Solar Thermal FAQ

If your basic questions are not answered here, please send us e-mail and tell us what's missing, superfluous or unclear. Thanks!

First... use this web page which presents a bit of information - still far from complete - about solar thermal (aka solar water heating or solar hot water) systems.

Second... fill out our secure CLIENT INFORMATION FORM for solar thermal systems. This gives us some basic information to begin to address your situation and serve you with much more personal follow-up. We appreciate your understanding and assistance with this.

If you want to see images and brief descriptions of systems that Renovus has installed, please refer to our solar thermal portfolio webpage.

How does solar water heating work (in our climate)?

Anyone who has ever turned on a garden hose left out in the summer sun knows that solar water heating works. In fact, there are probably as many low-tech, low-cost ways to create solar heated water as there are do-it-yourselfers and weekend plumbers. We encourage you to think about and even experiment with all the possibilities.

In our opinion, there is only one type of solar (domestic) hot water (SHW, SDHW) system that works well in a freezing climate - pressurized, closed loop systems. Although we have seen and thought about installing unpressurized drainback systems, at this point we do not consider them as reliable as pressurized, closed-loop designs.

In brief, solar heat energy is gathered by evacuated-tube or flat-plate solar collectors and moved (by a pump) into a dwelling, through a heat exchanger, and back to the collectors via a closed loop of copper pipe. The heat exchanger may be external to or integral to a dedicated solar hot water storage tank. The solar pre-heated water in this tank is transferred into the existing water heater whenever hot water is called for (from the existing tank). Being pre-heated by solar, less (or no) energy will be required of the conventional water heater to heat up the incoming solar hot water to a useful 110-120°F. Because solar pre-heated water can exceed this temperature (especially in the summer months), we install a mixing valve, pressure-temperature relief valves, and often a heat dissipation device in all SHW systems.

In the ideal case, we would prefer to provide solar pre-heated water to an on-demand or tankless backup water heater. This reduces the space requirements of having two potable water storage tanks and increases efficiency of the system significantly.

Can I use a solar thermal system to heat my house? My greenhouse?

The short answer to the first question is maybe if you already have (or plan to have) radiant floor heat distribution, but not without also having a backup heating system (usually a boiler). The answer to the second question is probably not (a good passive design is almost always preferable to any type of active heating system, solar or otherwise).

Any solar thermal space heating system will require a well thought out design tailored to the heat load demands of the space. Renovus has designed and installed such systems, but design time (including a detailed heat load analysis) and the costs thereof must be figured into the economics of such a project.

How much does it cost?

Rough costs for SDHW systems range from around $11,000 for 2-person installations (16 to 20 tube collector) to about $18,000 for 4-person systems (32 to 40 tubes) with considerable variation depending on the plumbing labor involved. Simple payback times realized through the energy savings are estimated at around 10 to 15 years depending on the inflation rate of the displaced conventional energy source (electric, gas, oil) during this period. However, bear in mind that a simple payback analysis does not take into consideration the intangible and unaccounted for benefits of 30 years of greatly reduced CO₂ emissions and nearly zero environmental impact.

So far, our cost estimates for solar primary heating systems (i.e., systems having a conventional boiler as backup) seem to be on a par with geothermal (ground-source) heating systems, but we do not yet have enough experience with such systems to feel comfortable giving even rough numbers here since so much depends on the building size and its heat load requirements.

NYS tax credits?

On August 1, 2005, Gov. Pataki signed new solar electric and solar water heating tax credit legislation into law. For details, see the official press release.

The legislation (S.4962-a) exempts the sale and installation of solar energy systems equipment from state sales and compensating use taxes, and gives municipalities the option of granting the local exemption.

A second bill (S.5252) broadens the existing solar electric generating equipment personal income tax credit to also include equipment utilizing solar radiation to provide heating, cooling and/or hot water and applies to taxable years beginning January 1, 2006. The bill also increases the maximum allowable credit to $5,000 starting September 1, 2006. The credit is currently capped at $3,750 for solar electric only. The personal income tax credit covers 25% of the qualified expenditures for the purchase and installation of the solar energy systems equipment.

Federal tax credits?

The following summaries are our current understanding of renewable energy provisions in the recently passed federal Energy Bill.

Commercial Solar Electric and Solar Water Heating: The Business Energy Tax Credit rises from 10% to 30% with no cap for solar electric and solar water heating systems placed in service between Jan. 1, 2006 and Dec. 31, 2007. This credit applies to the cost of the system after any incentives (e.g., NYSERDA) or government grants are applied.

For much more detail see Energy Policy Act of 2005 (Section 1336-1337) and 26 USC Section 48.

Residential Solar Electric and Solar Water Heating: The Energy Policy Act of 2005 (H.R. 6) establishes a 30% tax credit up to $2,000 for the purchase and installation of residential solar electric and solar water heating systems. An individual can take both a 30% credit up to the $2,000 cap for a solar electric system and a 30% credit up to a separate $2,000 cap for a solar water heating system. A 30% tax credit up to $500 per 0.5 kW is also available for fuels cells. The tax credit does not apply to solar water heaters for swimming pools or hot tubs. For most residential, grid-connected PV projects, the $2,000 maximum credit will apply since the total installed cost averages about $9,000 - $10,000 per kilowatt (before state or federal incentives).

The credit is calculated based on the individual's expenditures excluding any other government (e.g., NYSERDA) or utility incentives received. If the credit exceeds tax liability, the excess amount may be carried forward to the succeeding taxable year. Expenditures include labor costs for the onsite preparation, assembly, or original installation of the system and for piping or wiring to interconnect the system to the dwelling.

To be eligible for the credit, a system must be "placed in service" or activated between Jan. 1, 2006, and Dec. 31, 2007. If the installation is on a new home, the "placed in service" date is the date of occupancy by the homeowner. Expenditures with respect to the equipment is treated as made when the installation is completed. This provision is particularly important for expenditures made before 2006 for projects not "placed in service" until 2006. The IRS will be issuing further guidance on claiming this credit.

Solar water heating systems must be certified for performance by the Solar Rating Certification Corporation (SRCC) or a comparable entity endorsed by the government of the State in which such property is installed.

For even more detail see Energy Policy Act of 2005 (Section 1335)