The ratios we analyse and how they are calculated

The data we hold on each project enables us to calculate a number of key parameters related to the design and intended performance of utility-scale solar power plants.

These are based on the published data for the project (often at the time of design or installation) so actual operational ratios may differ.



How calculated


Design performance ratio


Rated output capacity in MWAC ÷

Solar array capacity in MWP

Actual performance ratio will vary

Annual energy yield


Design output in MWh ÷

Rated output capacity in MWAC

Assuming standard irradiation levels

Equivalent households


Annual energy yield ÷ average house electricity consumption

Varies with energy intensiveness of local households

Emissions saving



Annual energy yield ÷ average carbon intensity of electricity

Varies depending on regional fuel mix for electricity generation

Equivalent cars



Emissions saving ÷ average annual emissions per car

Varies with regional fuel economy of vehicle fleet

Land area



Solar array (fenced) area ÷

Solar array capacity in MWP

Varies with latitude and type of mounting structure / tracking

Capital cost



Capital cost of project ÷

Rated output capacity in MWAC

Based on published completion or resale cost - not necessarily equivalent

Financial gearing


Non-equity finance ÷

Capital cost of project

Worldwide average ratios

The following table shows the worldwide averages as of March 2014.

Data for individual projects show that some ratios can vary substantially from these averages.




Performance ratio


Energy yield

1,830 hrs

Varies geographically from 1,380 in Europe to 2,645 in South America

Equivalent households

294 homes

<200 in N America to >450 in Asia

Emissions saving

712 tonnes

<300 in France with low fossil-fuelled electricity

Equivalent cars

215 cars

Only limited data for this ratio at present

Land area

2.7 Ha

Median is lower - some sites larger than needed

Capital cost


Decreasing from >$8m in 2008 to <$3m in 2014



Only limited data for this ratio at present

We can calculate many of these ratios on a regional basis for continents, countries and even provinces, and we include this data in selected reports as shown here.

Where factors change with time, we also calculate ratios on an annual basis.

Data analysis

The Wiki-Solar Database holds many different parameters


The authority on utility-scale solar power



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