Power export metering/Net metering

Power export metering
Many electricity customers are installing their own electricity generating equipment, whether for reasons of economy or environmental reasons. When a customer is generating more electricity than required for his own use, the surplus may be exported back to the power grid. Customers that generate back into the "grid" usually must have special equipment and/or safety devices to protect the grid components (as well as the customer's own) in case of faults (electrical short circuits) or maintenance of the grid (say voltage potential on a downed line going into an exporting customers facility).

This exported energy may be accounted for in the simplest case by the meter running backwards during periods of net export, thus reducing the customer's recorded energy usage by the amount exported. This in effect results in the customer being paid for his/her exports at the full retail price of electricity. Unless equipped with a detent or equivalent, a standard meter will accurately record power flow in each direction by simply running backwards when power is exported. Such meters are no longer legal in the UK but instead a meter capable of separately measuring imported and exported energy is required. Where allowed by law, utilities maintain a profitable margin between the price of energy delivered to the consumer and the rate credited for consumer-generated energy that flows back to the grid. Lately, upload sources typically originate from renewable sources (e.g., wind turbines, photovoltaic cells), or gas or steam turbines, which are often found in cogeneration systems. Another potential upload source that has been proposed is plug-in hybrid car batteries (vehicle-to-grid power systems). This requires a "smart grid," which includes meters that measure electricity via communication networks that require remote control and give customers timing and pricing options. Vehicle-to-grid systems could be installed at workplace parking lots and garages and at park and rides and could help drivers charge their batteries at home at night when off-peak power prices are cheaper, and receive bill crediting for selling excess electricity back to the grid during high-demand hours.


Net metering

The examples and perspective in this article deal primarily with North America and do not represent a worldwide view of the subject. Please improve this article and discuss the issue on the talk page.

Net metering is an electricity policy for consumers who own (generally small) renewable energy facilities, such as wind, solar power or home fuel cells. "Net", in this context, is used in the sense of meaning "what remains after deductions" — in this case, the deduction of any energy outflows from metered energy inflows. Under net metering, a system owner receives retail credit for at least a portion of the electricity they generate. Most electricity meters accurately record in both directions, allowing a no-cost method of effectively banking excess electricity production for future credit. However, the rules vary significantly by country and possibly state/province; if net metering is available, if and how long you can keep your banked credits, and how much the credits are worth (retail/wholesale). Most net metering laws involve monthly roll over of kWh credits, a small monthly connection fee, require monthly payment of deficits (i.e. normal electric bill), and annual settlement of any residual credit. Unlike a Feed-in Tariff or time of use metering (TOU), net metering can be implemented solely as an accounting procedure, and requires no special metering, or even any prior arrangement or notification.[1]

Net Metering is generally a consumer-based renewable energy incentive. While it is important to have Net Metering available for any consumer that interconnects their renewable generator to the grid, this form of renewable incentive places the burdens of pioneering renewable energy primarily upon fragmented consumers. Often over-burdened energy agencies are not providing incentives on a consistent basis and it is difficult for individuals to negotiate with large institutions to recover their Net Metering credits and/or rebates for using renewable energy.
In the U.S.A., as part of the Energy Policy Act of 2005, under Sec. 1251, all public electric utilities are now required to make available upon request net metering to their customers.

[2]: ‘‘(11) NET METERING.—Each electric utility shall make available upon request net metering service to any electric consumer that the electric utility serves. For purposes of this paragraph, the term ‘net metering service’ means service to an electric consumer under which electric energy generated by that electric consumer from an eligible on-site generating facility and delivered to the local distribution facilities may be used to offset electric energy provided by the electric utility to the electric consumer during the applicable billing period.

In Canada, some Canadian provinces have net metering programs.
The United Kingdom government is reluctant to introduce the net metering principle because of complications in paying and refunding the value added tax that is payable on electricity, but pilot projects are underway in some areas.

Time of use metering
Further information: Smart meter
Time of use (TOU) net metering employs a specialized reversible smart (electric) meter that is programmed to determine electricity usage any time during the day. Time-of-use allows utility rates and charges to be assessed based on when the electricity was used (ie, day/night and seasonal rates). Typically the production cost of electricity is highest during the daytime peak usage period, and low during the night, when usage is low. Time of use metering is a significant issue for renewable-energy sources, since, for example, solar power systems tend to produce energy during the daytime peak-price period, and produce little or no power during the night period, when price is low.

