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How can we best use our solar generated electricity?

Posted by Cathy Debenham on 2 November 2012 at 9:34 am

Q: We have just installed PV solar panels, rated at max output of 2.25 kW. Very pleased so far (3 weeks). Careful use of daytime electricity and a woodburning stove for cooking means our energy is only costing an average of around 50p per day. (We collect waste wood to burn and we do most of our cooking on it, including hot water for drinks and washing etc). Need info about how to best utilise the solar generated electricity, preferably storing it as heat in storage heaters or as hot water. Good advice is proving hard to find, there seems to be little expertise around

A: Great to hear that you like your solar panels. How you interact with them can have a significant effect on the return that you will get from them.

The more of the solar generated electricity you can use on site, the better the return. You will get a deemed export of half of what you generate whether you export it or not. You will get just 4.5p per kWh, where you probably pay around 14-16p to import it.

So rule number one is to schedule activities that use electricity while the sun is out. These would include running a dishwasher or washing machine or doing the Hoovering.

I find it helpful to have an energy monitor, that tells me at a glance when my panels are generating more than I'm using. I use Wattson, you can read my review here, but there are others available too.

There are a variety of ways to use excess solar electricity to heat water ranging from manual, to totally automatic. The more automatic, the higher the cost. Click the link above to find out more. We will be reviewing the most popular systems on the site this month, so keep a look out in the blog if you want to read about them.

Using the electricity in storage heaters is problematic. Firstly because you need the heat in winter, when you generate significantly less heat. Secondly as your system will not generate the 3kW needed to do this. Our energy expert advises against - read why here.

If you are prepared to make a fairly hefty investment, there is a new system just launched which allows you to store excess electricity for use in the evenings. The SunBat offers enough power to cope with cooking, lighting, the TV etc.

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Comments

7 comments - read them below or add one

Cathy Debenham

Cathy DebenhamComment left on: 10 May 2013 at 10:00 am

Hi Fi 

storage is set to be the next big thing, and so you may be better off waiting a bit and seeing what comes on to the market. I have asked one of our expert bloggers to write about what's available now, so sign up to our RSS feed (or Facebook or twitter) to see when it's posted.

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fi

fiComment left on: 9 May 2013 at 11:00 pm

I am looking for a power pack that I could charge during the day, and run my TV or sewing machine or whatever off at night (maybe along with a standard lamp).(I do not have a hot water tank to heat up during the day!)

I have found a couple of items - geared very much towards jump starting vehicles - like this http://www.tantronics.co.uk/acatalog/Compact_6-in-1_Portable_Power_Pack__Portable_Power_Station_.html but wonder if there is something out there that would do the trick? I'm not too worried about unsightly - but would prefer not to be using car/vehicle battery + inverter because of the battery acid.

Any thoughts/advice gratefully received!

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Cathy Debenham

Cathy DebenhamComment left on: 3 December 2012 at 11:27 am

Hi CS

thank you for your question. First a point about your meter running backwards. This is because you have an older type of meter, and as soon as your energy company notices they will want to change it. (You may want to tell them yourself, as some contracts require you to do this, and threaten to charge you for any unpaid usage).

To explain further:

The electricity you generate is free, and any appliances you run while your solar panels are generating will be used first, then any extra needed will be bought from the grid at around 15p per kWh. When there is excess it is exported, and the energy company pays you 4.5p per kWh (this is assumed to be half of what you generate). You benefit more by not buying extra at 15p, than you do by selling excess at 4.5p.

At the moment you are getting an extra benefit, because as you export your meter goes backwards. This isn't meant to happen, and when your energy company realises how much your consumption has gone down it will almost certainly put a stop to it. It is distorting how you see the ebb and flow of electricity.

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CS

CSComment left on: 1 December 2012 at 9:21 am

I am confused by the necessity to use the electricity as it is generated for optimum returns.  During the daytime, my basic Elster solar meter clocks up the Kwh generated by my panels and (presumable at an equivalant rate) my consumption meter rolls backwards.  Why does it make any difference when I use my generated power?

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greenman

greenmanComment left on: 10 November 2012 at 6:10 pm

In case it might be useful for others....I bought a unit sold at www.totalpowershop.com.  I bought their TP-S610A starter kit (they call it a Renewable Energy Monitoring Unit or their REMU I).

It monitors how much energy my house is consuming and how much power I am getting from my solar panels or any other renewable energy source. I've set it up so it automatically switches on my immersion heater (and up to 2 other appliances) when enough surplus energy is being generated.

It is only £199. I think it will pay for itself as well, although may take a couple of years to get my money back. In the mean time it will make sure that my home is not consuming anymore power than I want to. The control unit will also record my home’s energy production and consumption and download it to a pc.

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Cathy Debenham

Cathy DebenhamComment left on: 5 November 2012 at 9:40 am

Firstly install a reducer on your immersion take taking it from 3kWh to 1.5kWh. Then install a power switch which will enable the solar power system to use the excess energy to heat the water in the tank. - comment left by Lee Chapman on LinkedIn.

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Anonymous

AnonymousComment left on: 4 November 2012 at 7:39 pm

Hi Cathy,

Please visit www.immerSUN.co.uk , I am sure you will like what you see!

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