Cost of electricity

The distinct ways of electricity generation can incur significantly different costs. Calculations of these costs can be made at the point of connection to a load or to the electricity grid. The cost is typically given per kilowatt-hour or megawatt-hour. It includes the initial capital, discount rate, as well as the costs of continuous operation, fuel, and maintenance. This type of calculation assists policymakers, researchers and others to guide discussions and decision making.

The **levelized cost of energy** (**LCOE**) is a measure of a power source that allows comparison of different methods of electricity generation on a consistent basis. It is an economic assessment of the average total cost to build and operate a power-generating asset over its lifetime divided by the total energy output of the asset over that lifetime. The LCOE can also be regarded as the average minimum price at which electricity must be sold in order to break-even over the lifetime of the project.

## Cost factors

While calculating costs, several internal cost factors have to be considered. Note the use of "costs," which is not the actual selling price, since this can be affected by a variety of factors such as subsidies and taxes:

* Capital costs (including waste disposal and decommissioning costs for nuclear energy) – tend to be low for gas and oil power stations; moderate for onshore wind turbines and solar PV (photovoltaics); higher for coal plants and higher still for waste to energy, wave and tidal, solar thermal, offshore wind and nuclear.
* Fuel costs – high for fossil fuel and biomass sources, low for nuclear, and zero for many renewables. Fuel costs can vary somewhat unpredictably over the life of the generating equipment, due to political and other factors.
* Factors such as the costs of waste (and associated issues) and different insurance costs are not included in the following: Works power, own use or parasitic load – that is, the portion of generated power actually used to run the station's pumps and fans has to be allowed for.

To evaluate the total cost of production of electricity, the streams of costs are converted to a net present value using the time value of money. These costs are all brought together using discounted cash flow.

### Capital costs

For power generation capacity capital costs are often expressed as overnight cost per watt. Estimated costs are:

* gas/oil combined cycle power plant - $1000/kW
* onshore wind - $1600/kW
* offshore wind - $6500/kW
* solar PV (fixed) - $1060/kW (utility), $1800/kW
* solar PV (tracking)- $1130/kW (utility) $2000/kW
* battery storage power - $2000/kW
* conventional hydropower - $2680/kW
* geothermal - $2800/kW
* coal (with SO2 and NOx controls)- $3500–3800/kW
* advanced nuclear - $6000/kW
* fuel cells - $7200/kW

### Running costs

Running costs include the cost of any fuel, maintenance costs, repair costs, wages, handling any wastes etc.

Fuel costs can be given per kWh and tend to be highest for oil fired generation, with coal being second and gas being cheaper. Nuclear fuel is very cheap per kWh.

### Levelized cost of electricity

The levelized cost of electricity (LCOE), also known as Levelized Energy Cost (LEC), is the net present value of the unit-cost of electrical energy over the lifetime of a generating asset. It is often taken as a proxy for the average price that the generating asset must receive in a market to break even over its lifetime. It is a first-order economic assessment of the cost competitiveness of an electricity-generating system that incorporates all costs over its lifetime: initial investment, operations and maintenance, cost of fuel, cost of capital.

The levelized cost is that value for which an equal-valued fixed revenue delivered over the life of the asset's generating profile would cause the project to break even. This can be roughly calculated as the net present value of all costs over the lifetime of the asset divided by the total electrical energy output of the asset.

The levelized cost of electricity (LCOE) is given by:

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sum of costs over lifetime
sum of electrical energy produced over lifetime

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{\displaystyle
\mathrm{LCOE} = \frac{\text{sum of costs over lifetime}}{\text{sum of electrical energy produced over lifetime}} = \frac{\sum\_{t=1}^{n} \frac{ I\_t + M\_t + F\_t}{\left({1+r}\right)^t} }{\sum\_{t=1}^{n} \frac{E\_t}{\left({1+r}\right)^{t}} }
}

Note: Some caution must be taken when using formulas for the levelized cost, as they often embody unseen assumptions, neglect effects like taxes, and may be specified in real or nominal levelized cost. For example, other versions of the above formula do not discount the electricity stream.
Typically the LCOE is calculated over the design lifetime of a plant, which is usually 20 to 40 years, and given in the units of currency per kilowatt-hour or megawatt-day, for example AUD/kWh or EUR/kWh or per megawatt-hour, for example AUD/MWh (as tabulated below). However, care should be taken in comparing different LCOE studies and the sources of the information as the LCOE for a given energy source is highly dependent on the assumptions, financing terms and technological deployment analyzed. In particular, assumption of capacity factor has significant impact on the calculation of LCOE. Thus, a key requirement for the analysis is a clear statement of the applicability of the analysis based on justified assumptions.

