems in areas without easy assess to the power grid, where the option of extending a power line from the grid might cost tens of thousands of dollars.

In recent years, however, the number of solar-powered homes connected to the local utility grid has increased dramatically. These “grid-connected” buildings have solar electric panels or “modules” that provide some or even most of their power, while still being connected to the local utility. Owners of grid-connected homes can choose to supply a portion of their energy with solar energy, using the utility for power during the night or on cloudy days. Because of the up-front costs of installing a solar electric system, many of these homeowners initially install systems that meet about one quarter to one-half of their energy use.

Solar electric systems sometimes produce more electricity than your home needs. This extra electricity is either stored in batteries or fed into the utility grid. Homeowners can be given credit by their local power companies for the electricity produced at their homes through “net metering” programs.

Net metering

Simple scheme of connecting solar electric system to the grid

Grid-connected systems generally use a billing process called “net metering” or “net billing”. In this process, any energy generated by the solar modules that your home does not use immediately is sent to the utility grid.

However, when the solar electric system is producing less power than is needed, you can draw additional power from the grid. If your system is connected to the grid through a single electric meter, your meter can actually run backwards as you contribute excess energy to the utility.

The excess electricity is being credited to you at the same retail rate as the electricity you use from the utility. Your utility may require the use of two meters—one that meters your consumption of energy from the grid and the other that meters your contribution to the grid. In this case, your solar-generated excess energy could be credited at the retail rate or possibly at a lower wholesale rate, depending on the utility.

In addition, some utilities bill their customers according to a “time-of-use” rate system. Under this system, customers are billed at a higher rate during certain times of the day, such as during the sunniest daytime hours of summer when air conditioners are working at their peak. If this is the case with your utility, you may be able to “trade” your excess energy to the utility at these same rates.

You can therefore benefit from the fact that your solar electric modules produce the most power during those sunny summer days. When you need power from the utility during the off-peak periods, such as in the evening, the rate is usually lower. If you choose to have a grid-connected solar electric system, and your system produces enough energy in any given month so that you do not have to draw from the grid, you may still receive a small monthly bill. This is because many utilities charge monthly fees for meter reading. Again, check with your local utility.

Connecting to the grid

One of the most important steps in purchasing a grid-connected solar electric system is choosing a provider with experience. A good provider will also have a properly licensed electrical contractor, have enough years of experience to have demonstrated an ability to work with customers, and be able to compete effectively with other firms.

A good provider should be familiar with your local utility’s regulations on interconnection requirements. If your provider is not familiar with these requirements, check with your local utility, state energy office, or state or local Public Utility Commission for details.

Your solar electric provider should supply you with everything you need to run your system, including a specific type of inverter for grid-connected systems, batteries (if you want backup power), and a special electric meter. As mentioned already, some utilities require you to have one electric meter that runs both forward and backward. Other utilities require two separate meters: one for incoming power you receive, and one for power you generate that goes back into the system. These meters are sometimes paid for by the utility, but may be part of your provider’s price for the system.

As part of the installation of your solar electric system, you will need to sign an interconnection agreement with the utility company. Your solar electric provider may be able to handle the negotiations and paperwork with the utility, but this contractual agreement is between you and your local utility. Be sure to read the fine print in this agreement, which may differ considerably from one utility to another. It could range from a short one-page statement to a lengthy booklet. In either case, the fine print may contain references to liability issues that you will want to fully understand before signing the contract.

Also, be sure to speak with your homeowner’s insurance provider, because the solar electric system itself will need to be added to your policy. In many cases, you may have to add a rider to your policy for the grid connected system.