Is solar efficient enough?


I recently overheard a conversation that made me think. A man, who was clearly respected by his friends as someone knowledgeable, commented that solar wasn’t ready for prime time because it isn’t efficient enough. But is this true?

The simple answer is “no.” Solar is plenty efficient. The solar electric panels that go on your roof are 15%-20% efficient. Solar hot water systems are about three times more efficient since they heat water directly. So the most intelligent system consists of a couple of solar hot water panels and a roof full of photovoltaic (electric) panels.

But still, you might be waiting for systems to get much more efficient. After all, semiconductors get faster and cheaper every year. If you did this, you’d be making  a mistake.

Lots of research has been going into photovoltaic panels for decades, and they’ve barely cracked 20% efficiency for conventional flat panels. Another blogger has gone through the physics of it in this article. The short of it is that current solar panels are more than efficient enough for most homes. Moreover, don’t expect any big breakthroughs.

Investing in solar

The naysayers go on to complain about the payback “I can’t wait 10 years, I’m going to wait until the prices come down enough to pay it off in 5 years!” But this too is misguided. Do you have any money in the bank or in CD’s? What are you getting for that? 1%? Maybe 2% if you’re lucky? A ten year payback for solar is a guaranteed 10% return on the investment – that’s better than just about anything out there. To me, it’s a no-brainer – if you have an appropriate location, you should invest in solar panels for your home or business buildings.

The other advantage of solar – distributed power

Most of us don’t consider the broader implications of installing photovoltaics on our homes. We’re just trying to reduce our electric bills. But we’re really creating miniature power plants when we install these panels. Every home with solar panels is helping to distribute power generation, reducing the loads on power plants, which helps all of us. Consider this – the power company has to built massive extra power capacity to satisfy the extra load caused by all those air conditioners turning on in mid afternoon. These plants drive up the cost of electricity and cause more pollution. But when people install solar electric tied to the electric grid, they’re offsetting much of the load caused by the air conditioner. This power is also more reliable and efficient because it’s smaller and more distributed. Every bit of power you put onto the grid helps to power your neighbors. And if one of these mini-power plants malfunctions, it’s no big deal.

It’s not a cure-all

Solar electric has plenty of things going for it, but you always have to consider your consumption. Even with solar, you’re better off conserving energy. Use more efficient light bulbs and appliances. Insulate your home better. Open windows to take advantage of natural breezes. Solar is a single component of a bigger conservation picture. In fact, you’re best off starting with conservation. By reducing your home’s load through efficiency, you’re much more likely to come close to supplying all your electric needs using solar. Without efficiency, you’ll be lucky to cut your electric bills in half, even with a large solar array. So start with efficiency. Your home will be more comfortable and the efficiency will pay of even if you don’t install solar electric.

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3 thoughts on “Is solar efficient enough?

  1. The whole “not efficient enough” is kind of odd. If my boiler was only 20% efficient then clearly it’s not efficient enough, because the 80% waste is doing active harm.

    Solar, on the other hand, is capturing 20% of sunlight which, if not captured, is … sunlight. Pulling in 20% of a massive, clean, free resource is not bad.

    You can do the math if you want on payback, costs, embedded energy, and all that, but focusing on that 20% number is missing the point, IMHO.

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