Many scholars, such as Paul Joskow, have described limits to the "levelized cost of electricity" metric for comparing new generating sources. In particular, LCOE ignores time effects associated with matching production to demand. This happens at two levels:

* Dispatchability, the ability of a generating system to come online, go offline, or ramp up or down, quickly as demand swings.
* The extent to which the availability profile matches or conflicts with the market demand profile.

Thermally lethargic technologies like coal and solid-fuel nuclear are physically incapable of fast ramping. However, many designs of Generation 4 molten fuel nuclear reactors will be capable of fast ramping because (A) the neutron poison xenon-135 can be removed from the reactor while it runs leaving no need to compensate for xenon-135 concentrations and (B) the large negative thermal and void coefficients of reactivity automatically reduce or increase fission output as the molten fuel heats or cools, respectively.
Nevertheless, capital intensive technologies such as wind, solar, and nuclear are economically disadvantaged unless generating at maximum availability since the LCOE is nearly all sunk-cost capital investment. Intermittent power sources, such as wind and solar, may incur extra costs associated with needing to have storage or backup generation available. At the same time, intermittent sources can be competitive if they are available to produce when demand and prices are highest, such as solar during summertime mid-day peaks seen in hot countries where air conditioning is a major consumer. Despite these time limitations, leveling costs is often a necessary prerequisite for making comparisons on an equal footing before demand profiles are considered, and the levelized-cost metric is widely used for comparing technologies at the margin, where grid implications of new generation can be neglected.

Another limitation of the LCOE metric is the influence of energy efficiency and conservation (EEC).
EEC has caused the electricity demand of many countries to remain flat or decline. Considering only the LCOE for utility scale plants will tend to maximise generation and risks overestimating required generation due to efficiency, thus "lowballing" their LCOE. For solar systems installed at the point of end use, it is more economical to invest in EEC first, then solar (resulting in a smaller required solar system than what would be needed without the EEC measures). However, designing a solar system on the basis of LCOE would cause the smaller system LCOE to increase (as the energy generation [measured in kWh] drops faster than the system cost [$]). The whole of system life cycle cost should be considered, not just the LCOE of the energy source. LCOE is not as relevant to end-users than other financial considerations such as income, cashflow, mortgage, leases, rent, and electricity bills. Comparing solar investments in relation to these can make it easier for end-users to make a decision, or using cost-benefit calculations "and/or an asset’s capacity value or contribution to peak on a system or circuit level".

### Avoided cost

The US Energy Information Administration has recommended that levelized costs of non-dispatchable sources such as wind or solar may be better compared to the avoided energy cost rather than to the LCOE of dispatchable sources such as fossil fuels or geothermal. This is because introduction of fluctuating power sources may or may not avoid capital and maintenance costs of backup dispatchable sources. Levelized Avoided Cost of Energy (LACE) is the avoided costs from other sources divided by the annual yearly output of the non-dispatchable source. However, the avoided cost is much harder to calculate accurately.

### Marginal cost of electricity

A more accurate economic assessment might be the marginal cost of electricity. This value works by comparing the added system cost of increasing electricity generation from one source versus that from other sources of electricity generation (see Merit Order).

### External costs of energy sources

See also: Environmental impact of the energy industry, Economics of new nuclear power plants
Typically pricing of electricity from various energy sources may not include all external costs – that is, the costs indirectly borne by society as a whole as a consequence of using that energy source. These may include enabling costs, environmental impacts, usage lifespans, energy storage, recycling costs, or beyond-insurance accident effects.

The US Energy Information Administration predicts that coal and gas are set to be continually used to deliver the majority of the world's electricity. This is expected to result in the evacuation of millions of homes in low-lying areas, and an annual cost of hundreds of billions of dollars' worth of property damage.

Furthermore, with a number of island nations becoming slowly submerged underwater due to rising sea levels, massive international climate litigation lawsuits against fossil fuel users are currently beginning in the International Court of Justice.

