Calculate costs and savings in TypeScript

European Economic Area (EEA) developers

You can create your own calculations using TypeScript. The code at the bottom of this page helps you determine whether it's cheaper in the long run to install solar panels or continue paying your electricity bill as is.

Here's a high-level breakdown of how the code determines solar panel costs.

Part 1: System needs and setup

First, define your current electricity usage and bills:

How much electricity do you use each month? ( monthlyKwhEnergyConsumption )
How much does that electricity cost? ( energyCostPerKwh )

Next, enter your solar system plans:

How many panels? ( panelsCount )
How powerful are the panels? ( panelCapacityWatts )
How much does installation cost? ( installationCostPerWatt )
Any discounts on the system? ( solarIncentives )

Part 2: Calculations

Based on the inputted values, the code calculates:

yearlyProductionAcKwh : The total annual electricity your solar panels can generate.
totalCostWithSolar : The cost of electricity over many years withsolar panels.
totalCostWithoutSolar : The cost of electricity over many years withoutsolar panels.

Part 3: Results

The code also tells you the following:

savings : The difference between the cost with and without solar panels.
breakEvenYear : How many years until the cost of solar panels equals the savings on electricity.

Example code

 // Solar configuration, from buildingInsights.solarPotential.solarPanelConfigs 
 let 
  
 panelsCount 
  
 = 
  
 20 
 ; 
 let 
  
 yearlyEnergyDcKwh 
  
 = 
  
 12000 
 ; 
 // Basic settings 
 let 
  
 monthlyAverageEnergyBill 
 : 
  
 number 
  
 = 
  
 300 
 ; 
 let 
  
 energyCostPerKwh 
  
 = 
  
 0.31 
 ; 
 let 
  
 panelCapacityWatts 
  
 = 
  
 400 
 ; 
 let 
  
 solarIncentives 
 : 
  
 number 
  
 = 
  
 7000 
 ; 
 let 
  
 installationCostPerWatt 
 : 
  
 number 
  
 = 
  
 4.0 
 ; 
 let 
  
 installationLifeSpan 
 : 
  
 number 
  
 = 
  
 20 
 ; 
 // Advanced settings 
 let 
  
 dcToAcDerate 
  
 = 
  
 0.85 
 ; 
 let 
  
 efficiencyDepreciationFactor 
  
 = 
  
 0.995 
 ; 
 let 
  
 costIncreaseFactor 
  
 = 
  
 1.022 
 ; 
 let 
  
 discountRate 
  
 = 
  
 1.04 
 ; 
 // Solar installation 
 let 
  
 installationSizeKw 
 : 
  
 number 
  
 = 
  
 ( 
 panelsCount 
  
 * 
  
 panelCapacityWatts 
 ) 
  
 / 
  
 1000 
 ; 
 let 
  
 installationCostTotal 
 : 
  
 number 
  
 = 
  
 installationCostPerWatt 
  
 * 
  
 installationSizeKw 
  
 * 
  
 1000 
 ; 
 // Energy consumption 
 let 
  
 monthlyKwhEnergyConsumption 
 : 
  
 number 
  
 = 
  
 monthlyAverageEnergyBill 
  
 / 
  
 energyCostPerKwh 
 ; 
 let 
  
 yearlyKwhEnergyConsumption 
 : 
  
 number 
  
 = 
  
 monthlyKwhEnergyConsumption 
  
 * 
  
 12 
 ; 
 // Energy produced for installation life span 
 let 
  
 initialAcKwhPerYear 
 : 
  
 number 
  
 = 
  
 yearlyEnergyDcKwh 
  
 * 
  
 dcToAcDerate 
 ; 
 let 
  
 yearlyProductionAcKwh 
 : 
  
 number 
 [] 
  
 = 
  
 [... 
 Array 
 ( 
 installationLifeSpan 
 ). 
 keys 
 ()]. 
 map 
 ( 
  
 ( 
 year 
 ) 
  
 = 
>  
 initialAcKwhPerYear 
  
 * 
  
 efficiencyDepreciationFactor 
  
 ** 
  
 year 
 , 
 ); 
 // Cost with solar for installation life span 
 let 
  
 yearlyUtilityBillEstimates 
 : 
  
 number 
 [] 
  
 = 
  
 yearlyProductionAcKwh 
 . 
 map 
 ( 
  
 ( 
 yearlyKwhEnergyProduced 
 , 
  
 year 
 ) 
  
 = 
>  
 { 
  
 const 
  
 billEnergyKwh 
  
 = 
  
 yearlyKwhEnergyConsumption 
  
 - 
  
 yearlyKwhEnergyProduced 
 ; 
  
 const 
  
 billEstimate 
  
 = 
  
 ( 
 billEnergyKwh 
  
 * 
  
 energyCostPerKwh 
  
 * 
  
 costIncreaseFactor 
  
 ** 
  
 year 
 ) 
  
 / 
  
 discountRate 
  
 ** 
  
 year 
 ; 
  
 return 
  
 Math 
 . 
 max 
 ( 
 billEstimate 
 , 
  
 0 
 ); 
  
 // bill cannot be negative 
  
 }, 
 ); 
 let 
  
 remainingLifetimeUtilityBill 
 : 
  
 number 
  
 = 
  
 yearlyUtilityBillEstimates 
 . 
 reduce 
 (( 
 x 
 , 
  
 y 
 ) 
  
 = 
>  
 x 
  
 + 
  
 y 
 , 
  
 0 
 ); 
 let 
  
 totalCostWithSolar 
 : 
  
 number 
  
 = 
  
 installationCostTotal 
  
 + 
  
 remainingLifetimeUtilityBill 
  
 - 
  
 solarIncentives 
 ; 
 console 
 . 
 log 
 ( 
 `Cost with solar: $ 
 ${ 
 totalCostWithSolar 
 . 
 toFixed 
 ( 
 2 
 ) 
 } 
 ` 
 ); 
 // Cost without solar for installation life span 
 let 
  
 yearlyCostWithoutSolar 
 : 
  
 number 
 [] 
  
 = 
  
 [... 
 Array 
 ( 
 installationLifeSpan 
 ). 
 keys 
 ()]. 
 map 
 ( 
  
 ( 
 year 
 ) 
  
 = 
>  
 ( 
 monthlyAverageEnergyBill 
  
 * 
  
 12 
  
 * 
  
 costIncreaseFactor 
  
 ** 
  
 year 
 ) 
  
 / 
  
 discountRate 
  
 ** 
  
 year 
 , 
 ); 
 let 
  
 totalCostWithoutSolar 
 : 
  
 number 
  
 = 
  
 yearlyCostWithoutSolar 
 . 
 reduce 
 (( 
 x 
 , 
  
 y 
 ) 
  
 = 
>  
 x 
  
 + 
  
 y 
 , 
  
 0 
 ); 
 console 
 . 
 log 
 ( 
 `Cost without solar: $ 
 ${ 
 totalCostWithoutSolar 
 . 
 toFixed 
 ( 
 2 
 ) 
 } 
 ` 
 ); 
 // Savings with solar for installation life span 
 let 
  
 savings 
 : 
  
 number 
  
 = 
  
 totalCostWithoutSolar 
  
 - 
  
 totalCostWithSolar 
 ; 
 console 
 . 
 log 
 ( 
 `Savings: $ 
 ${ 
 savings 
 . 
 toFixed 
 ( 
 2 
 ) 
 } 
 in 
 ${ 
 installationLifeSpan 
 } 
 years` 
 ); 
   SolarPotentialSection 
 . 
 svelte

Calculate costs and savings (non-US)