Solar Panel , calculations

mediamatt

mediamatt

mediamatt

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Joined
15 Nov 2010
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676
Hi,

Thinking of getting solar panels and wondering if im getting the maths right. If i list the items in my house that consume electric such as..

  • Fridge 334kwh
  • Oven 600kwh
  • TV 100kwh
  • Apple TV 6kwh
  • Blah Blah 100kwh

If i add them all up and it came to say 2200kwh , i would need solar panels that generated 2200w at least to power that lot without the need to pay electricity? I know i woul dneed an inverter which loses approx 10% so if i had 2500w , that would be enough wouldnt it?

Matt
 
I think that 2500kwh is the maximum it can output. I don't think that's how much it will actually produce on a daily basis, it will decrease with time and light intensity.
 
No, your also looking at it in completely the wrong way.

Solar panels are rated at KWp not what they actually reduce.

How much electricity do you use a year?
You don't need to produce the same electricity as things use. You get FIT as well as, sale any extra electricity back to the grid.

If you want to produce all you use. You need to know what your total is. Say it's 5000kwh, that equates to roughly a 4.5KWp system in south England, on south roof at optimum angle.

There's calculators you can use, type in postcode, roof direction and roof angle.
 
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Hi,

According to my annual electricity statement , last year (aug 24th 2010 to aug 23rd 2011) we used 6221kwph

So am i right in thinking on a daily basis we used 6221/365=17kwph? Is that 1700w or 17000w??

Is that about right for a 4bed house with 3 young kids and 2 adults?

It says the average is 3300kwph in the uk

Matt
 
mediamatt said:
Hi,

According to my annual electricity statement , last year (aug 24th 2010 to aug 23rd 2011) we used 6221kwph

So am i right in thinking on a daily basis we used 6221/365=17kwph? Is that 1700w or 17000w??

Matt
Click to expand...

KWH = Kilo Watt (Per) Hour. A TV doesn't use 100kwh, more like 0.1kwh. That's 2.4kw a day.

If you're using 6221kw a year, your daily average is 17kw, or 17,000 watts.
 
mediamatt said:
Hi,

According to my annual electricity statement , last year (aug 24th 2010 to aug 23rd 2011) we used 6221kwph
Click to expand...

Well your post made me look at mine for the first time in my life :D

It's says for the year 3520kwh, that's 4 bed with 3 of us and a electric oven.

Gas was 14053kwh for the year. All I really notice is the total cost of £1k :D
 
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Glaucus said:
You're very effecient. The national average is ~5000KWh
Click to expand...

Tbh it's not even something I consider either. I just turn stuff on and off as I need it. All my lights are energy saving except my kitchen which has 12 halogens.

Probably using my BBQ to roast all joints of meat saves a fair bit of electricity too :D
 
Well , im going to sell my 50" plasma and buy an led tv, going to buy an apple tv (which only uses 6wph apparantly) and just make some general changes to lessen the expense. Ive got 3 young kids and the tv is on a lot (possibly 14hrs a day sometimes , my tv uses 340wph so thats where the bloody money is going lol
 
mediamatt said:
Well , im going to sell my 50" plasma and buy an led tv, going to buy an apple tv (which only uses 6wph apparantly) and just make some general changes to lessen the expense. Ive got 3 young kids and the tv is on a lot (possibly 14hrs a day sometimes , my tv uses 340wph so thats where the bloody money is going lol
Click to expand...

340Watts is only about 8 or 9 pence but yeah that isnt cheap. That is based on 1kw/h cost of about 23pence. My current energy usage hovers around 8 or 9 pence per hour and thats for everything that is on in the house now ( Fridge, TV, computer with 2 monitors and various other items) My actually bill is a lot at the moment because we have the dryer on a lot and of course the heating is on quite a bit but it evens out over the year.

If you are looking at solar panels I think you have missed the boat since I believe the government are not now paying the nice fat feed in tarifs for any surplus electric you use. The best way to make use of solar is to have a constant high use of electric so you dont really have to `store` any of it becuase that takes more energy and isnt as cost effective.

I look after quite a large data centre and we looked at solar panels to power some of the equipment but nothing ever came of it becuase we want to get some of the money back through the feed in tarifs.
 
To provide that kind of level of input you would be looking at spending upwards of £20,000 on solar panels. The feed in tarifs were designed to offset the initial outlay of that kind of money and help to pay it back. You will currently be lucky for a setup to last longer than 15 to 20 years and at about 1k a year its really a gamble if you actually save any money or not.
 
Glaucus said:
what do you base that on.
Click to expand...

The current level of technology that is availible, the feed in tarifs were also designed to push some research into this area and the inverters and batteries that are currently used are not made to last that long. Give it a few years and the technology will have moved on a bit. There is already talk of them being able to double the output rate of certain cells within the next few years.
 
Slade2 said:
The current level of technology that is availible, the feed in tarifs were also designed to push some research into this area and the inverters and batteries that are currently used are not made to last that long. Give it a few years and the technology will have moved on a bit. There is already talk of them being able to double the output rate of certain cells within the next few years.
Click to expand...

You don't need batteries.
Most panels have a 25 0r 30year guarantee on them. Which is why I asked.
 
ok, you spend that kind of money out now and try to get them replaced under guarantee in 20 years, good luck with that. I know a lot of solar panel install companies have already gone belly up after the government stopped the feed in tarifs. I was just advising that imho its better to wait a year or two if you are thinking of spending that kind of money to see what happends with the technology.
 
ah, yes I stand corrected. They were orginally due to stop to new installations on the 12th December 2011 but it seems the government changed there minds and are just reducing the level of money you get back.

More info here: http://www.fitariffs.co.uk/FITs/regulation/review1_comprehensive/

I am only offering advice. Most small scale PV installs will generate upto about 2000 to 2500 Kwh over the course of a year as you said the national average is 5000Kwh so that would only help out with half of the cost.

One thing that really helps when looking at systems like this is to evaulate the energy use in your home before you concider systems like this. It might be that you can save a lot of money from simple things before heavily investing in systems such as this.
 
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