An EU funded research study known as ExternE, or Externalities of Energy, undertaken over the period of 1995 to 2005 found that the cost of producing electricity from coal or oil would double over its present value, and the cost of electricity production from gas would increase by 30% if external costs such as damage to the environment and to human health, from the particulate matter, nitrogen oxides, chromium VI, river water alkalinity, mercury poisoning and arsenic emissions produced by these sources, were taken into account. It was estimated in the study that these external, downstream, fossil fuel costs amount up to 1%–2% of the EU’s entire Gross Domestic Product (GDP), and this was before the external cost of global warming from these sources was even included. Coal has the highest external cost in the EU, and global warming is the largest part of that cost.

A means to address a part of the external costs of fossil fuel generation is carbon pricing — the method most favored by economics for reducing global-warming emissions. Carbon pricing charges those who emit carbon dioxide (CO2) for their emissions. That charge, called a 'carbon price', is the amount that must be paid for the right to emit one tonne of CO2 into the atmosphere. Carbon pricing usually takes the form of a carbon tax or a requirement to purchase permits to emit (also called "allowances").

Depending on the assumptions of possible accidents and their probabilites external costs for nuclear power vary significantly and can reach between 0.2 and 200 ct/kWh. Furthermore, nuclear power is working under an insurance framework that limits or structures accident liabilities in accordance with the Paris convention on nuclear third-party liability, the Brussels supplementary convention, and the Vienna convention on civil liability for nuclear damage and in the U.S. the Price-Anderson Act. It is often argued that this potential shortfall in liability represents an external cost not included in the cost of nuclear electricity; but the cost is small, amounting to about 0.1% of the levelized cost of electricity, according to a CBO study.

These beyond-insurance costs for worst-case scenarios are not unique to nuclear power, as hydroelectric power plants are similarly not fully insured against a catastrophic event such as the Banqiao Dam disaster, where 11 million people lost their homes and from 30,000 to 200,000 people died, or large dam failures in general. As private insurers base dam insurance premiums on limited scenarios, major disaster insurance in this sector is likewise provided by the state.

Because externalities are diffuse in their effect, external costs can not be measured directly, but must be estimated. One approach estimate external costs of environmental impact of electricity is the Methodological Convention of Federal Environment Agency of Germany. That method arrives at external costs of electricity from lignite at 10.75 Eurocent/kWh, from hard coal 8.94 Eurocent/kWh, from natural gas 4.91 Eurocent/kWh, from photovoltaic 1.18 Eurocent/kWh, from wind 0.26 Eurocent/kWh and from hydro 0.18 Eurocent/kWh. For nuclear the Federal Environment Agency indicates no value, as different studies have results that vary by a factor of 1,000. It recommends the nuclear given the huge uncertainty, with the cost of the next inferior energy source to evaluate. Based on this recommendation the Federal Environment Agency, and with their own method, the Forum Ecological-social market economy, arrive at external environmental costs of nuclear energy at 10.7 to 34 ct/kWh.

### Additional cost factors

Calculations often do not include wider system costs associated with each type of plant, such as long distance transmission connections to grids, or balancing and reserve costs. Calculations do not include externalities such as health damage by coal plants, nor the effect of CO2 emissions on the climate change, ocean acidification and eutrophication, ocean current shifts. Decommissioning costs of power plants are usually not included (nuclear power plants in the United States is an exception, because the cost of decommissioning is included in the price of electricity per the Nuclear Waste Policy Act), is therefore not full cost accounting. These types of items can be explicitly added as necessary depending on the purpose of the calculation. It has little relation to actual price of power, but assists policy makers and others to guide discussions and decision making.

These are not minor factors but very significantly affect all responsible power decisions:

* Comparisons of life-cycle greenhouse gas emissions show coal, for instance, to be radically higher in terms of GHGs than any alternative. *Accordingly, in the analysis below, carbon captured coal is generally treated as a separate source rather than being averaged in with other coal.*
* Other environmental concerns with electricity generation include acid rain, ocean acidification and effect of coal extraction on watersheds.
* Various human health concerns with electricity generation, including asthma and smog, now dominate decisions in developed nations that incur health care costs publicly. A Harvard University Medical School study estimates the US health costs of coal alone at between 300 and 500 billion US dollars annually.
* While cost per kWh of transmission varies drastically with distance, the long complex projects required to clear or even upgrade transmission routes make even attractive new supplies often uncompetitive with conservation measures (see below), because the timing of payoff must take the transmission upgrade into account.

