Sort by ROI / Payback / Financial Benefit · Sort by Environmental / Carbon Footprint

SUR Product Comparison Chart

Below is a comprehensive listing of Solar Electric Photovoltaic PV, Wind Electric, Solar Hot Air, and Solar Hot Water products and notes that will help you find the product that best meets your needs. Read more about Incentives.

Technology Type	Carried by SUR Energy	ROI / Payback / Financial Benefit Learn More	Environmental / Carbon Footprint Learn More	Backup Power Learn More	Economies of Scale Learn More

Solar Electric					Back to top
Technology Type	SUR?	Financial Benefit	Carbon Footprint	Backup Power	Economies of Scale
Solar Electric Photovoltaic "PV" Grid-tied without batteries, <10kW (about 900 to 1800 square feet, typical residential 2-3kW)	X	MEDIUM to POOR Learn More	Carbon footprint better than a hybrid car Learn More	NONE	POOR
Solar Electric Photovoltaic "PV" Grid-tied without batteries, >10kW (about 900 to 1800 square feet)	X	Up to about $100,000 payback improves with size then tapers off	Compared to other RE technologies PV is middle of the road.	NONE	POOR
Solar Electric Photovoltaic "PV" Grid-tied with batteries	X	Payback is not as good as most other choices	Medium per dollar carbon savings. Learn More	YES	POOR
Solar Electric "Off Grid" (no utility connection) with batteries	X	If savings on utlity interconnect is significant enough, payback improves. Learn More	EXCELLENT (depending on supplimental generator/fuel)	YES (in Michigan off grid systems require both solar and wind)	POOR (if entire system grows, including batteries); GOOD (if only PV grows)
Solar Electric with shade trees	X	Shade greatly reduces PV performance. We measure shade on site visits. Learn More	Expensive technology without fuel Learn More	Much Less	N/A

Wind Electric					Back to top
Technology Type	SUR?	Financial Benefit	Carbon Footprint	Backup Power	Economies of Scale
Wind Electric Grid-tied without batteries - class 2 winds, <30' diameter	X	MEDIUM to POOR Learn More	Middle of the road Learn More	NONE	EXCELLENT (expense rises linearly and production exponentially)
Wind Electric Grid-tied without batteries - class 3 or better winds, <30' diameter	X	All of the benefits of wind power increase with FAST winds Learn More	GOOD winds make for lots of clean energy	NONE	EXCELLENT
Wind Electric Grid-tied without batteries - class 2 winds, >30' diameter	X	MEDIOCRE	NOT BAD	NONE	EXCELLENT
Wind Electric Grid-tied without batteries - class 3 or better winds, >30' diameter	X	EXCELLENT	TOPS	NONE	EXCELLENT
Wind Electric Grid-tied with batteries	X	Backup power adds expense Learn More	Complexity adds materials but not energy production	YES (systems with batteries have backup power capabilities)	POOR (if entire system grows, including batteries); GOOD (if only turbine grows)
Wind Electric "Off Grid" with batteries	X	Saving thousands on utlity interconnect helps payback	Improved investment if savings on utlity interconnect is significant enough	YES (in Michigan off grid systems require both solar and wind)	N/A
Wind Electric Systems: Utility Scale	NO	TOP INVESTMENT ON PAGE (assumes good winds)	Excellent way to spend embodied energy	NO (almost never have batteries or stored power)	N/A
Vertical axis wind turbines or turbines with high solidity	NEVER WILL (high solidity)	Negative benefit for high solidity, maybe for low solidity vertical Learn More	Negative benefit for high solidity, could get something out of a good vertical	NONE (no payback because they work poorly - don't pay more than $10)	TERRIBLE (high solidity)

