I recently purchased a used house with 2.1 kW (rated or nameplate capacity) of existing solar panels that were thrown in as freebies. The solar panels are 4 years old, and currently generate over their nameplate capacity (up to 2.4 kW around noon, and it’s still June) during peak sun hours.
The difference in real performance between solar panels of equal rated capacity is generally reflected in price. More expensive panels incorporate more advanced technology, with the ability to harness more solar energy when conditions are less than ideal. Such solar panels have what’s called a high capacity factor.
Rough Formula for Residential Solar Power Generation
A common formula for electricity generation for standard solar panels here in Japan is 1000 kWh per year per kW of rated capacity. This gives you an idea of what you can reasonably expect of standard solar panels, even used ones, for the purpose of calculating the benefits vs the cost. If your panels are higher quality, this number can easily be double or even more.
When checking my power conditioner settings, there was a setting that displays the total number of kWh generated since first going into use. This number was over 26,300. Given that the starting date on the FIT registration is July 1st 2012, that amounts to an average annual generation of about 6,575 kWh, or about 548 kWh/month. Now to see how these numbers fare with the accepted estimate of 1,000 kWh/year/kW.
As you can see, this is over 3 times more than the standard rating estimate. Of course, I haven’t ruled out the possibility that the solar panels were in use prior to FIT registration, but it doesn’t really make sense as the FIT incentive would have been one of the primary – if not only – reasons for most people to make this purchase.
For residential applications (under 10 kW) here in Japan, as a rule, solar power is always used first when available. This means that although it makes more financial sense to sell all your solar generated power due to the higher buyback price and buy grid-based electricity for your normal household usage, it doesn’t really work that way.
Trying to Change the Ownership Paperwork
Here’s where the complications I hinted at above come into play (in my case at least). Even though the solar panels that came with the house are high quality and in good condition, the catch is that the previous owner can’t be reached.
What this means practically, is that even though I have ownership of the house and land – and by extension the solar panels – I also technically need the previous owner’s ok to transfer the existing FIT registration to my name. I’m currently in the process of trying to find a workaround for this.
Worst-case scenario, of which there’s a small to good chance, I’ll still get to use the power that’s generated by the solar panels, but won’t get paid for the excess. And if I’m not getting paid for the excess, that means the sleaze-ball previous owner is. Obviously, I’m not gonna let this go without a fight. Fingers crossed homies.
Continued in Solar Panels and Taxes in Japan – My Personal Experience.