## Current global studies

### Lazard (2018)

In November, 2018, Lazard found that not only are utility-scale solar and wind cheaper than fossil fuels, "[i]n some scenarios, alternative energy costs have decreased to the point that they are now at or below the marginal cost of conventional generation."
Overall, Lazard found "The low end levelized cost of onshore wind-generated energy is $29/MWh, compared to an average illustrative marginal cost of $36/MWh for coal. The levelized cost of utility-scale solar is nearly identical to the illustrative marginal cost of coal, at $36/MWh. This comparison is accentuated when subsidizing onshore wind and solar, which results in levelized costs of energy of $14/MWh and $32/MWh, respectively. ... The mean levelized cost of energy of utility-scale PV technologies is down approximately 13% from last year and the mean levelized cost of energy of onshore wind has declined almost 7%."

### Bloomberg (2018)

Bloomberg New Energy Finance estimates a "global LCOE for onshore wind [of] $55 per megawatt-hour, down 18% from the first six months of [2017], while the equivalent for solar PV without tracking systems is $70 per MWh, also down 18%." Bloomberg does not provide its global public LCOEs for fossil fuels, but it notes in India they are significantly more expensive: "BNEF is now showing benchmark LCOEs for onshore wind of just $39 per MWh, down 46% on a year ago, and for solar PV at $41, down 45%. By comparison, coal comes in at $68 per MWh, and combined-cycle gas at $93."

### IRENA (2018)

The International Renewable Energy Agency (IRENA) released a study based on comprehensive international datasets in January 2018 which projects the fall by 2020 of the kilowatt cost of electricity from utility scale renewable projects such as onshore wind farms to a point equal or below that of electricity from conventional sources.

### Banks (2018)

The European Bank for Reconstruction and Development (EBRD) says that "renewables are now cheapest energy source", elaborating: "the Bank believes that renewable energy markets in many of the countries where it invests have reached a stage where the introduction of competitive auctions will lead both to a steep drop in electricity prices and an increase in investment." The World Bank (World Bank) President Jim Yong Kim agreed on 10 October 2018: "We are required by our by-laws to go with the lowest cost option, and renewables have now come below the cost of [fossil fuels]."

## Regional and historical studies

### Australia

LCOE in AUD per MWh for some coal and wind technologies (2012) from the Australian Technology Assessment (2012), Table 5.2.1.
 Wind | $111 – $122 | $111 – $122

According to various studies, the cost for wind and solar has dramatically reduced since 2006. For example, the Australian Climate Council states that over the 5 years between 2009–2014 solar costs fell by 75% making them comparable to coal, and are expected to continue dropping over the next 5 years by another 45% from 2014 prices. They also found that wind has been cheaper than coal since 2013, and that coal and gas will become less viable as subsidies are withdrawn and there is the expectation that they will eventually have to pay the costs of pollution.

A CO2CRC report, printed on the 27th of November 2015, titled "Wind, solar, coal and gas to reach similar costs by 2030:", provides the following updated situation in Australia. "The updated LCOE analysis finds that in 2015 natural gas combined cycle and supercritical pulverised coal (both black and brown) plants have the lowest LCOEs of the technologies covered in the study. Wind is the lowest cost large-scale renewable energy source, while rooftop solar panels are competitive with retail electricity prices. By 2030 the LCOE ranges of both conventional coal and gas technologies as well as wind and large-scale solar converge to a common range of A$50 to A$100 per megawatt hour."

An updated report, posted on the 27th of September 2017, titled "Renewables will be cheaper than coal in the future. Here are the numbers", indicated that a 100% renewables system is competitive with new-build supercritical (ultrasupercritical) coal, which, according to the Jacobs calculations in the report link above, would come in at around A$75(80) per MWh between 2020 and 2050. This projection for supercritical coal is consistent with other studies by the CO2CRC in 2015 (A$80 per MWh) and used by CSIRO in 2017 (A$65–80 per MWh).