Solar Hot Water					Back to top
Technology Type	SUR?	Financial Benefit	Carbon Footprint	Backup Power	Economies of Scale
Solar Hot Water with good load matching	X	Best available for most residential situations (gov't incentives being equal), especially non-nat gas water heaters	Great benefit for gas; Even better if the hot water heater is electric	Can use hot water system with solar electric pump for off grid house	GOOD
Solar Hot Water with small loads (not much hot water is used)	Standard drainback	Investing in capacity without load	OK (consider other options)	N/A	BAD
Solar Hot Water with heat for house	X	Payback for intial investment not as good as solar hot water	Decent environmental benefits but not as good as others	NO (Could be contrived but typically no)	BAD (Rule of thumb: not >70% of heat)
Solar Hot Water with shade	If not TOO much	Could be OK if shade is minimal. Not as devistating as for PV.	Decent benefit if the shade is not too extensive	N/A	Can oversize a drainback to make up for shade

Solar Hot Air					Back to top
Technology Type	SUR?	Financial Benefit	Carbon Footprint	Backup Power	Economies of Scale
Solar Hot Air to heat house	Not currently	POOR payback unless VERY inexpensive	Some benefit but better options available for most	Fan can run on PV	No expertise here
Solar Hot Air for heat and hot water	Not currently	We prefer standard solar hot water for this. Learn More	Could be OK if system works well, good if replacing electricity	Could run fans and pumps with PV	Not sure

Each of the technologies mentioned in the chart has a focused write-up elsewhere on this website. The information below pertains to how each of the technologies compares one to the other, and why.

Return on Investment/Payback/Financial Benefit

PV Payback

Wind Power Payback

Solar Hot Water Payback

Environmental / Carbon Footprint

Economies of Scale

Return on Investment/Payback/Financial Benefit

Back to list

The idea of payback is to answer the question how long will it take in energy savings to recoup my cost of installing one of these systems. This is referred to as simple payback. Many installers (the more honest ones) hate to address this issue directly but we feel it is important to attempt. In order to be accurate one needs a fully functional crystal ball that can predict the future. Payback is fully dependent on how the inflation of energy costs will compare to overall inflation and the future value of todays dollars. Even though we are not able to predict this with that sort of accuracy, we can relay the information we have heard that we feel is the most reliable. Also, please note that payback can change by orders of magnitude with changing government and utility regulations and incentives.

It has been our experience that payback is the thing that seems most important to most consumers. When buying clothes and cars most people get as expensive a product as they can afford regardless of value. When it comes to energy, most Americans as individuals and collectively often go for the lowest cost and, we feel, lowest value. These tides are beginning to change. SUR Energy as well as many other fine installers and manufacturers are doing all we can to help the payback situation.

As far as individual technologies there are many things that interact to affect the payback situation. We have taken the most important ones and made them a part of the divisions of the technologies in the column on the left in the product comparison chart above.

PV Payback

Back to list

For solar electric if we calculate the energy production over time it appears that the system will cost enough that the recouping of costs will take longer than the equipment is likely to last. The analyst we trust the most divides the time of simple payback by about 3 when he moves from simple payback to the analysis that includes inflation. If the government then pays for 30% this time frame is further reduced by the same amount of time. Now it is creeping down to below 20 years. The systems are likely to last much longer than this. This payback is probably best case without more help from the government or extreme electricity price increases and general inflation not rising as much. PV payback gets a little help from economies of scale as the installed cost per watt drops fast but then tapers off. This will likely be the case until the cost of the PV material itself is lower.

The addition of batteries to a system tends to hurt the payback rather than help it. If someone has extreme time of day use differences in cost then batteries might help, but this is unusual. Having the batteries in the circuit makes the system about 3-5% less efficient than the straight Grid-tied-without-batteries counterpart and the batteries and associated complexity add greatly to the cost. Therefore, if payback is more important than backup power we recommend straight grid-tied systems for wind and solar electric. For other buyers, the batteries are well worth the expense and lost power.

