Solar ERoEI Is Actually Really, Really Good

This article is part of our “CleanTechnica Answer Box” collection. For some reason, there are certain anti-cleantech talking points that get thrown around over and over that are absolutely false. We got tired of dealing with the same myths repeatedly, as we’re sure many other people have. At the suggestion of a reader, we created this CleanTechnica Answer Box resource in the same vein as Skeptical Science’s responses to global warming & climate change myths.

Myth: solar energy has low, even counterproductive, energy return on energy investment (ERoEI)

Short answer: Actually, solar energy has superb energy return on energy investment (ERoEI) — 1 to 4 years, according to the US National Renewable Energy Lab, or 1 to 2.5 years in Europe, according to the Fraunhofer Institute in Germany.

The terms “energy payback” and “energy payback period” when used to discuss solar power might be kind of confusing at first glance, but when you dig a little deeper, you get much more clarity. Energy payback refers to the amount of energy a solar power system has to make in order to equal the energy which was used to produce it. Most solar panels are made up of solar cells which are manufactured from silicon. This non-metal element must be processed in order to be usable in solar cells. The processing consumes some energy, as does the assembly of solar cells into solar panels.

Solar Energy Return On Investment — Energy Payback Period

Some critics and skeptics incorrectly say too much energy is consumed in the production of solar panels and that the panels don’t generate enough electricity during their lifetimes to make up for it.

This criticism has been proven to be false, and may be nothing more than a deliberate form of misinformation intended to persuade people who are interested in solar power to lose that interest. Too often, the critics turn out to be people who are directly or indirectly connected to fossil fuel industries like oil and gas, nuclear, or coal. They also may be politically conservative — certain highly politicized members of that group have historically opposed renewable energy to some degree.

Let’s look at what a neutral scientifically focused source, the US National Renewable Energy Lab, says about solar power and the energy payback situation: “Energy payback estimates for rooftop PV systems are 4, 3, 2, and 1 years: 4 years for systems using current multicrystalline-silicon PV modules, 3 years for current thin-film modules, 2 years for anticipated multicrystalline modules, and 1 year for anticipated thin-film modules (see Figure 1). With energy paybacks of 1 to 4 years and assumed life expectancies of 30 years, 87% to 97% of the energy that PV systems generate won’t be plagued by pollution, greenhouse gases, and depletion of resources.”

The Fraunhofer Institute in Germany published a document containing similar figures: “The Energy Payback Time of PV systems is dependent on the geographical location: PV systems in Northern Europe need around 2.5 years to balance the input energy, while PV systems in the South equal their energy input after 1.5 years and less, depending on the technology installed.” Its report also noted there was a PV system in Sicily with a payback time of about one year.

In other words, PV solar systems today easily generate enough electricity to equal the amount of energy consumed to produce them. They then go on for many years to produce clean electricity.

Financial Solar PV Payback Period

When people talk about “energy payback” or “energy payback period,” they may also be thinking about the time a solar PV power system needs to operate in order to pay for itself financially through savings on utility bills. On average, that period is about 6–8 years in the US, according to Energy Sage. 

It is only logical that a home or business owner who is considering getting such a system would want to know if it would be a sound investment. If you have a home solar power system that pays for itself in 8 years, and it produces electricity for 25, then you could say the free electricity period would be 17 years, which sounds pretty good.

Currently, no one asks, “But how long will I have free electricity?” because there is no such term “free electricity period.” However, the term “energy payback period” suggests a logic wherein one could derive this term. To be more precise, one could pose the question, “How long will I have free, clean, renewable electricity?” In the case of a 6–8 year payback period, the buyer then just needs to consider how long beyond that they will be using the solar panels. The period of free, clean electricity would be a little more than twice the payback period if they expect to use them for 25 years.

Another factor that can influence the payback time for a home solar power system is a potential increase in the home’s value. A research study found that installing a home solar system could increase the value of a home by about $15,000.

For homeowners who sold their homes after having new home solar power added, the result could be getting an extra $15,000. That money would help pay for the system, or if it had been paid off, it would be income.

A different study found that homes with solar power systems tend to sell faster, which can be more convenient depending on one’s life circumstances. (In some situations, people need to sell their homes as quickly as possible to pay for medical bills, to relocate for a new job, or for other reasons.)

Image Credit: NREL