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Solar Panel efficiency

There is a perfectly logical and entirely incorrect common assumption that an installation of more efficient solar panels makes more power than a less efficient one. If they are both, for example 5kW systems, then both installations will make the same power, but the more efficient one needs less roof space to do so.

The standard physical dimensions of a solar panel is 1 Metre wide x 1.7 Metres long

Within those dimensions there are panels with outputs ranging from 250W to 360W with the most common being 270W.

When solar designers are working out what will fit on your roof they may recommend you go with a high efficiency panel (which is likely to be more expensive). For example, let's say that the only good roof on your house for solar production is the North roof, but there is only space to fit 14 standard sized 1M x 1.7M panels.

If 270W panels were used you would get a 3.78kW system

If 290W panels were used you would get a 4.06kW system

If 360W panels were used, you would get a 5.04kW system

All from the same roof space.

The most space efficient panel is the SunPower X360W, closely followed by the LG NeonR

These two models are very expensive. A 5kW installation of either of these models is going to cost $3000 to $4000 more than a same sized installation with a regular Tier 1 panel. If you can fit regular panels and achieve your desired 5kW then you probably should, because you'll never recover the premium you've spent by buying these top models. However, if you can get 5kW of SunPower X or LG NeonR on your roof, and at best 4kW of something else, then the extra kW of production capability per day will definitely pay off the premium over time.

There are also physically larger, 72 cell panels, that are 1 Metre wide x 2 Metres long with typically wattages ranging from 300W to 325W. These 'monster' sized panels weighing 28kg or more, are not suitable for residential installations. Too much flex risk in moving by hand can damage the panel. They are cheaper per Watt but should be avoided unless moved by crane (as happens with commercial installs). is the web site for Good Day Mate Pty Ltd trading as SOLAR4EVER Company registered in WA on 26th October 2008 (A.C.N.133884938)

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