INSTALLED SYSTEM COST CALCULATOR
System and modules
Prices and costs
Sweep efficiency from %
constant module price in $
constant module price in $/Wp
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This calculator determines the cost to install a PV system based on the properties of the PV modules and the balance of systems (BOS) costs.
It is common to compare PV modules in terms of dollars per peak watt ($/Wp); that is, by the price paid for a module divided by the power it produces under standard measurement conditions. The benefit of this metric is that it is simple, and that it helps to compare modules of different sizes and efficiencies.
The problem with comparing modules in $/Wp, however, is that PV electricity is not generated by modules alone. A PV installation also requires land, frames, labour, wiring, inverters, and other electronics, all of which are lumped under the term, Balance of Systems (BOS). These BOS costs depend on the efficiency and the structure of the PV modules.
In general, comparing the price of PV modules on a $/Wp basis makes higher efficient modules appear less cost-effective than they really are.
For example, if one could purchase a 10% module for $100, or 20% module for $200, and both modules had the same area of 1 m2, then on a $/Wp basis, the modules would cost the same: 1 $/Wp (see equations below). Yet this does not mean that a PV installation using the 10% modules would cost the same as one using the 20% modules.
Consider the installation of a 20 kWp PV power plant. One could either install 100 m2 of the 20% modules or 200 m2 of the 10% modules. It would clearly be cheaper to use the 20% modules, since that would require less land, less labour, and fewer frames, all of which make up a significant fraction of the cost of an installed system.
There can also be structural differences that make one panel superior to another, but which are not entailed in the $/Wp metric. For example, lighter panels might incur lower transportation and framing costs, annd flexible panels might be quicker to install.
BOS costs vary significantly from one application to another, and from one country to another, so they cannot be evaluated with a generic value or fraction. Nevertheless, BOS costs should not be neglected because they typically contribute to more than half of the cost to install a PV system.
It is pertinent to note here that the value of a PV module does not affect the installation cost alone. Different types of modules also repond differently to changing operating conditions (temperature, spectra, intensity), they degrade at different rates, they have different failure modes, they require different degrees of maintenance, and so forth. These operational aspects are not encompassed by this calculator, which is specific to installed PV costs. Thus, the installed PV cost is one step superior to comparing module prices in terms of $/Wp, but more analysis is required to give a complete assessment of a module's value to a PV installation.
The installed system cost Csys is given by:
Csys = Nmod ⋅ Cmod + CBOS,
where Nmod is the number of installed modules, Cmod is the cost of each module (assuming all modules are identical), and CBOS is the cost of the balance of systems.
The number of modules Nmod is equal to the system power Psys divided by the module power Pmod, where the latter depends on the efficiency ηmod and area Amod of each PV module:
Nmod = Psys / Pmod =
Pmod / ( ηmod ⋅ Amod ⋅ 1 kWp/m2).
The balance of systems cost CBOS is rather complicated to calculate as it is comprised of many factors: e.g., labour, frames, cabling, inverters, insurance, transportation, land. In this calculator, they are simply represented by three variables:
CA, BOS costs that scale with area in $/m2. Examples are (i) a fraction of the labour since it takes longer to mount and wire more modules, (ii) mounting frames, (iii) cabling per module, and (iv) land or roof area.
CP, BOS costs that scale with system power in $/Wp. This includes aspects of the inverter since it typically becomes more expensive to transform more DC power into AC power. Inverter costs are indpendent of the system area.
CF, BOS costs that are fixed and independent of the system size or power. These can include some administration costs and other aspects to labour, the inverter, and cabling between modules and inverter.
Hence, the BOS costs can be represented by the equation,
CBOS = Nmod ⋅ Amod ⋅ CA +
Psys ⋅ CP + CF.
Although it is well known that a comparison of modules prices on a $/Wp basis makes a high efficiency module appear less cost-effective than it really is, such comparisons are widely used because (i) they are simple, and (ii) there is not a set of BOS costs generally accepted by the PV industry as being representative for a particular application. With this calculator, we would like to list a series of case studies that can be used for this purpose.
Case studies that break down BOS costs are rarely published because they are confidential to installation companies.
One case study published in 2010 was specific to 1.5 kWp residential rooftop systems installed in Canberra, Australia, in 2010 . It concluded that CA = 190 +/– 50 AUD/m2, CP = 0.62 +/– 0.10 AUD/Wp, and CF = 1500 +/– 400 AUD. CA is high for small roof-top systems such as these because of the significant labour associated with their installation; in this study, CA is compounded by the high labour costs prevalent in Australia.
If any other published case studies are forwarded to firstname.lastname@example.org
Please email corrections, comments or suggestions to email@example.com.
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Welcome to the installed system cost calculator
This calculator calculates the cost to install a PV system based on the price, efficiency and area of its PV modules, as well as the balance of systems (BOS) costs.
BOS costs vary significantly from one application to another, and from one country to another. They can also vary rapidly over time. The default costs employed by this calculator, and the costs contained in the case studies listed within, should not be assumed to represent the BOS costs of any given PV installation.
The assumptions used in the calculations are described on the ''About'' page.
Neither PV Lighthouse nor any person related to the compilation of this calculator make any warranty, expressed or implied, or assume any legal liability or responsibility for the accuracy, completeness or usefulness of any information disclosed or rendered by this calculator.
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