# Solar panels on the window

I got these solar panels that claim to produce 1W energy with 6V.

Just out of curiosity how much energy might I be able to generate with these?

I live in Finland and in Helsinki there is 1050 sunny hours a year in average. (according to this data: http://ilmatieteenlaitos.fi/kesatilastot)

Lets say I only include in the calculations those hours where sun’s altitude is more than 5 degrees to get into more realistic hours.

So I need to do a bit of calculation: how many hours sun is above 5 degrees?

I wont go into details here now but this is what I got with a little help of python pysolar module.

When latitude and longitude is   60.2347 and 25.08565,  sun is up 4482 hours a year (every day sunrise to sun set times summed ).

Sunny percentage is thus 23.4 %

Sun is up more than 5 degrees 3796 hours a year.

23.4 % of that gives 890 hours

I now have 5 of these panels so if my calculations are correct it could be thus possible to get 890 * 5 = 4451 Wh of energy from these in a year.

My energy company estimates I spend more than 410 times that in year.

One of these panels is 6 x 11 cm

It means I would have to have 5 * 0.06 * 0.11 * 410 = 13,5 m2 of these panels and it would cost almost 2500 euros.
Actually it is not that bad,  in about 10 years it would pay itself back, roughly.

So here is a start with a design to set these up on my window: