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

SUR Energy - 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.



Solar Electric					Back to top
Technology Type	SUR Energy Installs	Financial Benefit	Reduction of Carbon Footprint	Backup Power	Economies of Scale
Solar Electric PV Grid-tied without batteries, smaller then 10kW; typical residential size 4-6kW)	X	Medium to Good Learn More	Carbon footprint improvement better than a hybrid car Learn More	None	Medium
Solar Electric PV Grid-tied without batteries, greater than 10kW	X	Up to about 20kW payback improves with size then increases more slowly	Compared to other RE technologies PV is middle of the road.	None	Medium
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 (for remote locations such as cabins), substantial savings Learn More	Excellent (depending on supplemental generator/fuel)	Yes (in Michigan off grid systems require both solar and wind for year round power)	Poor (if entire system expanded, including batteries); Good (if only PV grows)
Solar Electric with shade trees	X	Shade greatly reduces PV performance; we measure shade on initial site visits Learn More	Expensive technology without fuel Learn More	None	N/A

Wind Electric					Back to top
Technology Type	SUR Energy Installs	Financial Benefit	Reduction of Carbon Footprint	Backup Power	Economies of Scale
Wind Electric Grid-tied without batteries - class 2 winds, less than 30' diameter	X	Poor to Medium 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, less than 30' diameter	X	All of the benefits of wind power increase with FAST winds Learn More	Good wind make for lots of clean energy	None	Excellent
Wind Electric Grid-tied without batteries - class 2 winds, greater than 30' diameter	X	Mediocre	Better	None	Excellent
Wind Electric Grid-tied without batteries - class 3 or better winds, greater than 30' diameter	X	Excellent	Best- Highest reduction per $ spent	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 expanded , including batteries); Good (if only larger turbine installed)
Wind Electric "Off Grid" with batteries	X	Saving thousands on utility interconnect helps payback at remote sites such as cabins	Improved investment if savings on utility interconnect is significant enough	Yes (in Michigan off grid systems require both solar and wind for year round power)	N/A
Wind Electric Systems: Utility Scale	No	Top investment- all renewable technologies (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	Terrible (for high solidity)

Solar Hot Water					Back to top
Technology Type	SUR Energy Installs	Financial Benefit	Reduction of Carbon Footprint	Backup Power	Economies of Scale
Solar Hot Water with good load matching	X	Excellent for many residential locations- especially with non-natural gas water heaters	Great benefit for natural gas; Even better if the hot water heater is electric/propane	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)	X	Investing in capacity without load	Ok (consider PV if this is a priority)	N/A	Poor
Solar Hot Water with heat for house	X	Payback for initial investment not as good as solar hot water	Decent environmental benefits but not as good as others	No	Poor (Rule of thumb: not less than 70% of heat)
Solar Hot Water with shade	If not too much	Could be Ok if shade is minimal. Not as detrimental 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 Energy Installs	Financial Benefit	Reduction of Carbon Footprint	Backup Power	Economies of Scale
Solar Hot Air to heat house	No	Poor payback unless very inexpensive	Some benefit but better options available for most	N/A	unknown
Solar Hot Air for heat and hot water	No	We prefer standard solar hot water for this. Learn More	Could be OK if system works well, good if replacing electric hot water heater	N/A	unknown

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.

The Financials of Renewable Energy

PV Payback

Wind Power Payback

Solar Hot Water Payback

Environmental / Carbon Footprint

Economies of Scale

The Financials of Renewable Energy

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Simple Payback- "The length of time it takes to recover the costs of an investment." (Investopedia)

We offer to help our customers understand how long it will take for their renewable energy system to pay itself off and what rate of return on the investment they will receive over the life of the system. Using today's numbers keeps the calculations conservative (more on this in the next paragraph). Every proposal we do here at SUR Energy comes with a payback analysis of that particular system and takes into account site specific variables such as shading, site elevation, roof pitch, equipment efficiencies, etc.

Simple payback does not take into account rising energy costs and other variables such as environmental regulations. Payback depends partially on how increasing energy costs will compare to overall inflation; for example, if electricity rates increase faster then income increases, then a solar array will pay itself off faster then originally calculated. If past energy costs and the rate at which they have increased is projected into the future and used as a prediction tool, a more educated decision can be made. We include energy inflation rates with every one of our payback anaylsis. Please note that payback can change by orders of magnitude with changing government and utility regulations, rules, and incentives, as well as from changing (almost always decreasing) renewable energy equipment and installation costs.

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

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For solar electric (PV) taking into account energy production over time most systems will pay themselves off in 9-17 years with the 30% Federal tax break (expires in 2016) and selling Solar Renewable Energy Credits into the marketplace. The systems we install will last much longer then this; we are currently installing solar panels (modules) that have a 30 year performance warranty. PV payback also gets help from economies of scale as the installed cost per Watt drops fast as system size increases, then tapers off with larger arrays over 100kW.

The addition of batteries to a system extends the payback time significantly, but offers backup power during outages. Having the batteries in the circuit makes the system about 3-5% less efficient then its straight grid-tied without batteries PV counterpart, and the batteries and associated complexity of installation add greatly to the cost (usually double the cost of the installation). Therefore, if payback is more important then backup power we recommend straight grid-tied systems for wind and solar electric. For other buyers, the batteries are well worth the expense and slight loss in efficiency.

Wind Power Payback

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Wind power payback varies considerably. The most important single variable is average annual wind speed at the top of the turbine tower. If someone has a good site they can generate lots of energy and get a good financial return. However, if the winds are slower, such as a "Class 1" or "Class 2" as is a good portion of Michigan they will see little electricity from the turbine and 40 year + paybacks.

If a well designed wind turbine is put on a 100 foot tall tower in mid Class 3 winds then payback periods are going to be in the 20 year range for 10kW turbines, and in the 35 year range for smaller 2.5kW turbines. This is highly dependent on the foundation needed, tower height and type, etc. etc.

Wind turbine payback is also affected by economies of scale.

Solar Hot Water Payback

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The shortest payback for any renewable energy system in southern Michigan is with a solar hot water system. Systems with a good non-shaded site will pay themselves off in 6-10 years with the current Federal tax credit (ends Dec 31, 2016). The payback is even faster if the home has a electric or propane fired hot water heater.

Heat is transferred directly from the suns energy by directly warming the fluid (a water/antifreeze mix) through highly efficient roof or ground mounted collectors. Compared to other renewable energy technologies the collectors do well because they gather energy rather then convert it from one form to another. For this reason they avoid inefficiencies that are inescapable with solar electric and wind which have energy conversion losses (the motion of the wind to a rotary shaft to a generator to a inverter, for example).

One drawback of solar hot water systems compared to grid-tied solar electric systems is that in order to be a good investment, energy generation has to match loads well. What this means is that if a large solar hot water system is installed and only a small amount of hot water is used daily, then the excess gathered energy is lost. In the case of grid tied solar or wind the electrical grid itself absorbs any excess generated energy (and the owner is compensated for the sold electricity via Netmetering) and none is lost.

Environmental/ Carbon Footprint

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View "A Convenient SUR Truth" Slideshow
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 to generate the 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 a property owner 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 investment will be much more than twice as effective at achieving their goal of a smaller carbon footprint.

A note on batteries used for renewable energy: Many environmentalists worry about the use of lead-acid batteries and their effect on the environment. We like to remind folks that the large batteries used for renewable energy systems are about 99% recycled at the end of their life. 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% or more to the cost of the system.

Economies of Scale

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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.