Anyone has an idea on how to properly calculate the size of a solar panel system needed? or know of any place that would calculate this? I am looking at purchasing a new system with battery and trying to figure the size has been difficult. I aim at covering my day to day and not selling. Battery will be for emergencies.
My yearly use is 7,990 Kwh, monthly usage ranges between 1200 kwh maximum and 400 kwh minimum.
If it is worth it to know, I need 60A breakers at home as I trip the 30A ones from time to time.
5 comments
If you can figure out your internal usage relatively acurately, various Japanese sites have heat maps of Japan, I think sharp has theirs encoded with google 3d earth, that show general panel performance, and can help you decide how many panels you require. There is a site (I can’t find it in my book marks atm) that covers a wide range of solar issues in japan, including which companies have the best product at the best rate.
The unwritten rule was always that you should tend towards overestimating when calculating your max consumption and then at least double that. Most people tend to do the opposite in order to cut costs, and then they complain about how solar is useless and a waste of money.
I don’t see how the battery is “for emergencies” firstly you need to calc how much of your consumption is daytime vs night time.
Tepco will show me daily usage. So you can compare days when people were home in the day or not. But it’s obvious in summer if running 3+ split A/Cs at night. (When the sun is sleeping and the solar panels aren’t producing electricity. I’m not sure I needed to say that but the battery for emergency comment threw me..)
1,200 is a lot to cover. Probably impractical if most consumed outside daylight hours. Let’s say that’s 40kwh a day and you only need half outside daylight. That’s a 20kwh battery that would be fully depleted so you’d need a bigger one. That’s way over double what would be a large home battery.. also. You need to produce way more than 40kwh during daylight hours. So go see how many panels that would take and if you have the space.
Will you always need 1,200 max in a month. For us. One kid moving out dropped our usage by a third. Without details, I’d say look at the sweet spot for rebates and aim at a system over 6kw and battery 10-14kwh… if your insulation isn’t great look at possible rebates of inner windows.
For the panels, efficiency is affected by location, direction, angle and season. Mainly season has the most impact. FYI there isn’t a huge drop if facing west. Best bet is to get some quotes assume a bit less than their projections.
I’m still fairly stunned by the amount of anti-solar and pro-nuclear fanaticism, that I encountered in Japan. I’m really opposed to helping you as a result of this. I encountered some of the MOST vile responses I’ve ever seen on Reddit from Japan-focused Subreddits. Very cringeworthy and pathetic.
You can use https://pvwatts.nrel.gov/pvwatts.php to help calculate your system size based on your power consumption. You use this online tool with any location, worldwide. It is a little difficult to understand for laypeople but I still encourage you to plug in your numbers. You also need to know the direction your roof exposure is and also your roof pitch for the best results. It’s a completely free tool for anyone to use.
Whether or not it’s worth it would take an examination of your power bills as well to see the cost of power and of course, if you are having power outages a solar PV system with storage will help you to prevent this.
I’m still feeling quite gross and on the fence about helping after all the attacks I have had in Japan focused subs. I may delete this ASAP so copy paste it OP.
Size of installation space (home roof, shed, carport) and orientation, as well as location in Japan can all effect the system sizing. Without knowing more a 5.5kw inverter with 6-7kw of panels will cover much of your usage. Remember if you add a battery for night/clouds not emergencies you might need to go a little bigger on the system. Also if you care about return with the cost of a bettery you might never make your money back.