### France

The International Energy Agency and EDF have estimated for 2011 the following costs. For nuclear power, they include the costs due to new safety investments to upgrade the French nuclear plant after the Fukushima Daiichi nuclear disaster; the cost for those investments is estimated at 4 €/MWh. Concerning solar power, the estimate of 293 €/MWh is for a large plant capable of producing in the range of 50–100 GWh/year located in a favorable location (such as in Southern Europe). For a small household plant that can produce around 3 MWh/year, the cost is between 400 and 700 €/MWh, depending on location. Solar power was by far the most expensive renewable source of electricity among the technologies studied, although increasing efficiency and longer lifespan of photovoltaic panels together with reduced production costs have made this source of energy more competitive since 2011. By 2017, the cost of photovoltaic solar power had decreased to less than 50 €/MWh.

French LCOE in €/MWh (2011)
 Nuclear EPR
 Solar farms | 293 | 43.24

### Germany

In November 2013, the Fraunhofer Institute for Solar Energy Systems ISE assessed the levelised generation costs for newly built power plants in the German electricity sector. PV systems reached LCOE between 0.078 and 0.142 Euro/kWh in the third quarter of 2013, depending on the type of power plant (ground-mounted utility-scale or small rooftop solar PV) and average German insolation of 1000 to 1200 kWh/m² per year (GHI). There are no LCOE-figures available for electricity generated by recently built German nuclear power plants as none have been constructed since the late 1980s. An update of the ISE study was published in March 2018.

### Japan

A 2010 study by the Japanese government (pre-Fukushima disaster), called the Energy White Paper, concluded the cost for kilowatt hour was ¥49 for solar, ¥10 to ¥14 for wind, and ¥5 or ¥6 for nuclear power.

Masayoshi Son, an advocate for renewable energy, however, has pointed out that the government estimates for nuclear power did not include the costs for reprocessing the fuel or disaster insurance liability. Son estimated that if these costs were included, the cost of nuclear power was about the same as wind power.

### United Kingdom

The Institution of Engineers and Shipbuilders in Scotland commissioned a former Director of Operations of the British National Grid, Colin Gibson, to produce a report on generation levelised costs that for the first time would include some of the transmission costs as well as the generation costs. This was published in December 2011. The institution seeks to encourage debate of the issue, and has taken the unusual step among compilers of such studies of publishing a spreadsheet.

On 27 February 2015 Vattenfall Vindkraft AS agreed to build the Horns Rev 3 offshore wind farm at a price of 10.31 Eurocent per kWh. This has been quoted as below £100 per MWh.

In 2013 in the United Kingdom for a new-to-build nuclear power plant (Hinkley Point C: completion 2023), a feed-in tariff of £92.50/MWh (around 142 USD/MWh) plus compensation for inflation with a running time of 35 years was agreed.

The Department for Business, Energy and Industrial Strategy (BEIS) publishes regular estimates of the costs of different electricity generation sources, following on the estimates of the merged Department of Energy and Climate Change (DECC). Levelized cost estimates for new generation projects begun in 2015 are listed in the table below.

### United States

#### Energy Information Administration

The following data are from the Energy Information Administration's (EIA) Annual Energy Outlook released in 2015 (AEO2015). They are in dollars per megawatt-hour (2013 USD/MWh). These figures are estimates for plants going into service in 2020. The LCOE below is calculated based off a 30-year recovery period using a real after tax weighted average cost of capital (WACC) of 6.1%. For carbon intensive technologies 3 percentage points are added to the WACC. (This is approximately equivalent fee of $15 per metric ton of carbon dioxide CO2)

Since 2010, the US Energy Information Administration (EIA) has published the Annual Energy Outlook (AEO), with yearly LCOE-projections for future utility-scale facilities to be commissioned in about five years' time. In 2015, EIA has been criticized by the Advanced Energy Economy (AEE) Institute after its release of the AEO 2015-report to "consistently underestimate the growth rate of renewable energy, leading to 'misperceptions' about the performance of these resources in the marketplace". AEE points out that the average power purchase agreement (PPA) for wind power was already at $24/MWh in 2013. Likewise, PPA for utility-scale solar PV are seen at current levels of $50–$75/MWh. These figures contrast strongly with EIA's estimated LCOE of $125/MWh (or $114/MWh including subsidies) for solar PV in 2020.

