High efficiency solar panels: what are they and do they matter?

When you’re spending $15,000–$30,000 on a solar panels for your home it’s only natural to expect high quality and performance. In this article we’ll show you how solar technology is judged and whether or not efficiency is important for your needs.

What is solar panel efficiency?

Solar panel efficiency or solar module efficiency is the percentage of light that hits the panel and is converted into electricity. Each solar panel is comprised of 60 to 96 solar cells, and it is the quality of these cells that dictates its efficiency. The efficiency rating of a solar panel is calculated by factoring in the number of solar cells, their cell efficiency, and the space between the cells on the panels.

High-efficiency solar panels are those that use less space to reach the desired power output. So if you have two solar panels with the same power output, e.g. 300 watts, the more efficient one will have a smaller footprint.

Most residential solar panels in the United States are made of crystalline silicon and have an average efficiency rating of 15%–19%.

Image source: Lafayette Edu

Does solar panel efficiency matter?

In some cases no - and in others yes.

The higher the efficiency of the panel, the higher the price. Whether paying more for more efficient panels is worth it or not depends entirely on your budget and roof space.

If you have a small roof and no budget restrictions opting for a more expensive, high-efficiency panel would work better. On the other hand, if you’re working within a budget and roof space isn’t an issue, a cheaper lower efficiency panel might work best for you.

It’s also important to remember that panels only represent about 34% of the total cost of your solar system. So although lower efficiency panels will be cheaper, opting for them might not reduce the overall solar system price by too much.

Which solar panel has the highest efficiency?

The SunPower solar panel SPR-X22-370 has an average efficiency of 22.8%, making it the most efficient commercially available panel to date. The LG High Neon R model is a close second at 21.7%.

Here are the 5 most efficient solar panel models out of those installed in the US residential solar market:

Manufacturer	Model	Rated Efficiency
Sunpower X Series	SPR-X22-370	22.8%
LG Solar	High NeON R Module	21.7%
REC Solar	REC Alpha Series 380AA	21.7%
CSUN	China Sunergy Mono CSUN410-72MH	21.2%
Solaria	PowerXT 370R-P,D 365R-PD	20.5%

Source: SolarReviews

If you’re curious, you can see the full list of most efficient solar panels on the market currently.

Panels with higher efficiency have been produced, but they aren’t available to the public yet. They are so expensive to produce they just aren’t worth it for normal residential or commercial uses.

Does solar panel temperature affect power output?

Absolutely, with all electronics, the efficiency decreases as temperatures rise. When panels are tested by their manufacturer they’re placed in a cold 5℃ (41℉) room with a very bright light being shone at them, these conditions are known as ‘Pmax.’

Since solar panels are 20℃ warmer than the ambient temperature, 25℃ is the Pmax temperature of the panels. What your panel produces at Pmax will rarely be what it produces on your roof.

The temperature coefficient of a panel shows how much output decreases for each degree over 25℃ (Pmax). Most panels have a temperature coefficient of 0.4%/℃.

The table below shows how much the output of your solar panels will decrease at different temperatures.

Temperature	50℉ (10℃)	70℉ (21.1℃)	90℉ (32.2℃)
Temp. Coefficient	0.4%/℃	0.4%/℃	0.4%/℃
Output reduction	2%	6.44%	10.88%

Higher end panels from solar panel manufacturers like Panasonic and Sunpower can have temperature coefficients of 0.28%/℃.

[Learn more: Understand and compare solar panel specifications]

Do solar panels produce more on hot days?

While heat reduces the efficiency of panels, the increase in light more than makes up for the slight efficiency loss. This is why solar panels in Arizona produce the most energy despite the warmer climate.

The map below shows the daily output in kilowatt-hours (kWh) from 1kW of installer solar, which is about 3-4 panels. The figures below are averaged over a year.

Image source: SolarReviews

Are solar panels worth it in colder climates?

Yes, states like New York and Massachusetts are two of the largest residential solar markets in the country. Even though panels produce less energy, current solar incentives make solar extremely profitable even in colder climates.

How many solar panels do I need?

The average home in America uses 28kWh of power per day. If we take southern California as an example we can divide 28 by the average production there (4.5) and work out that you need a 6.22kW system. Depending on the output of the panels 6.22kW would be 21-25 panels.

How much do solar panels cost?

Fierce competition within the industry and generous tax credits has driven the price of solar lower than ever before. An average sized solar system costs about $13,000 after the federal tax credit. Although $13,000 is a lot of money, it’s minuscule compared to the $80,000 that homeowners can save in avoided electricity bills.

For a free estimate on the installed cost of your solar power system with local incentives enter your zip code below.

What solar incentives am I eligible for?

Provided you pay income taxes you should be eligible for the federal solar tax credit. Under this incentive, you can claim 26% of your solar systems cost as a deduction to your federal income taxes (essentially a 26% discount anywhere in America). Your state government may also offer additional tax credits or rebates on top of the federal tax credit. In some cases, homeowners end up paying 50% less for their solar system!

Where can I find reliable solar companies?

You can easily compare solar companies in your area by visiting the solar companies section on Solarreviews.com. If you wish, you may also receive obligation free quotes on the size and price of your solar system with local incentives accounted for.