Starting a new category here, green living, to chronicle the installation of solar rooftop power, with the likely unique view of a foreigner in Japan who happens to be an electrical engineer and safety inspector (not for solar installations).
On 2010-12-16, we signed up for 横浜グリーンパワー Yokohama Green Power project. YGP is part of 横浜スマートシティプロジェクト Yokohama Smart City Project YSCP. Application deadline ends 2010-12-24 at our general contractor Nitten Solar.
Update 2010-12-31: YGP deadline extended to 2011-02-07 (page in Japanese).
Posted first mention of this story on GreenITers bilingual network.
weather permitting, we will put a 3kW solar system on our roof, subsidized to offset the cost of a Smart Grid HEMS Home Energy Measurement System. This will be one of 50 study projects in Tsuzuki-ku to collect 4 years worth of data by the minute to analyze energy usage patterns. Most important will be actual energy generation in this field trial, so far based on models and self-declaration by manufacturers.
HEMS usually means Home Energy Management System - ours will be from Toshiba (called "Feminity") using the HEMS data collection and transmission equipment. We have access to our data that go out to Toshiba and are shared with the City of Yokohama. We forgo the optional remote-control-everything that a HEMS makes possible.
On Saturday, the installer came to check for wiring arrangements. Cables from the roof will come down the North wall, about here.
On the 10-channel HEMS, there will be 8 channels for us to select which circuits on the breaker board we want to monitor. Smart.
Break-even: 13 years
We learned the feed-in tariff will be 48yen/kWh for 10 years. With that, we calculated break-even at about 13 years. Lucky timing, because next year the feed-in will drop to 42yen, adding two years to the payback point, and trending down.
Not so green
Solar energy is not cost-effective. Without subsidy, it could not compete. So why do we do it? Interest in experience with new technology, a bit of daytime emergency power in case the grid fails (earthquakes) and a bit of greening by offseting a small part of CO2 that is identified as a cause in climate change.
Why not all-electric?
To my current understanding, the frequently-touted combination of going solar and all-electric, "all-denka" in Japanese does not look like a good deal. The "Switch!" campaign by Tokyo Electric, for example. Here is the catch: If you have city gas, and we do, for cooking, hot water and floor heating, each additional kWh you consume by the switch to electric costs you ~24 yen, while the kWh by gas costs ~15 yen (neglecting efficiencies, needed for a full picture). Now, if you go solar and your panels produce during a sunny daytime, each additional kWh you use then costs you 48 yen, because you cannot sell it.
Good reason to cut all the standby consumption you can. A microwave with a standby of 15W due to the shiny clock display would cost you not 3150 yen per year for standby alone, but maybe close to 4000 yen if your solar panels produce during 6h of all days in a year. Not even speaking of a refrigerator, which can break-even witin 7 years if you replace a really old one.
Staying with gas
is a good choice, economically. It gives you a second energy source in case of emergency and the environmental impact appears not that different. The impact if you go all-electric and use the Tokyo-Electric "eco-cute" heat pump and storage unit can be highly discomforting. According to a licensed electrician in Tokyo, these units do not restart automatically after a power failure (e.g. a fault in the home) and you cannot press a button to boot it up. Eco-cute requires a technician to get going again. Imagine how long this may take after a wide area power failure. Resilience fail.
In winter, I hope you have backup heating, if you happen to live in a typical weakly insulated Japanese home. Getting home heat insulation right (and subsidized, I think they do with eco-points) would save more energy than all the solar panels on suitable rooftops could produce.
What sources do you use for energy and for greening calculations?