1. Costs and Benefits of a Solar-Assisted Hot Water System Carl D
Costs and Benefits of a Solar-Assisted Hot Water System Carl D. Martland Sugar Hill, NH

2. Ideal Location:
Southern exposure
Roof with 45-degree angle

3. Glycol is pumped up from the basement, circulates through the panels, and returns to the basement.
Glycol warms up as it circulates through tubes enclosed within each of two insulated panels.

4. Hot water comes out of the top of the tank.
Electric coil in top of tank (back up to solar system).
Warm fluid enters the bottom of an 80-gallon hot water, circulates through a maze of pipes, and is pumped back to the roof.
Thermostat
Overflow pipe
Pump
Expansion Tank

5. Hot water comes from the top of the tank
Cold water can be mixed with hot water to send water to house at desired temperature (e.g. 120 degrees)
Temperature of hot water coming from the tank

6. Temperature at the Collector and in the Tank: the Pump Runs if it is at Least 10 degrees warmer at the roof

7. Timing for Using Electricity
Event 2: off at 10:07 am
Event 3: on at 1:00 pm

8. Cost of System: $11,829 $11,829 Materials $7,463 Solar Panels (two)
$3,202
80-gallon solar/electric tank
$2,177
Pump, pipes, tubing, valves, glycol, insulation, controllers, etc.
$2,084
Installation of solar system
$3,350
Preparation of roof for installation
$950
Professional installation of panels
$2,400
Electrician
$385
Plumber
$631
Total
$11,829

9. Net Cost After Rebates: $6,780
Cost of System
$11,829
Credits
$5,049
State renewable energy rebate
$1,500
Federal tax credit (30%)
$3,549
Net Cost
$6,780

10. Typical Tempteratures of Glycol and Hot Water in 2012/2013 (clear days or days with some sun or light clouds)

11. Tank Temperature on Clear Days (hours of sunlight more important than temperature)

12. Tank Temperature on Cloudy Days

13. Energy Savings: $620/year
Oil Saved (gallons/year)
190
Price/gallon
$3.89
Savings per year
$740
Added electricity (kwh/year)
800
Price/kwh
$0.15
Added cost per year
$120
Net Annual Savings
$620

14. Return on Investment (ROI): 9.1% in the First Two Years
Cost of Installed System
$6,780
Annual Maintenance $0
Annual Net Energy Savings
$620
Estimated Net Benefit
ROI
9.1%

15. Estimated ROI Over Life of System: Cash Purchase
Cost of Installed System
$6,780
Annual Maintenance (equivalent annual cost)
$50
Annual Net Energy Savings
$620
Estimated Net Benefit
$570
ROI
8.4%

16. Estimated ROI Over Life of System: Borrowing 70% of Initial Expense
Cost
Benefit
Net Cost of Installed System
$6,780
Home equity loan (20 years, 4%)
$4,780
Net Investment
$2,000
Reserved for maintenance
($50)
Annual Loan Payment
($350)
Annual Net Energy Savings
$620
Annual Net Savings
$220
ROI
11%

17. Conclusions The system works as expected:
Installation completed on time and on budget
No operating problems
System supplies nearly all hot water from May through September and during good weather the rest of the year
It was a good investment for us:
State rebate and federal tax credit reduced initial expense by more than 40%
ROI greater than 8%

18. Costs and Benefits of a Solar-Assisted Hot Water System
Carl D. Martland
November 12, 2014