The electricity sources which had the most decrease in estimated costs over the period 2010 to 2019 were solar photovoltaic (down 88%), onshore wind (down 71%) and advanced natural gas combined cycle (down 49%).

For utility-scale generation put into service in 2040, the EIA estimated in 2015 that there would be further reductions in the constant-dollar cost of concentrated solar power (CSP) (down 18%), solar photovoltaic (down 15%), offshore wind (down 11%), and advanced nuclear (down 7%). The cost of onshore wind was expected to rise slightly (up 2%) by 2040, while natural gas combined cycle electricity was expected to increase 9% to 10% over the period.

#### NREL OpenEI (2015)

OpenEI, sponsored jointly by the US DOE and the National Renewable Energy Laboratory (NREL), has compiled a historical cost-of-generation database covering a wide variety of generation sources. Because the data is open source it may be subject to frequent revision.

Note:

Only Median value = only one data point.

Only Max + Min value = Only two data points

#### California Energy Commission (2014)

LCOE data from the California Energy Commission report titled "Estimated Cost of New Renewable and Fossil Generation in California". The model data was calculated for all three classes of developers: merchant, investor-owned utility (IOU), and publicly owned utility (POU).

#### Lazard (2015)

In November 2015, the investment bank Lazard headquartered in New York, published its ninth annual study on the current electricity production costs of photovoltaics in the US compared to conventional power generators. The best large-scale photovoltaic power plants can produce electricity at 50 USD per MWh. The upper limit at 60 USD per MWh. In comparison, coal-fired plants are between 65 USD and $150 per MWh, nuclear power at 97 USD per MWh. Small photovoltaic power plants on roofs of houses are still at 184–300 USD per MWh, but which can do without electricity transport costs. Onshore wind turbines are 32–77 USD per MWh. One drawback is the intermittency of solar and wind power. The study suggests a solution in batteries as a storage, but these are still expensive so far.

Lazard's long standing Levelized Cost of Energy (LCOE) report is widely considered and industry benchmark. In 2015 Lazard published its inaugural Levelized Cost of Storage (LCOS) report, which was developed by the investment bank Lazard in collaboration with the energy consulting firm, Enovation.

Below is the complete list of LCOEs by source from the investment bank Lazard.

NOTE: \*\* Battery Storage is no longer include in this report (2015). It has been rolled into its own separate report LCOS 1.0, developed in consultation with Enovation Partners (See charts below).

Below are the LCOSs for different battery technologies. This category has traditionally been filled by Diesel Engines. These are "Behind the meter" applications.

Below are the LCOSs for different battery technologies. This category has traditionally been filled by Natural Gas Engines. These are "In front of the meter" applications.

#### Lazard (2016)

On December 15, 2016 Lazard released version 10 of their LCOE report and version 2 of their LCOS report.

#### Lazard (2017)

On November 2, 2017 the investment bank Lazard released version 11 of their LCOE report and version 3 of their LCOS report.

Below are the unsubsidized LCOSs for different battery technologies for "Behind the Meter" (BTM) applications.

Below are the Unsubsidized LCOSs for different battery technologies "Front of the Meter" (FTM) applications.

Note: Flow battery value range estimates

### Global

#### IEA and NEA (2015)

The International Energy Agency and the Nuclear Energy Agency published a joint study in 2015 on LCOE data internationally.

### Other studies and analysis

#### Buffett Contract (2015)

In a power purchase agreement in the United States in July 2015 for a period of 20 years of solar power will be paid 3.87 UScent per kilowatt hour (38.7 USD/MWh). The solar system, which produces this solar power, is in Nevada (USA) and has 100 MW capacity.

#### Sheikh Mohammed Bin Rashid solar farm (2016)

In the spring of 2016 a winning bid of 2.99 US cents per kilowatt-hour of photovoltaic solar energy was achieved for the next (800 MW capacity) phase of the Sheikh Mohammed Bin Rashid solar farm in Dubai.

#### Brookings Institution (2014)

In 2014, the Brookings Institution published *The Net Benefits of Low and No-Carbon Electricity Technologies* which states, after performing an energy and emissions cost analysis, that "The net benefits of new nuclear, hydro, and natural gas combined cycle plants far outweigh the net benefits of new wind or solar plants", with the most cost effective low carbon power technology being determined to be nuclear power.

