On Installing Solar Array and Battery (Tokyo)

[Deep Blue]

Thanks, very interesting. I know the life of solar panels is easily 15-20 years, how about the battery? Does it degrade a bit each year and in a decade it’ll be a lower capacity? Any mention of this or warranties around it?

[Bronson]

Anyone with a standalone house living in Tokyo should seriously consider installing a solar array. The city government subsidies for batteries covers 2/3 of the cost, and separate wards also tend to offer their own subsidies on top of that. There are also green subsidies like the こどもエコすまい project which offer money for eco-friendly house renovations (despite the name, you don't have to have kids?). I had a similar setup to TJKansai installed last year that cost a little less than 2.5 million yen, but after all subsidies the total cost is less than 700k, which means they pay for themselves after about 7 years. For those interested, the panels have a 25-year warranty and the battery is covered for 15 years, though will degrade to about 60% of its total capacity by that time. I don't think it's currently worth it without the subsidies, but for cheap/free electricity most of the year and the ability to run off the grid during a blackout, I think it's a pretty solid deal in Tokyo.

[RetireJapan]

the ability to run off the grid during a blackout

Is this because of the battery? When I was looking at solar a few years ago, I was told that if you were connected to the grid the panels wouldn't power the house during blackouts (other than one plug or something). Always struck me as strange, as that was one of our main reasons to get them

[Deep Blue]

Yep, and the battery won’t last for long if you need power intensive things like a/c, heating or washing machines. But to keep the fridge on and communications going (smartphone etc!) for a bit it will help.

I think the bigger reason to have a battery must be to store electricity produced when the grid doesn’t need extra power and then release it when it does? Or can the electricity in the battery only be consumed by self-use?

[Deep Blue]

Anyone with a standalone house living in Tokyo should seriously consider installing a solar array. The city government subsidies for batteries covers 2/3 of the cost, and separate wards also tend to offer their own subsidies on top of that. There are also green subsidies like the こどもエコすまい project which offer money for eco-friendly house renovations (despite the name, you don't have to have kids?). I had a similar setup to TJKansai installed last year that cost a little less than 2.5 million yen, but after all subsidies the total cost is less than 700k, which means they pay for themselves after about 7 years. For those interested, the panels have a 25-year warranty and the battery is covered for 15 years, though will degrade to about 60% of its total capacity by that time. I don't think it's currently worth it without the subsidies, but for cheap/free electricity most of the year and the ability to run off the grid during a blackout, I think it's a pretty solid deal in Tokyo.

I’m tempted. Our house is forty years old so I’ve always thought these sort of capital intensive projects don’t make financial sense but given it’s in good order and we have no intention of rebuilding maybe we should look into it.

[Moneymatters]

the ability to run off the grid during a blackout

Is this because of the battery? When I was looking at solar a few years ago, I was told that if you were connected to the grid the panels wouldn't power the house during blackouts (other than one plug or something). Always struck me as strange, as that was one of our main reasons to get them

That single socket limitation does still seem to exist for many pure solar implementations. Look into 自立運転機能
Which might require a manual switch over or additional sockets for some devices…
And even with a battery implementations can vary both on which outlets would be supported and maximum peak drain. Though many battery installers will now offer to provide power to all outlets.

The figures people are throwing around regarding degradation of panels and batteries are just estimates. The installer I’m using provided two specific examples, panels. Kyocera I think. Dropped to 80% after 26 years (not a typo). Battery(forget the brand but the technology is what matters most). Still over 80% of new after 10 years.

As for what you can power and for how long that’s just maths. The problem is you need you own data. What does your fridge need will be different from the 620L “mortician hobbiest” thing we have..).
Aircon figures are utter bullshit. Firstly because people writing these blogs think 28 degrees is livable. And secondly because each house / room will be different. I’ve measured the aircon socket in my study when it’s just ticking over and it’s about 0.3-0.5kw drain in the height of summer.(that a/c is 20 years old!)
Our bedroom should be similar but it’s 200V so I can’t measure that one. I’m setting to 25-26degs.

In summer. With 10kwh I suspect I can cover a/c in one room, fridge, led lights and charging phones outside daylight hours. Although I’m not sure I could use the same during sunlight hours whilst also replenishing the battery. But I’m not sure that’s viable anyway as there is no way we could be in the same room all day… the horrors..

[Bronson]

the ability to run off the grid during a blackout

Is this because of the battery? When I was looking at solar a few years ago, I was told that if you were connected to the grid the panels wouldn't power the house during blackouts (other than one plug or something). Always struck me as strange, as that was one of our main reasons to get them

Yes that’s what was explained to me as well. When the days are long, you can go days without connecting to the grid.

[Bronson]

I think the bigger reason to have a battery must be to store electricity produced when the grid doesn’t need extra power and then release it when it does?

Exactly. You can actually set it to various functions depending on your preference. Like if you want at least half a battery charged at all times, you can do that and then power off the grid once it dips under 50%. Or you can set it to charge only at night, if your electricity rates are cheaper then.

[Bronson]

Anyone with a standalone house living in Tokyo should seriously consider installing a solar array. The city government subsidies for batteries covers 2/3 of the cost, and separate wards also tend to offer their own subsidies on top of that. There are also green subsidies like the こどもエコすまい project which offer money for eco-friendly house renovations (despite the name, you don't have to have kids?). I had a similar setup to TJKansai installed last year that cost a little less than 2.5 million yen, but after all subsidies the total cost is less than 700k, which means they pay for themselves after about 7 years. For those interested, the panels have a 25-year warranty and the battery is covered for 15 years, though will degrade to about 60% of its total capacity by that time. I don't think it's currently worth it without the subsidies, but for cheap/free electricity most of the year and the ability to run off the grid during a blackout, I think it's a pretty solid deal in Tokyo.

I’m tempted. Our house is forty years old so I’ve always thought these sort of capital intensive projects don’t make financial sense but given it’s in good order and we have no intention of rebuilding maybe we should look into it.

One thing to keep in mind is your roof needs to be fairly new-ish, or you’ll need to replace it before the installation. I didn’t get into the details since our house is only 4 years old, but it sounded like if your roof needs to be replaced soon, then you’d be asked to do that before the installation.

[Deep Blue]

That is interesting to know thanks. I don't think we need to replace our existing roof - we had a scam company try to tell us this was needed (!) - but it's a long way outside of my competency so it is possible. I guess this would show up at the free inspection time.