DIY 10KW PV Electric Payback Calculations
System Design - On Line since January 2016
10KW System set up for Net Metering ( no batteries)
32 Panels roof mounted on standing seam metal roof
32 Micro Inverters
12KW DC to AC Inverter with 25yr warranty
How Net metering works:
I use power based on the loads I present to the PV system
surplus power spins my meter backwards and my neighbors use it.
When I use more power than I'm producing the meter runs forward.
My electric bill is $0 for ~8 months per year.
A separate production meter is reported to the SREC program monthly.
Massachusetts SREC program
Pays out 0.22 /kWh average for 10 years
Average Annual payout based on 35 months of operation $2,200/yr
Household Power Usage
24 Months before panels averaged 780kWh/month $155/month electric bill
35 months with panels on line $35/month electric bill
Electric Bill Savings $120/month; $1440/year
System Cost
DIY Installation (hardware only) $22,775
After 30% Federal Tax Credit $15,943
I designed and installed this system myself. This is not reasonable for most.
A Turnkey System cost would have been 50% higher at ~ $34,000
Turnkey Installation Cost $34,000
After 30% Federal Tax Credit $23,800
DIY System Payback
$15,943/($1,440 annual Elec bill savings + $2,200 SREC annual payout) = 4.38 years with SRECs
$15,943/$1,440 annual Elec bill savings= 11.07 years without SRECs
5.6 years remaining SREC payouts = 5.6*$2,200= $12,320
$12,320/$420 annual elec. bill = 29 years with no elec. bills after system is paid off.
Turnkey System Payback
$23,800/($1,440 annual Elec bill savings + $2,200 SREC annual payout) = 6.5 years with SRECs
$23,800/$1,440 annual Elec bill savings= 16.5 years without SRECs
Cost and efficiency losses not included the above calculations:
~ 6 weeks of design and installation work, this being my first and only design.
Panel peak power out drops ~ 3 %/yr and tapers off at about 70%
Estimated End of Panel Life is 25 years
Maintenance costs, to date these have been $0
Hardware costs keep dropping 2-3% /yr , these costs are based fall of 2015 prices