Market rate net metering
Further information: Vehicle-to-grid
In market rate net metering systems the user's energy use is priced dynamically according to some function of wholesale electric prices. The users' meters are programmed remotely to calculate the value and are read remotely. Net metering applies such variable pricing to excess power produced by a qualifying systems.

Market rate metering systems will be implemented in California starting in 2006 and under the terms of California's net metering rules will be applicable to qualifying photovoltaic and wind systems. Under California law the payback for surplus electricity sent to the grid must be equal to the (variable, in this case) price charged at that time. It can never be negative, meaning you cannot make money from selling the electricity back. If you generate more electricity than you use then over a period of a month you will be billed zero and not make any money, in effect you give away your extra energy if you do not use it.

Net metering enables small systems to result in zero annual net cost to the consumer provided that the consumer is able to shift demand loads to a lower price time, such as by chilling water at a low cost time for later use in air conditioning, or by charging a battery electric vehicle during off-peak times, while the electricity generated at peak demand time can be sent to the grid rather than used locally (see Vehicle-to-grid). No credit is given for annual surplus production.

Australia
Main article: Feed-in tariffs in Australia
Australia's "feed-in tariff" is actually net metering, except that it pays monthly for net generation at a higher rate than retail, with Environment Victoria Campaigns Director Mark Wakeham calling it a "fake feed-in tariff".[3] A feed-in tariff requires a separate meter, and pays for all local generation at a preferential rate, while net metering requires only one meter. The financial differences are very substantial.

Victoria
From 2009, householders will be paid 60 cents for every excess kilowatt hour of energy fed back into the state electricity grid. This is around four times the current retail price for electricity.

Queensland
Commencing in 2008, the Solar Bonus Scheme pays 44 cents for every excess kilowatt hour of energy fed back into the state electricity grid. This is around three times the current retail price for electricity.

Canada
Ontario

Ontario allows net metering for up to 500 kW, however credits can only be carried for 12 consecutive months. Should a consumer establish a credit where they generate more than they consume for 8 months and use up the credits in the 10th month then the 12 month period begins again from the date that the next credit is shown on an invoice. Any unused credits remaining at the end of 12 consecutive months of a consumer being in a credit situation are cleared at the end of that billing.[4]

British Columbia
Areas of British Columbia serviced by BC Hydro are allowed net metering for up to 50 kW. At each annual anniversary the customer is paid 8.16 cents / kWh if there is a net export of power. Systems over 50 kW are covered under the Standard Offer Program.[5] FortisBC which serves an area in South Central BC is currently studying the implementation of net-metering.[6] The City of New Westminster which has its own electrical utility does not currently allow net-metering.

United States
Several bills are pending that require utilities to provide net metering. They range from H.R. 729 which allows up to 2% net metering to H.R. 1945 which has no limit, but does limit residential users to 10 kW, a low limit compared to New Jersey and Colorado's 2 MW limit, the two states with laws most favorable to consumers in 2007.[7] By March, 2009 only six states did not allow net metering, and seventeen plus Washington D.C. have no limit on the number of subscribers using net metering. Only two, Arizona and Ohio, have no limit on the power limit for each subscriber (see table).

California
Consumer Net Metering is available in California and is presumed to be highly favorable to smaller systems that displace the highest cost electricity, and systems wherein the user's demand load may be managed so that there is a net production of electricity during high cost periods. This can be done, for example, by chilling water during off-peak times for air conditioning use during high demand periods, or by pre-cooling the thermal mass of the building during low cost periods.
A hiccup has occurred in California legislation (SB1 - 2006), in that new (after Jan. 1, 2007) residential solar systems are singled out to be billed on TOU schedules, and at least one utility (Southern California Edison (SCE)) has rate structures which are punitive to the solar customer, particularly for smaller systems that cannot keep up with peak demands. This faulty legislation created a disincentive to new solar installations, and/or windfall profits to SCE. This has since been remedied through legislation.

Colorado
No limit on enrollment, system size is limited to 2 MW, excess is credited to customer's next bill; utility pays customer at end of calendar year for excess kWh credits at the average hourly incremental cost for that year.[8]

Florida
Passed by Florida Public Service Commission 4 March 2008, system size is limited to 2 MW, with compensation up to the account's electrical consumption as trued up at end of calendar year. Excess production is not compensated.