#### Brazilian electricity mix

As long as exergy stands for the useful energy required for an economic activity to be accomplished, it is reasonable to evaluate the cost of the energy on the basis of its exergy content. Besides, as exergy can be considered as measure of the departure of the environmental conditions, it also serves as an indicator of environmental impact, taking into account both the efficiency of supply chain (from primary exergy inputs) and the efficiency of the production processes. In this way, exergoeconomy can be used to rationally distribute the exergy costs and CO2 emission cost among the products and by-products of a highly integrated Brazilian electricity mix. Based on the thermoeconomy methodologies, some authors have shown that exergoeconomy provides an opportunity to quantify the renewable and non-renewable specific exergy consumption; to properly allocate the associated CO2 emissions among the streams of a given production route; as well as to determine the overall exergy conversion efficiency of the production processes. Accordingly, the non-renewable unit exergy cost (cNR) [kJ/kJ] is defined as the rate of non-renewable exergy necessary to produce one unit of exergy rate/flow rate of a substance, fuel, electricity, work or heat flow, whereas the Total Unit Exergy Cost (cT) includes the Renewable (cR) and Non-Renewable Unit Exergy Costs. Analogously, the CO2 emission cost (cCO2) [gCO2/kJ] is defined as the rate of CO2 emitted to obtain one unit of exergy rate/flow rate.

## Renewables

### Photovoltaics

Photovoltaic prices have fallen from $76.67 per watt in 1977 to nearly $0.13 per watt in May 2019, for crystalline silicon solar cells and module price to $0.23 per watt. This is seen as evidence supporting Swanson's law, which states that solar cell prices fall 20% for every doubling of cumulative shipments. The famous Moore's law calls for a doubling of transistor count every two years.

By 2011, the price of PV modules per MW had fallen by 60% since 2008, according to Bloomberg New Energy Finance estimates, putting solar power for the first time on a competitive footing with the retail price of electricity in some sunny countries; an alternative and consistent price decline figure of 75% from 2007 to 2012 has also been published, though it is unclear whether these figures are specific to the United States or generally global. The levelised cost of electricity (LCOE) from PV is competitive with conventional electricity sources in an expanding list of geographic regions, particularly when the time of generation is included, as electricity is worth more during the day than at night. There has been fierce competition in the supply chain, and further improvements in the levelised cost of energy for solar lie ahead, posing a growing threat to the dominance of fossil fuel generation sources in the next few years. As time progresses, renewable energy technologies generally get cheaper, while fossil fuels generally get more expensive:

> The less solar power costs, the more favorably it compares to conventional power, and the more attractive it becomes to utilities and energy users around the globe. Utility-scale solar power [could in 2011] be delivered in California at prices well below $100/MWh ($0.10/kWh) less than most other peak generators, even those running on low-cost natural gas. Lower solar module costs also stimulate demand from consumer markets where the cost of solar compares very favourably to retail electric rates.
>
>
>

In the year 2015, First Solar agreed to supply solar power at 3.87 cents/kWh levelised price from its 100 MW Playa Solar 2 project which is far cheaper than the electricity sale price from conventional electricity generation plants. From January 2015 through May 2016, records have continued to fall quickly, and solar electricity prices, which have reached levels below 3 cents/kWh, continue to fall. In August 2016, Chile announced a new record low contract price to provide solar power for $29.10 per megawatt-hour (MWh). In September 2016, Abu Dhabi announced a new record breaking bid price, promising to provide solar power for $24.2 per MWh In October 2017, Saudi Arabia announced a further low contract price to provide solar power for $17.90 per MWh.

With a carbon price of $50/ton (which would raise the price of coal-fired power by 5c/kWh), solar PV is cost-competitive in most locations. The declining price of PV has been reflected in rapidly growing installations, totaling a worldwide cumulative capacity of 297 GW by end 2016. According to some estimates total investment in renewables for 2011 exceeded investment in carbon-based electricity generation.

