Some Puzzles On Solar System

I must be missing something.

I'd think the best times for large users would be during the middle of the day, when the sun's highest.

I agree to best times for us being at noon.

JesseConant, correct me if I am wrong.

1. Your solar panels generate 5 kw per hour.

2. Your daily consumption is 60-65 kwh

If you are able to generate peak power for 8 hours @ 5 kwh, then you should be able to save 40 kwh per day. Your utility load should come down to 20-25 kwh. If you observe/monitor out put for a few days, you will know the best time of peak loading.

Almost correct. If you do not get a feed in tarif you can only offset what you use but you have no gains if you do not use anything. If you have a constant load of 5 KW over the day then anything towards this will save you the 25 KW you say, but if you have an irregular load you might not save nothing or not as much!

Lyn is correct that you should put load into the sunny hours.

I would go and monitor the standard load and when ever you are under 5 KW you need to switch on what ever you want to keep the gain the highest.

Keep in mind that the system won't generate 5kW all day long. It will only generate that peak around the noon hour. This can be extended by using a tracking mount.

This is correct! So this will mean that you get the maximum gain from your system when you at least use as much as you produce at the actual moment. I still would not switch on anything useless just to max out on your "gains" of course.

5 KW is somewhat high for home use. It takes some combined loads to get there. Couple of Freezers, Fridges, Server, computer, lights, a pool pump maybe.

Who needs lights over the day??? If you leave it on in the fridge will cost you dearly I think!

Jesse, looking at your OP me think that a 2 KW system is probably almost overdesigned for domestic use. 5KW without feed in tarif is a waste of money unless you can provide the basic load for it. Are you running a workshop at home with some welding equiment or drills or compressor? You need really to look at what you use over the day and which load you can shift around. Otherwise go for a smaller system.

<...5 kw per hour...> is meaningless.

<...60-65kw per day...> is meaningless.

Explain, please.

Actually, the OP meant kWh, though he wrote kw instead.

Hi Jesse, A 0.5kW system will provide power for ~6 hours per day (depending on location)

Thats 0.5kW*6hr = 3kWh each day (a typical power cost in Australia is 0.23$/hkWh saving ~ 70 cents/day.

If you're using 60kWh each day it may be better to improve your houshold efficiency by insulating, using LED lighting, changing how you heat, etc.

1. 60 to 65 kw per day is meaning less; I am assuming that 60 to 65KWH per day (or Units per day); if this correct it is too high consumption. First you need to reduce this using energy efficient products.
2. picture shown is 500W? is it 250W X2?
3. In India we get 1500 to 1700 Sun-Shine hours per year. Check with your country.
4. Battery efficiency is not more than 65%. Hence use maximum solar power for your day time daily needs as much as possible. Use this solar power to charge batteries when there is no way to utilize any more. and this will help reduce power bills. Now I think you can calculate electricity generated by PV per year.

A 5kw solar setup will deliver an average of around 20kwh per day allowing for system losses and 5.5 peak sun hours per day in NSW.

You will get a little more in summer and a little less in winter.

NSW do have a feed in tariff, it's just less than it was.

If the solar is connected to the grid via a smart meter, then what is generated will be metered and you will be credited the going rate for that energy whether it is actually returned to the grid or not.

If the solar is connected to the grid via an older style meter, then that meter will turn backwards when you are generating more than you are using, so you will save the cost of the full 20kwh but the meter will only record the difference between what comes in and what goes out.

Time of use will have no effect on your costings.

Overall, the saving should be around 20kwh per day at the going rate of say 25c/kwh or $1825 per year.

You should first check with your supply authority as some are a bit pedantic about the methods used to connect a co-generational system.

Dear friend,

in terms of the usage time, frankly speaking, there is no strictly limit. Just make sure that your battery is fully charged.

according to the power of your panel: 20*250W=5000W, and say your local max. sunshine time will be 6 hours, it will generate 5000W*6H=30000WH=30KWH. But considering the efficiency: the panel acturally generate 30kwh/1.6(coefficient of losses)=18.75kwh=18.8kwh per day.

What is your battery capacity???

By the way, haveu buy the system or not????

If you have a smart meter in Queensland (north of NSW) the smart meter records two figures

1. When solar input exceeds grid power use

2. When grid power use exceeds solar input

In Qld, a unit (1 kWh) costs say 20 cents, and a unit of solar power creates a credit of 45 cents (thanks to earlier governments before the last lot of elections).

If you consume power before sunup and after sundown, all solar power goes to the grid to give you all those lovely credits.

If you consume lots of power in the middle of the day, your solar will be consumed first, then grid power, if you don't have enough solar. So you then lose all those lovely solar credits.

One kilowatt is a measure of power. One kiloWatthour is a measure of energy (power * time).

One kWh is one kW consumed continuously for 3600 seconds. The energy consumed in one hour is therefore 3,600,000 Watt-seconds or Joules ie 3.6 MegaJoules, a lot of energy for 20 cents.

You might like to compare that with the cost of petrol (gas). One litre of petrol has about 36 MJ of energy, 164MJ per Imp Gal, 131 MJ per US Gal (approx).

In Qld, petrol is about $1.36 per litre, ie 13.6 cents per 3.6 MJ, so stop complaining out there, even if you are only getting the use of about 20% of that fuel, with the rest going in heating water, the exhaust pipe, the transmission, and the surrounding air.

I'm not going to take 2 hours giving you a solar tutorial but I will suggest you do more homework than you have before you spend a dime.if you really like the idea of solar you have to understand the importance of the batteries that STORE the energy you want to harvest, I looked at that site and the info on the batteries was beyond weak.the batteries are the heart of the system, NO the little panels shown, good luck and study up before spending your money or you'll be spending plenty more sooner rather than later