
I received a quickie quote from the solar panel company we are working with here in Seattle that is based on satellite images of our house just to give us an idea of how much it would cost. If we want to move forward, they'll come out and update the estimate after looking at our roof and various other variables.
In the quote, they included three PV options, ranging in size from 4.6 to 5.3 kW, using three different types of modules. They are assuming 99% annual solar access on a south-facing array (providing about 1144 kWh/yr per kW). Again, these are ballpark figures, but you'll get the idea.
Option 1 has high power density, but a small incentive rate
This option has the maximum power in the smallest possible footprint, and the system production will pay back about 71% of the initial investment (after the tax credit) by the end of 2020 through a combination of state production incentive and net metering (including the value of all the electricity we won't have to buy).
Annual production for this option is estimated at 6043 kWh, earning $906 per year while offsetting roughly 47% of our reported usage.
Option 2 has a low initial cost, but a small incentive rate
The second option has lower power density which means the panels take up more space on our roof, but the lower price per watt makes this the least expensive system in terms of up-front cost. The system production will pay back about 83% of the initial investment by the end of 2020.
Annual production for this option is estimated at 5264 kWh, earning $790 per year while offsetting roughly 41% of our reported usage.
Option 3 has a very high incentive rate, but a higher initial cost
The last option has components that are all made in Washington, which makes them eligible for the top incentive rate of 54 cents per kWh. As a result, these systems usually pay for themselves more quickly than other products, despite the higher up-front cost. We would break even in year nine, earning about $5169 by the end of year ten.
Annual production for this option is estimated at 5356 kWh, earning $2892 per year while offsetting roughly 41% of our reported usage.
Here's part of the breakdown (since it's easier to see the stats back to back):
Option 1System size: 5280 watts
Estimated Production (kWh/yr): 6043
Installed Cost: $30,030.45
Dollars per Watt: $5.69
30% Federal Tax Credit: -$9,009.14
Net Cost After Tax & Credit(s):
$21,021.32Production Incentive, $/kWh: $0.15
Annual Incentive Payment: -$906.45
Total Incentive thru June 2020: -$8,611.28
Net residual cost (including net metering offset) as of 2020: $6,067.38
% of cost paid back by 2020: 71.1%
Payback Time (years): 18
Option 2System size: 4600 watts
Estimated Production (kWh/yr): 5264
Installed Cost: $22,408.97
Dollars per Watt: $4.87
30% Federal Tax Credit: -$6,722.69
Net Cost After Tax & Credit(s):
$15,686.28Production Incentive, $/kWh: $0.15
Annual Incentive Payment: -$789.60
Total Incentive thru June 2020: -$7,501.20
Net residual cost (including net metering offset) as of 2020: $2,660.04
% of cost paid back by 2020: 83.0%
Payback Time (years): 15
Option 3System size: 4680 watts
Estimated Production (kWh/yr): 5356
Installed Cost: $39,899.05
Dollars per Watt: $8.53
30% Federal Tax Credit: -$11,969.72
Net Cost After Tax & Credit(s):
$27,929.34Production Incentive, $/kWh: $0.54
Annual Incentive Payment: -$2,892.24
Total Incentive thru June 2020: -$27,476.28
Net residual cost (including net metering offset) as of 2020: -$5,168.54
% of cost paid back by 2020: 118.5%
Payback Time (years): 9
I'm more partial to Option 3 because of the quick payoff and the incentives. After 9 years, all energy generated will be "free". Option 1 has its perks in that it can squeeze more panels into a smaller space, but it takes forever to pay off. Another objective for us would be to reduce the amount of energy we use to meet the amount generated. I'm sure we can close the gap with some effort.
In any case, we have some figgerin' to do. I'll let you know if we move forward and you'll get the play-by-play if we do!