Solar FAQ

1. What is the difference between solar thermal and solar photovoltaic systems?

2. How much of the cost of the system do the incentives offset?

3. How large will the solar storage tank be?

4. How many collectors will go on my roof and how big are they?

5. Can the collectors be ground-mounted?

6. How much will my bill be offset?

7. Can an instantaneous/on-demand/tankless water heater be used as backup?

8. How much electricity does the solar pump use?

9. Do I need a south-facing or certain type of roof?

10. How much am I spending on water heating?

11. What happens when there is no sun?

12. What type of maintenance is required for solar thermal systems?

13. Are there financing options available for solar thermal systems?

14. How do I know solar thermal technology won’t become obsolete?

15. How much will a solar water heating system offset my carbon footprint?

16. Can a solar thermal system be used in conjunction with a solar photovoltaic system?

 

1. What is the difference between solar thermal and solar photovoltaic systems?
Solar energy can be harnessed as electricity or as thermal energy (heat). Due to the relative inefficiency of solar photovoltaic panels, solar thermal energy is the much more cost effective renewable energy option. The amount of space necessary for a solar thermal system is minimal compared to the required space for a properly sized solar photovoltaic system for the same building. The upfront costs and proportionate offset costs from incentives also weigh in favor of solar thermal systems. Whereas a photovoltaic panel will degrade over its lifetime, reducing its power output, solar thermal collectors do not degrade in efficiency over time, and can last over forty years if properly maintained.

2. How much of the cost of the system do the incentives offset?
The incentive amounts for solar thermal systems vary, and are increased for commercial projects.  Homeowners should expect to offset about 50-75% of the costs of the system with the CSI-Thermal rebate and the Federal Tax Credit.  Business owners can offset anywhere from 40-80% of the costs through the various incentives available, including the increased CSI-Thermal incentive and the Business Investment Tax Credit.

3. How large will the solar storage tank be?
The volume of the solar storage tank is determined by the daily hot water load of the building.  The goal is to store as much hot water as will be used everyday.  With that said, an average family of four will use about 60-80 gallons of hot water daily, and a standard size solar tank for residential applications is 80 gallons.  For commercial applications, the size of the solar storage tank(s) will vary, and up to 5,000 gallons can be stored in one solar tank.

4. How many collectors will go on my roof and how big are they?
The number of collectors for each system is also determined by the daily hot water load of the building.  An average residential system will consist of 1-3 collectors, each ranging from 20-30 ft2 in size.  Commercial systems will include larger arrays of collectors, with banks of up to six collectors plumbed in series.  Our commercial collectors can heat about 65 gallons of water per day on average in Southern California.

5. Can the collectors be ground-mounted?
Yes, the collectors can be secured to a ground-mounted support structure.  The most important thing is that the structure that the collectors are being fastened to is designed correctly for the weight load and the wind load.  Our engineers will create an aesthetically pleasing and structurally sound racking solution for your solar thermal system.

6. How much will my bill be offset?
For residential systems, water heating costs can be reduced by up to 95% annually, depending on the backup heat source.  With commercial systems, you can expect up to 80% reduction in water heating costs on an annual basis, depending on hot water load, location, and load profile.

7. Can an instantaneous/on-demand/tankless water heater be used as backup?
Yes, an instantaneous water heater can be used as a backup heat source for solar thermal systems.  It must be advanced enough to handle incoming hot water without errors or faults, but will continue to operate similarly.  Instantaneous water heaters are the best backup for solar thermal, because they do not experience standing heat loss, only heating on demand.  With hard water conditions these types of water heaters will become inefficient quickly due to scaling and calcification, mainly due to the rapid heating of the hard water.  The amount of rapid heating is greatly reduced when used in conjunction with a solar thermal system, so the useful lifetime of instantaneous water heaters is also extended.

8. How much electricity does the solar pump use?
The solar pump for residential systems will only use about 75-100 kWh annually, depending on the hot water load and demand.  Commercial solar pumps are larger and will use more electricity, but the pressurized closed loop allows the pumps to be relatively low-powered.  The amount of electricity used for the solar pump will be minimal compared to the energy offset for water heating by the solar thermal system.

9. Do I need a south-facing or certain type of roof?
Although orientating the collectors in a south-facing position is optimal, it is not required and roofs facing in any direction can be used.  The collectors can also be mounted on any type of roof; our innovative racking systems allow easy installations on even the toughest tile roofs.  For commercial roofs, especially membrane-type roofs, penetration-free ballast racking systems are also available.

10. How much am I spending on water heating?
This depends on what type of water heater you have, what type of fuel you are using, and what rate you are paying for that fuel.  An average family of four with a 50-gallon natural gas water heater will use about 20-30 therms per month to heat water.  Therm prices spike and will vary, for example residential prices have gone from $1.75/therm price in July 2008 to the current price of around $1.00/therm due to domestic discoveries of natural gas.   Electricity is about 3-4 times less efficient than natural gas for water heating, and propane is about 3 times less efficient at current energy rates.

11. What happens when there is no sun?
When the sun is not shining or it is nighttime, the backup heat source is used to heat the water.  Solar thermal systems will always require a backup heat source.  When used in combination with a solar photovoltaic system and an electric water heater, although not recommended, you can achieve “net-zero” energy water heating.

12. What type of maintenance is required for solar thermal systems?
Maintenance for solar thermal systems is minimal, and will depend on the system type.  Closed loop antifreeze systems will require annual testing of the heat transfer fluid, and will require a flush and refill every 5-10 years.  Drainback systems and ICS systems are virtually maintenance-free due to their unique designs.  Pumps will need replacement every 15-20 years.  The collector array should be cleaned routinely for optimal system performance.

13. Are there financing options available for solar thermal systems?
Yes, we have four financing options that can reduce or eliminate upfront system costs.  We offer leasing, energy purchase agreements (third-party ownership), low-interest amortized loans, and Property Assessed Clean Energy (PACE) financing.

14. How do I know solar thermal technology won’t become obsolete?
Solar thermal technology has reached the apogee of design, and in the next ten or twenty years will not change much for solar water heating systems.  The collectors are very efficient, and system designs have been proven and tested in the residential and commercial markets.

15. How much will a solar water heating system offset my carbon footprint?
This depends on what type of fuel you are currently using to heat your water.  For those burning natural gas, every therm used releases 11.2 lbs of CO2 into the atmosphere.  Over the lifetime of an average residential system, over 50 tons of CO2 will be offset.

16. Can a solar thermal system be used in conjunction with a solar photovoltaic system?
Yes, solar thermal systems are completely separate and independent of solar photovoltaic systems.  For residential applications, a solar photovoltaic DC-powered pump may be used.

 
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