My 40 solar panels lifetime production after 21 months

2 Responses

  1. NoseyNick says:

    When it comes to AC power, there are subtle differences between Volt-Amps, and Watts. The difference is phase-related – what parts of the AC cycle have the volts, and what parts have the amps. The ratio between the two is called Power Factor. A purely resistive load (heaters, most non-CFL lights) will have a 1:1 Power Factor, so VA and W are actually the same. Inductive or capacitative loads (CFLs, motors, transformers, TVs, computers, wall-warts, etc, almost everything EXCEPT heaters/lights) will usually be drawing the most current on a part of the cycle that does NOT have the most voltage, and they end up with a lower power factor, EG they might be using 0.7 kW but 1 KVA for a PF of 0.7. To add to the confusion, various bits of equipment will often measure VA whilst claiming to measure W, or vice-versa, or using the wrong units and thus implying they are measuring the other.

    You can ALMOST guarantee your power company is measuring kW, not VA, which actually works to your advantage if you’re a crappy-PF consumer, but not if you’re a producer, where you really need the PF to be as close to 1:1 as possible.

    I don’t know if your panels are ACTUALLY measuring VA or W, nor if they are doing so before or after the inverters, but a 0.94 PF, and/or a 94% efficiency in the inverters would both be pretty good. Energy Star ratings typically require >0.7PF, some better ratings require >0.9, pretty much the best I’ve seen on any equipment is 0.97.

    I guess the all-important question… The panels have earned you (back-of-envelope) $4000/yr? What did they cost to install, and when do you hit the break-even point? Also, instead of buying+installing the panels, if you had put the money in high-interest savings, you’d have MORE money now. At what point do you break even against THAT and start earning more money than the equivalent savings would have done?

  1. March 30, 2016

    […] If you want more information on my setup, please refer to these articles 40 solar panels + 1 Volt and My 40 solar panels lifetime production after 21 months. […]

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