Session 25 Case Study – Residential System, Part 2 Operation and Analysis December 01, 2015

Session 25 - Value to class members Additional evaluation and analysis of a residential grid-tied PV systems o Operation o Life Cycle Costing o Payback Analysis 2

Grid-Tied PV Systems – The Design Process Design Steps in a Residential Scale System 1. Examination of site and estimation of performance 2. Securing financing 3. Carrying out PV system engineering and design 4. Securing relevant permits 5. Construction 6. Inspection 7. Connection to the grid 8. Performance monitoring 3

Grid-Tied PV Systems – The Design Process Step 5 – Construction Step 6 – Inspection Step 7 – Connection to the grid Step 8 – Performance monitoring 4

Comparison of Two Residential PV Systems 5kW system installed in 2010 Roof mounted 22 Siliken 225W poly modules Sunny Boy 4kW inverter No remote monitoring Installed cost: $28,979 $5.85/W (dc) Incentives: Utility co. rebate: $13,365 Federal ITC: $8,694 State Solar Incentive: $1,000 Total OOP Cost: $5,920 $1.20/W (dc) 3.5kW system to be installed in 2014 Elevated structure 14 Canadian 250W poly modules 14 Enphase micro-inverters o Enphase monitoring solution Installed cost: $13,450 o $3.84/W (dc) Incentives: Installer rebate: $1,000 Federal ITC: $4,035 State Solar Incentive: $1,000 Total OOP Cost: $7,415 $2.12/W (dc) 5

Step 8 – Performance monitoring 6 on-peak c/kWh; off-peak – 2.3c/kWh; average – 8c/kWh All electricity costs – 12.3c/kWh

Step 8 – Performance monitoring 7

Economic Analysis Current residential PV system example Assume that the installed cost of a 3.5kW PV system is $2.12/W after all incentives are accounted for. Assume that the system will produce an annual electrical amount of 6250 kWh (as measured). Assume the utility cost of electricity as $0.123/kWh. The plan here is to calculate the Life Cycle Cost (the numerator of the LCOE equation) on both an annualized and cumulative basis, and see when it crosses zero

Current residential PV system example A spreadsheet was used to analyze this situation; plotting the results yields (for annual return)

Current residential Plotting the cumulative return for 25 years Payback – 8.5 years

Net Metering 11 At the end of each month, a utility bill is calculated: Generation = N(kWh from utility) – N(kWh to utility) – N(some credits from previous month) This is all at the retail rate

Net Metering 12 Once a year, the residual credits are cashed in This is all at the wholesale rate For APS solar customers, the “settle-up” date is 12/31 For SRP solar customers, the date is 04/30 This is a critical difference

Step 8 – Performance monitoring 13 APS Net Metering

Step 8 – Performance monitoring 14 APS Net Metering – Generation Bill Avoided Electricity Cost = 0.123$/kWh * 5225kWh = $643

Step 8 – Performance monitoring 15 SRP Net Metering Avoided Electricity Cost = $643 - $130 = $513

Revised Economic Analysis Revised current residential PV system examples Assume that the installed cost of a 3.5kW PV system is $2.12/W after incentives, or $7415. Assume that the system will produce a net electricity reduction amount through net metering of 5225 kWh (APS calculation), or 4168 kWh (SRP calculation). Assume the utility cost of electricity is $0.123/kWh and does not increase over the lifespan of the PV system. The plan here is to calculate the Life Cycle Cost (the numerator of the LCOE equation) on both an annualized and cumulative basis, and see when it crosses zero

Revised current residential Payback –> 10.5 – 13.5 years