Short Answer: Probably Not.
Longer Answer:
Ah, the joys of STC prices! Every so often I get an email from someone who is desperately worried that their solar installer is using the STC price to rip them off.
The suspicion is usually kicked off by one of two things: [Read more…]
Here is a photo I took of a house around the corner from me.
As you can see, it has solar panels on 2 separate roof areas. In solar jargon, you would say there are 2 “strings” of solar panels.
The main string is facing North, which is the best roof orientation for solar panels. These panels should get the optimum amount of sun throughout the day.
The smaller string is facing East. These panels will get 15-20% less sunlight than the panels facing North.
Obviously the installer could not fit all the panels on the North facing roof. Fair enough.
If your home will require solar panels on multiple roof areas, which face different directions, then you should use a special type of inverter to ensure that you still get good system performance. [Read more…]
In Part #1 I went into great detail about why the “Max Power” quoted on your solar panel specification sheet and the real max power you will actually get from that panel are very different numbers. I showed you how to calculate a more accurate max power by using some little known temperature specs.
In this post I’ll go through the other important numbers that you should look at when comparing solar panels.
Discover how to read a solar panel specification
Does a solar panel specification with “Max Power” rated at, say 190W, really produce a maximum power of 190W when it is on your roof in the blazing sun?
Short Answer: Not on your nellie!
The max power rating (in Watts) that your solar panels are rated at is the figure that everyone quotes when talking about “panel size”. If the installer or salesperson talks aout a “190W or 250W panel” they are talking about the “max power” rating of the panels. This rating is based on the power output measured from that panel under “Standard Test Conditions” (STC) that, unfortunately, are a long way from “Real World Operating Conditions”.
I got this email today:
“Hi Finn,
I’ve got a quote for a 1.5kW solar system for $2500 and a 3kW system for $6000. I want 3kW. Why don’t I just buy 2 x 1.5kW systems???
Cheers, Bob”
Bloody good question Sir!
In fact I can’t believe more people don’t ask this question. But, as always, if something seems too good to be true…
In my last blog post I explained how to find an inverter’s real-world efficiency instead of relying on the inverter manufacturer’s numbers.
The CEC or European Efficiency numbers that I talked about are a much better number to use when comparing solar inverters. And for most people they will be all you need. However if you really want to understand how your solar system is going to perform then you should also look at the inverter’s “efficiency curve”.
Your inverter does not simply have one efficiency that it always operates at. The efficiency of your inverter will depend on two minor factors and one major factor.
Solar inverter efficiency is a critical specification that directly affects the efficiency of your entire solar system. It is almost always a much more important consideration than solar panel efficiency.
All the power generated by your solar panels has to go through your inverter before you can either use the power in your home or export it to the grid (and get paid) so every percent of extra efficiency that you can squeeze out of your inverter will directly improve the performance and payback of your solar system.
So do you just need to pick the inverter with the highest “efficiency” number on the specification sheet? Well I’m afraid it isn’t quite that simple. (You guessed I was gonna say that didn’t you?!) [Read more…]
Thinking of buying a solar power system to kill your electricity bill?
Then this one simple action could shave a whole kW off the size of solar system that you need to buy to get that magical zero dollar electricity bill.
Your Solar Panel Warranty and Solar Inverter Warranty have tough new minimum standards by law. Changes to the Australian Consumer Law came into effect on 1 January 2012. These are good changes which help protect you as a solar consumer from toothless warranties when buying a solar system. [Read more…]
If, like me, you get turned on by Solar Inverters, then here are three companies doing very cool stuff that I think you should look out for in 2012:
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Richard Chirgwin (RSS) (159)
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