In the case of self consumption, payback time is calculated based on how much electricity is not brought from the grid. Additionally, using PV solar power to charge DC batteries, as used in Plug-in Hybrid Electric Vehicles and Electric Vehicles, leads to greater efficiencies, but higher costs. Traditionally, DC generated electricity from solar PV must be converted to AC for buildings, at an average 10% loss during the conversion. Inverter technology is rapidly improving and current equipment has reached 99% efficiency for small scale residential, while commercial scale three-phase equipment can reach well above 98% efficiency. However, an additional efficiency loss occurs in the transition back to DC for battery driven devices and vehicles, and using various interest rates and energy price changes were calculated to find present values that range from $2,057.13 to $8,213.64 (analysis from 2009).

It is also possible to combine solar PV with other technologies to make hybrid systems, which enable more stand alone systems. The calculation of LCOEs becomes more complex, but can be done by aggregating the costs and the energy produced by each component. As for example, PV and cogen and batteries while reducing energy- and electricity-related greenhouse gas emissions as compared to conventional sources.

### Solar thermal

LCOE of solar thermal power with energy storage which can operate round the clock on demand, has fallen to AU$78/MWh (US$61/MWh) in August 2017. Though solar thermal plants with energy storage can work as stand alone systems, combination with solar PV power can deliver further cheaper power. Cheaper and dispatchable solar thermal storage power need not depend on costly or polluting coal/gas/oil/nuclear based power generation for ensuring stable grid operation.

When a solar thermal storage plant is forced to idle due to lack of sunlight locally during cloudy days, it is possible to consume the cheap excess infirm power from solar PV, wind and hydro power plants (similar to a lesser efficient, huge capacity and low cost battery storage system) by heating the hot molten salt to higher temperature for converting the stored thermal energy in to electricity during the peak demand hours when the electricity sale price is profitable.

### Wind power

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Current land-based wind
In the windy great plains expanse of the central United States new-construction wind power costs in 2017 are compellingly below costs of continued use of existing coal burning plants. Wind power can be contracted via a power purchase agreement at two cents per kilowatt hour while the operating costs for power generation in existing coal-burning plants remain above three cents.

Current offshore wind
In 2016 the Norwegian Wind Energy Association (NORWEA) estimated the LCoE of a typical Norwegian wind farm at 44 €/MWh, assuming a weighted average cost of capital of 8% and an annual 3,500 full load hours, i.e. a capacity factor of 40%. NORWEA went on to estimate the LCoE of the 1 GW Fosen Vind onshore wind farm which is expected to be operational by 2020 to be as low as 35 €/MWh to 40 €/MWh. In November 2016, Vattenfall won a tender to develop the Kriegers Flak windpark in the Baltic Sea for 49.9 €/MWh, and similar levels were agreed for the Borssele offshore wind farms. As of 2016, this is the lowest projected price for electricity produced using offshore wind.

Historic levels
In 2004, wind energy cost a fifth of what it did in the 1980s, and some expected that downward trend to continue as larger multi-megawatt turbines were mass-produced. As of 2012[update] capital costs for wind turbines are substantially lower than 2008–2010 but are still above 2002 levels. A 2011 report from the American Wind Energy Association stated, "Wind's costs have dropped over the past two years, in the range of 5 to 6 cents per kilowatt-hour recently.... about 2 cents cheaper than coal-fired electricity, and more projects were financed through debt arrangements than tax equity structures last year.... winning more mainstream acceptance from Wall Street's banks.... Equipment makers can also deliver products in the same year that they are ordered instead of waiting up to three years as was the case in previous cycles.... 5,600 MW of new installed capacity is under construction in the United States, more than double the number at this point in 2010. 35% of all new power generation built in the United States since 2005 has come from wind, more than new gas and coal plants combined, as power providers are increasingly enticed to wind as a convenient hedge against unpredictable commodity price moves."

This cost has additionally reduced as wind turbine technology has improved. There are now longer and lighter wind turbine blades, improvements in turbine performance and increased power generation efficiency. Also, wind project capital and maintenance costs have continued to decline. For example, the wind industry in the USA in 2014 was able to produce more power at lower cost by using taller wind turbines with longer blades, capturing the faster winds at higher elevations. This opened up new opportunities in Indiana, Michigan, and Ohio. The price of power from wind turbines built 300 to 400 ft (91 to 122 m) above the ground can now compete with conventional fossil fuels like coal. Prices have fallen to about 4 cents per kilowatt-hour in some cases and utilities have been increasing the amount of wind energy in their portfolio, saying it is their cheapest option.