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Grid parity

Grid parity is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Grid parity rather than just read about it. In short: Grid parity (or socket parity) occurs when an alternative energy source can generate power at a levelized cost of electricity (LCOE) that is less than or equal to the price of power from the electricity grid. The term is most commonly used when discussing renewable energy sources, notably solar power and wind power.

Grid parity — main illustration
Grid parity — illustration

Key takeaways

  • Grid parity belongs to physics; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Grid parity to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Grid parity from memory before moving on to harder problems.

Reference excerpt

Grid parity (or socket parity) occurs when an alternative energy source can generate power at a levelized cost of electricity (LCOE) that is less than or equal to the price of power from the electricity grid. The term is most commonly used when discussing renewable energy sources, notably solar power and wind power. Grid parity depends upon whether figures are calculated from the point of view of a utility or of a retail consumer. Reaching grid parity is considered to be the point at which an energy source becomes a contender for widespread development without subsidies or government support. It is widely believed that a wholesale shift in generation to these forms of energy will take place when they reach grid parity. Germany was one of the first countries to reach parity for solar PV in 2011 and 2012 for utility-scale solar and rooftop solar PV, respectively. By January 2014, grid parity for solar PV systems had already been reached in at least nineteen countries. Wind power reached grid parity in some places in Europe in the mid 2000s, and has continued to reduce in price.

Overview The price of electricity from the grid is complex. Most power sources in the developed world are generated in industrial scale plants developed by private or public consortia. The company providing the power and the company delivering that power to the customers are often separate entities who enter into a Power Purchase Agreement that sets a fixed rate for all of the power delivered by the plant. On the other end of the wire, the local distribution company (LDC) charges rates that will cover their power purchases from the variety of producers they use. This relationship is not straightforward; for instance, an LDC may buy large amounts of base load power from a nuclear plant at a low fixed cost and then buy peaking power only as required from natural gas peakers at a much higher cost, perhaps five to six times. Depending on their billing policy, this might be billed to the customer at a flat rate combining the two rates the LDC pays, or alternately based on a time-based pricing policy that tries to more closely match input costs with customer prices. As a result of these policies, the exact definition of "grid parity" varies not only from location to location, but customer to customer and even hour to hour. For instance, wind power connects to the grid on the distribution side (as opposed to the customer side). This means it competes with other large forms of industrial-scale power like hydro, nuclear or coal-fired plants, which are generally inexpensive forms of power. Additionally, the generator will be charged by the distribution operator to carry the power to the markets, adding to their levelized costs. Solar has the advantage of scaling easily from systems as small as a single solar panel placed on the customer's roof. In this case the system has to compete with the post-delivery retail price, which is generally much higher than the wholesale price at the same time. It is also important to consider changes in grid pricing when determining whether or not a source is at parity. For instance, the introduction of time-of-use pricing and a general increase in power prices in Mexico during 2010 and 2011 has suddenly resulted in many forms of renewable energy reaching grid parity. A drop in power prices, as has happened in some locations due to the late-2000s recession, can likewise render systems formerly at parity, to be no longer interesting. In general terms, fuel prices continue to increase, while renewable energy sources continue to reduce in up-front costs. As a result, widespread grid parity for wind and solar were generally predicted for the time between 2015 and 2020.

Solar power

Pricing solar

… excerpt ends here. Continue reading the full article.

Illustrations

Grid parity: Grid parity for solar PV systems around the world.mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;margin:1px 0;text-align:center;border:1px solid black;background-color:transparent;color:black}.mw-parser-output .legend-text{}  Reached grid-parity before 2014  Reached grid-parity after 2014  Reached grid-parity only for peak prices  U.S. states poised to reach grid-paritySource: Deutsche Bank, as of February 2015 (see file description)
Grid parity for solar PV systems around the world.mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;margin:1px 0;text-align:center;border:1px solid black;background-color:transparent;color:black}.mw-parser-output .legend-text{}  Reached grid-parity before 2014  Reached grid-parity after 2014  Reached grid-parity only for peak prices  U.S. states poised to reach grid-paritySource: Deutsche Bank, as of February 2015 (see file description)
Grid parity: Projection of levelized cost of electricity for solar PV in Europe[4]
Projection of levelized cost of electricity for solar PV in Europe[4]
Grid parity: Swanson's law–stating that solar module prices have dropped about 20% for each doubling of installed capacity—defines the "learning rate" of solar photovoltaics.[5][6]
Swanson's law–stating that solar module prices have dropped about 20% for each doubling of installed capacity—defines the "learning rate" of solar photovoltaics.[5][6]

Worked examples

Example 1 — a first encounter with Grid parity

Start with the simplest possible case. Write down what Grid parity claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Grid parity before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Grid parity ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Grid parity

In research
Grid parity appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Grid parity in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Grid parity is common in secondary-school and first-year university syllabi. It links to neighbouring topics Renewable electricity, Renewable energy economics, so understanding it makes those chapters shorter.
In everyday life
Look for Grid parity outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Grid parity in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Grid parity means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Grid parity out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Grid parity in simple terms?

Grid parity (or socket parity) occurs when an alternative energy source can generate power at a levelized cost of electricity (LCOE) that is less than or equal to the price of power from the electricity grid. The term is most commonly used when discussing renewable energy sources, notably solar pow…

Why does Grid parity matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Grid parity?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Grid parity.

Tags

  • Renewable electricity
  • Renewable energy economics

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