# Comparative PV LCOE Calculator Documentation

This documentation will help you start using the Comparative Photovoltaic (PV) Levelized Cost of Energy (LCOE) Calculator.

## Getting Started

This tool is designed for making comparisons between a baseline and a proposed technology.

The calculator is preloaded with reasonable default values for every parameter. Try dragging a slider or changing a numeric input and watch the LCOE values in the results section change immediately.

##### Example: Cell cost reduction

In the proposed section, drag the cell cost slider or type in the cell cost numeric input field to reduce its value by about 50%. The proposed LCOE immediately changes, but by less than 50%. LCOE depends on a lot more than just cell cost!

You can also do quick breakeven analysis of technology improvements.

##### Example: New technology breakeven analysis

Simulate adding a new component to the module by changing the cost of the extra component in the proposed section to 4.00 USD/m2. The proposed LCOE increases due to the higher module cost.

Suppose the new component increases the energy yield of the system. In the proposed section, drag the energy yield slider until the proposed LCOE equals the baseline LCOE. This shows how much of an improvement to energy yield the new technology must provide to break even in LCOE.

## Presets

The calculator includes hundreds of presets for the input parameters. To replace the baseline input parameters with a set of preset parameters, use the presets button. To update the proposed inputs to match the preset, use the copy from baseline button after choosing a preset.

Each preset represents a simulated PV system with a particular cell technology, module package type, system type, and geographic location. Input values for module cost come from NREL's benchmark module cost studies. Energy yield has been simulated using SAM with TMY inputs for each location. Silicon modules are simulated with an anti-reflective coating (ARC) on the glass.

Cell technology
Cell technology can be monocrystalline silicon (mono-Si), multicrystalline silicon (multi-Si), or cadmium telluride (CdTe). Cell technology affects cell cost, efficiency, energy yield, degradation rate, BOS cost, and the available values for package type and system type.
Package type
Package type can be (glass-polymer backsheet) or (glass-glass). Crystalline silicon modules are most often the glass-polymer backsheet type, but glass-glass modules are commercially available. CdTe modules are not available in the glass-polymer backsheet package. Package type affects back layer cost.
System type
System type can be (fixed tilt, utility scale), (single-axis tracked, utility scale), or (roof-mounted, residential scale). Our baseline utility-scale system has 100 MW capacity and our baseline residential-scale system has 5.6 kW capacity. System type affects energy yield and BOS cost.
Location
Location can be one of 50 places, one in each US state. Locations are chosen to have nearly the median solar resource in the state, subject to data availability. TMY2 or TMY3 datasets were used in each location to produce a preset value for first-year energy yield. Location affects energy yield and BOS cost.

## Input Parameters

### Separate inputs

These inputs apply separately to the baseline and proposed technologies. Module price is calculated by summing the component costs and adding a 15% margin representing the module manufacturer's profit.

#### Cost

Front layer cost
Cost of the glass on the front surface of the module.
Cell cost
Cost of PV cells. In the case of crystalline silicon modules, complete cells are included but interconnects are not. In the case of CdTe modules, the entire monolithically integrated cell layer is included.
Back layer cost
Cost of the polymer or glass layer on the back of the module.
Non-cell module cost
Cost of encapsulation, cell interconnection, junction box, leads, connectors, nameplate, frame, and testing.
Extra component cost
Initially set to zero, this cost represents an additional component, not otherwise accounted for, being proposed for addition to the module or system.
O&M cost
Cost of operations and maintenance, including troubleshooting, repairs, and cleaning. This cost is normalized to the system's nameplate power.
BOS cost, power-scaling
The component of balance of system cost that scales with the power output of the system, regardless of its physical size. This includes the inverter, for instance.
BOS cost, area-scaling
The component of balance of system cost that scales with the physical size of the system. This includes racking, wiring, and installation labor, for example.

#### Performance

Efficiency
Module efficiency measured at standard test conditions (STC). This is the module's nameplate efficiency.
Energy yield
Also known as array yield, the first-year energy production of the system, normalized by its nameplate power rating.

#### Reliability

The annual, fractional loss of the system's energy production.
Service life
The number of years the system is expected to operate.

### Common inputs

#### Financial

Discount rate
The annual rate at which future costs and future energy production are discounted.

## Calculation

The calculator performs a “simple” LCOE calculation. $$\text{LCOE}=\frac{\sum_{n=0}^{n_s}{\frac{c_n}{\left( 1 + d \right)^n}}}{\sum_{n=0}^{n_s}{\frac{e_n}{\left( 1 + d \right)^n}}}\text{, }$$ where $$c_n$$ is the cost in year $$n$$, $$d$$ is discount rate, $$e_n$$ is the energy produced in year $$n$$, and $$n_s$$ is the number of years in the system's service life.

The cost in year $$n$$ $$c_n = \begin{cases} c_\text{capital} & n = 0 \\ c_\text{O&M} & n > 0 \end{cases}\text{,}$$ where $$c_\text{capital}$$ is the initial capital cost of the system and $$c_\text{O&M}$$ is the annual O&M cost. In this calculator, these costs are in units of USD/kW.

The energy produced in year $$n$$ $$e_n = \begin{cases} 0 & n = 0\\ \text{max}\left[ Y \left( 1 - R_d \right)^\left(n-1\right), 0 \right] & n>0 \end{cases}\text{,}$$ where $$Y$$ is the first-year energy yield and $$R_d$$ is the system's annual degradation rate. In this calculator, this energy production is in units of kWh/kW, so $$c_e$$ is in units of USD/kWh.

This tool is for evaluating how changes to PV module and system technology affect LCOE. You may be interested in these other resources.

If you're looking for a calculation that includes an explicit energy output prediction, and/or has more detailed financial models, consider using the System Advisor Model, which also calculates LCOE, or PVWatts.

The Annual Technology Baseline provides historical, current, and forecast cost information for all types of energy technology, including LCOE data for PV.

Tools with fewer technology-specific details and more financial details include REopt, which also includes energy storage, and the simple LCOE Calculator.

## Data Sources

Input values for module cost breakdowns and balance-of-system costs come from NREL's benchmark analysis. Results are relevant to systems installed in the United States. The latest available studies are used:

Silicon module inputs and balance-of-system costs: Fu, Ran, David Feldman, Robert Margolis, Mike Woodhouse, and Kristen Ardani. 2017. U.S. Solar Photovoltaic System Cost Benchmark: Q1 2017. Golden, CO: National Renewable Energy Laboratory. NREL/TP-6A20-68925. https://www.nrel.gov/docs/fy17osti/68925.pdf.

CdTe: Model last updated in 2017, unpublished.

Default values for degradation rates for each technology are the median values published in:

D. Jordan and S. Kurtz, "Photovoltaic Degradation Rates - An Analytical Review," Progress in Photovoltaics: Research & Applications 21(1), pp. 12-29, 2013.

## Source Code

The calculator is powered by a JavaScript file that is available online.