Kansas
Kansas does not have a consumer Net Metering incentive, but does have a renewable metering incentive on the wholesale level that provides the wholesale commerce of renewable energy at 150% of the avoided cost. Thus, the incentive one receives in this case is dependent not upon the price ofelectricity per kWh, but upon the price of wholesale electricity.
The Kansas Solar Electric Co~operatives [K-SEC] was founded January 2005 by Eileen M. Smith, M.Arch. VITAE as a non-profit and non-competitive renewable electricity cooperative. K-SEC Phase I Demonstration is structured around Kansas House Bill 2018 passed in 2003 by Kansas Representative Tom Sloan. See Kansas Statutes Annotated Chapter 17-4661 and 17-4655

The K-SEC program has the goal of installing 1,000 MWp building-integrated photo voltaic [BI-PV] solar electricity by 2018. This translates to approximately 100,000,000 sq ft (9,300,000 m2) of BI-PV solar roofing or one million sqft BI-PV roofing in 100 of the 105 counties of Kansas. This will require 70,000 to 100,000 sq ft (9,300 m2) BI-PV per county per year for ten years. K-SEC will not sell the solar systems, but they are going to lease consumer rooftops in exchange for a high-tech battery back-up system for fifty years. K-SEC will manufacture, install, monitor, maintain and sell the electricity wholesale. K-SEC will provide numerous job opportunities to rural and urban Kansas communities from manufacturing to solar system design, installation, maintenance, monitoring and electricity sells.

The foundational structure for the K-SEC Program is the Kansas Solar Electric Buildings Registry and GIS Database. A list is being compiled of Kansas homes and buildings that have unshaded roofing surface that could accommodate 100 sq ft (9.3 m2) to 50,000 sq ft (4,600 m2) of BI-PV solar materials. The rooftops must have south to southwest facing or flat rooftops.

The K-SEC Program is important for Kansas where 72.5% of the electricity Kansas presently consumes is generated by coal-fired power plants. In 2004 and 2005 projects totaling a 55% increase in coal-fired power plants were proposed in Kansas.

New Jersey
No limit on enrollment, system size is limited to 2 MW, excess is credited to customer's next bill at retail rate; purchased by utility at avoided-cost rate at end of 12-month billing cycle.[10]

North Carolina
In North Carolina initial net metering rules were put in place in 2005 to prohibit systems that include backup battery power, but due to consumer feedback the restriction was lifted in July 2006.

Texas
Residential
In Texas' deregulated electricity market, credit for electricity exported to the grid is awarded at the discretion of the Retail Electric Provider (REP), the company responsible for the retail sale of electricity to end-use customers.[11] Green Mountain Energy offers to purchase up to 500kwh per month at full retail rate with additional outflow compensated at 50%.[12] Austin Energy buys back exported energy at the "current fuel charge" and participants in the GreenChoice program are compensated at the Green Power rate of charge.
Commercial

The limit on system size is 100 kW for qualifying facilities; 50 kW for renewables. The treatment of net excess is purchased by utility for a given billing period at avoided-cost rate. It applies only to all integrated IOUs (Investor Owned Utilities) that have not unbundled in accordance with Public Utility Regulatory Act § 39.05; does not apply to municipal utilities, river authorities and electric cooperatives [14].

Net purchase and sale
Net purchase and sale is a different method of providing power to the electricity grid that does not offer the price symmetry of net metering, making this system a lot less profitable for home users of small renewable energy systems.

Under this arrangement, two uni-directional meters are installed—one records electricity drawn from the grid, and the other records excess electricity generated and fed back into the grid. The user pays retail rate for the electricity they use, and the power provider purchases their excess generation at its avoided cost (wholesale rate). There may be a significant difference between the retail rate the user pays and the power provider's avoided cost.[]

Germany and Spain, on the other hand, have adopted a price schedule, or Feed-in Tariff (FIT), whereby customers get paid for any electricity they generate from renewable energy on their premises. The actual electricity being generated is counted on a separate meter, not just the surplus they feed back to the grid. In Germany, for the solar power generated, a feed-in tariff of somewhat more than 2 times the retail rate per kWh for residential customers is being paid in order to boost solar power (figure from 2009). Wind energy, in contrast, only receives around a half of the domestic retail rate, because the German system pays what each source costs (including a reasonable profit margin).

Related technology
Sources that produce direct current, such as solar panels must be coupled with an electrical inverter to convert the output to alternating current, for use with conventional appliances. The phase of the outgoing power must be synchronized with the grid, and a mechanism must be included to disconnect the feed in the event of grid failure. This is for safety - for example, workers repairing downed power lines must be protected from "downstream" sources, in addition to being disconnected from the main "upstream" distribution grid.