Sunday, November 04, 2007

Another Renewable Energy Myth

I’ve heard it said that it takes more energy to create a solar panel than the panel will produce in its lifetime. That’s absurd! Here are some facts:

A 100 watt solar panel can produce about 400-watt hours on a sunny day.

In one year, that single panel can produce about 146 killowatt hours.

The life expectancy of a solar panel is more than 20 years. In 20 years, that single panel can produce almost 3 thousand kilowatt hours of electricity, enough to prevent 6,600 pounds of CO2 from entering the atmosphere. Source: National Renewable Energy Labs (NREL). Keep in mind however that these figures are for a solar panel that is in service everyday, used to its capacity. An underused panel, one on an RV that is only used a few weeks each year for example, will not measure up over its lifetime.

And, for the benefit of anyone still skeptical, consider this:

It’s better to use fossil fuel to manufacture a solar panel than to just burn it, and still have the problem.



Anonymous said...

Great post. Your were very conservative on how much the panel could produce in a day. Some area have as much as 7 peak sun hours nearly doubling the production of the panel. The biggest problem with solar has been the expense. One company is trying to change that. I have written about the concept extensively in my blog. Look at this new idea of putting solar on your home with no system purchase required at This concept is already done commercially. Can it be done with the residential market. Take a look and decide for yourself. Feel free to leave comments.

Solar John said...

Thanks raz,

I guess I was being a little conservative in my consideration of average daily production. It's also likely that a panel will last more than 20 years.

For some reason, there are those who have nothing good to say about pv. I suspect that these people are stakeholders in oil or coal, or in some area of internal combustion engines, cars most likely.


Ranjit said...

Hi John,
I am from Shillong/Meghalaya/India, this area has about 7 hrs of good sunlight on an average.. most of the year around. But the concept of green energy or the fact that there are so many districts which has power cuts during the summer season has not yet made ppl concious of the need to have atleast some independent means to harness this almost free power. the govt is some cases is giving subsidy to install solar equipment but to no avail. I am more of an enthusiat in this field. I have a small solar panel and do experiment on solar energy. Mostly i am working on white leds etc. At present my needs are emergency lighting than full system. And hv learnt tremendously from my experiments. Also due to the proximity to china.. lots of white lED lamps are available. Your article has made good reading and i learnt a lot. Thanks
Ranjit Das

lee said...

The case against PV was easy to make with solid facts about 10 years ago. Equally solid facts show modern systems do indeed require 6-8 years to pay themselves back in energy, and I think most people would view this as reasonable. Unfortunately, many factors conspire to make the 20 year lifespan doubtful. It still has a net positive effect on energy output alone.

Raz said...


The 6-8 years for payback assumes that you are going to pay cash for the panels. If you finance then you have to calculate the interest as part of the expense making the payback over 20 years.

Also it depends on two other major things.

1. the utility prices in the area of installation. If you are currently paying 20 cents per KW you will have a much shorter payback than if you pay 10 cents per kw.

2. Number of peak sun hours. Some areas have only 3 peak sun hours while others have nearly 7 hours again making a difference.

For you to say that PV will not last 20 years is silly. Systems that have been in place for 25 years have lost only 20% efficiency, No one knows how long they will last as none have worn out. You may have been thinking about the inverter which does have a 10-20 year life span.

At any rate solar may soon be affordable. 2 ways are on the horizon that may bring solar mainstream. One is thin film and the other is the Citizenre rental program. I write about the secound extensively in my blog at