Wind Power Payback

Back to list

Wind power payback runs the gamut from excellent to terrible. The most important single variable is wind speed. If someone has a good site they can make a lot of power and get a good return. If the winds are not above a class two they probably will see little electricity from the turbine. Many turbine manufacturers brag about a low cut-in speed. One turbine begins to generate electricity in a four mile per hour wind while another doesn't start until the wind blows at eight miles per hour. We don't feel this is a good criteria for selecting the best turbine. There is almost no energy in a 4 mph wind and you cant squeeze water from a stone. Its fine to generate at lower speeds but turbine design should focus on the speeds at which the highest energy density occurs (around 16 mph for much of Michigan and other areas with a 12 mph average wind speed).

Wind turbine payback is also affected by economies of scale.

Solar Hot Water Payback

Back to list

Payback for solar hot water without unequal government incentives tends to be the best for most Michigan renewable energy customers. The collection of heat is done in a simple way with highly efficient collectors. Compared to the other technologies they do well because they collect energy rather than convert it. For this reason they avoid inefficiencies that are inescapable with the converting type technologies. Payback on these systems also depends on what type of conventional fuel is used to heat the water. If electricity or propane are used, it is probably just under 10 years without much help from the government (less for propane). If the government pays 30% you can take off the same percent for the time to break-even. Also, one strike against solar hot water systems compared to grid-tied electric systems is that in order to be a good investment energy generation has to match loads well. In the case of grid-tied equipment the grid itself is a huge load so all energy generated and making it past efficiency losses is used.

Environmental/ Carbon Footprint

Back to list

View "A Convenient SUR Truth" Slideshow
We believe that carbon footprint and environmental benefit do not coincide one to one with other factors such as payback. The biggest difference is that much of the heat we use comes from natural gas, which is a much cleaner fuel than the coal burned for a vast majority of our electricity. Therefore, offsetting a kilowatt hour of heat in a hot water system is offsetting less carbon than that offset by generating a kilowatt with PV or windpower. When compared dollar per dollar we usually consider the three technologies pretty close for carbon offset.

Another detail we look at to help people make informed decisions about carbon reduction is their habits and usage. If we come to a homeowner(s) that is doing a lot of water conservation and doesn't use much hot water, putting in a solar hot water system for them won't offset much carbon emission. On the other hand, if they have the opportunity to add more money to the budget and get a PV or wind system they are likely to, dollar for dollar, offset more carbon. Even though the expense may be double the cost of a solar hot water system the equal portion of the investment will be much more effective at achieving their goal of a smaller carbon footprint.

Many environmentalists worry about the use of lead-acid batteries and their effect on the environment. We like to remind folks that batteries are about 99% recycled. The real harm they do with carbon footprint is to divert funds away from generation. If you can purchase more solar electric panels or a bigger wind turbine for not having purchased the batteries then your carbon footprint is that much smaller. In some cases batteries and the associated hardware may add 50% to the cost of the system.

Economies of Scale

Back to list

Wind power beats them all on this factor. As mentioned above the limiting factor for PV is the cost of the photovoltaic material itself. It has a floor for cost that currently is hit pretty quickly as the system size grows. Labor and other balance of system costs go down in a fashion more like other products, but the PV just costs too much to make.

Solar hot water systems are load matching so the size is typically limited by the typical summer heat load. Otherwise, economies of scale should be quite good.

Wind power has a special advantage that is not shared by any other technology. Cost of manufacturing the turbines tends to go up in a linear fashion based on the weight of the equipment. This is a little simplistic but it is true in a general sense. The amount of energy generated by the turbine goes up exponentially based on the area of the rotor, which follows the formula of pi r squared. r squared means you multiply the length of one of the blades in to the energy formula twice. For example, when a turbine blade goes from being 9 in diameter to about 10 in diameter the area of the rotor doubles, but the weight of the turbine has changed very little and doesn't cost anywhere near twice as much to manufacture. This is one of the reasons that utility scale wind power is becoming so widely used. We have been able to make an old technology bigger.

The other factor is height. As you move the turbine higher and higher into the air the winds tend to blow faster and faster depending on topology and turbulence in the ground and trees. Taller towers is the other reason large scale wind turbines are able to compete effectively with fossil fuel generators.