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Making the most of your solar generated electricity

Posted by Chris Rudge on 23 February 2012 at 9:55 am

A lot of people ask how they can make the most of the power generated by their solar PV system. This question is especially important now the feed-in tariff (FiT) rate is (or will be) 21p as you will want to get the best from your investment.

You will receive an export payment which will be 'deemed' to be 50% of your generated power at 3.1p a unit, so it pays to use as much of your PV power as possible. Until smart meters are fitted it will not affect your export payments at all!

Most solar PV system owners soon work that it's good to run as many electrical appliances during the day as they can. You should for example use your washing machine and dishwasher during daylight, as even on a low light day the operation will be supplemented by solar power. Sunny days can probably run the whole appliance!

You could also consider changing your lifestyle a little. Use a slow cooker more than you do now, cut the grass with an electric mower (not petrol) in bright sunlight (not such a tough thing to do). There are so many other little electrical things you can use, which all add up: charging laptops, batteries & phones. Do all this in daylight if you can. Simply put: try and use as much of your power as you can during daylight.

On a slightly unrelated note, your household lights will be used mostly at night when the PV system is not generating at all, so it really does benefit you to pay a little more and install good quality low energy lamps. Most people nowadays do just this, but the real culprit I see again and again in houses and retail outlets are downlights and spotlights using 50W GU10 type lamps. Ten of these power-guzzlers will use 500W of power, or around £85 a year, even if only used for 3 hours a day.

Until recently, there have not been decent low energy replacements, being stuck with compact flourescents. However 5w warm white LED lamps have come down in cost and will provide the same light output as a 50W tungsten. Our 10 lamp power-guzzling room will now only consume 50W or £8.50 a year!

Purchase cost of these devices have fallen to around £10 each, but unlike tungsten, they have a life of around 25,000 hours and do not keep blowing filaments. They will pay for themselves in just saved power within 2 years.

One item that keeps coming up in conversation with our customers is the use of a simple timer on their immersion heater. On the surface it's a great idea to set up a timer that will switch on your hot water immersion at 11am and off again at 1pm, thus taking advantage of the midday sun. However, even if you had a 4kWp system and only used this method during spring, summer and autumn, your 3kW immersion would use more power than it saved due to weather, cloud, etc.

This midday timer setup is quite common use, and made us start thinking of a better way to achieve the same result without buying power from the grid. The resulting  auto Immersion Relay is proving a popular item we now sell. Its an ideal supplement for gas and oil users.

About the author: Chris Rudge is a qualified electrician who specialises in renewable energy.

If you have a question about anything in the above blog, please ask it in the comments section below.

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15 comments - read them below or add one


SooriComment left on: 12 March 2020 at 6:22 pm

Can I ask: im new at this.  I have 14 panels installed, i have a feed in tarrif and getvery little in comparison to what I spend. I wonder if I switched to Economy 7 meters will be spending less?

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Caitlin Moran

Caitlin MoranComment left on: 3 September 2014 at 12:55 pm

Hi @pechis

Sorry for the late reply. We recently had a similar enquiry from someone who's sytem had gone wrong, they were covered by REIGA, who were able to reimburse the cost of fixing the system. They contacted an installer near them and they were able fix it.  However, it does depend on what your REAL guarantee covers. It may be a good idea to contact them to make sure that the guarantee is still valid, as the installer has gone out of business. If it is still valid, then contact an MCS accredited installer who are happy to maintain solar pv installations and repair them, if necessary. 

I'll double check with a collegue to see if there is anything else that can be done and what you can do if you are not covered and get back to you as soon as possible.

Please let us know how you get on.

Caitlin - YouGen Team

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pechisComment left on: 28 August 2014 at 1:05 pm

My pv installer has gone bust. I have some concerns over performance and am worried about it breaking down. I have the REAL guarantee but how would i get the system checked and if necessary claim on the guarantee?

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Cathy Debenham

Cathy DebenhamComment left on: 4 March 2014 at 10:47 am

Hi Alick

The eligibility date for your solar system is the date that your FIT supplier (EDF in your case) receives your correctly completed application form with MCS certificate. You will then be paid for 20 years from that date. Given that you have sent it special delivery you should fine, as long as you haven't made any mistakes in filling in the form. 

The old fashioned meters go backwards when your panels are generating, which means that your electricity bills will be lower than they should be. It is the energy company's responsibility to change the meter and they don't generally charge to do so. I suggest that you tell them. If you don't there is a danger that you will face an estimated bill for the amount underpaid when they notice it's going backwards.

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alickComment left on: 1 March 2014 at 8:51 pm

I have just had a 3.97kw solarpv system fitted just four days ago and have heard horror stories about edf and offgem taking ages to sort the paperwork for feed in tariffs.I am hoping to get the rate set for my system before the end of march deadline.

Initially I was given to understand that this would be starting from my installation date but read something about suppliers including edf somehow claiming that people could not claim for the days of generation before they had recieved the paperwork or even later like the time when they had finally sorted out and told the customer that all was in place.These customers also said they weren't notified by edf when the paperwork had been done and had to phone in themselves to find out before their paments would be set up and start??This sounds like a minefield that I just don't wan to get into.can someone please clarify what I should do to avoid it?I posted my forms special delivery today (the post office said they wouldn't go till monday as I did it at 11.45am.)


Also I have an old style meter and my installer recomended I try to keep this as long as possible(for some reason it would be to my benefit??) and slow down the fitting of a newer meter if edf say I have to have one.Is he right?

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MulgraveComment left on: 15 September 2012 at 2:56 pm

We just got the solar immersion switch Mark II from installed. Was getting over 1500W today but immersion heater was not starting.

also installed pwer reducer tp 1.5Kw.

anybody with same system can advise?

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NECComment left on: 15 August 2012 at 11:03 am

For those that want a 1kw immersion heater there is one advertised on ebay at

Hope it helps!

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Cathy Debenham

Cathy DebenhamComment left on: 3 May 2012 at 8:34 am

Hi Jill and John

Cold, crisp winter days are perfect for generating solar electricity. Solar PV works on light, not heat, and generates better when there's lots of light, but they are still cool. See this blog by Chris Rudge for more information.

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JillComment left on: 4 April 2012 at 11:50 am

With reference to John Loder's comment, I too have noticed an interesting thing with my solar PV today.  The installed capacity is 3.57kw but at the moment according to the inverter I am currently generating  3.8kw.  I'm in the Yorkshire Dales, there's snow everywhere but the sun has just come out into a blue sky - is it something to do with the sun reflecting back off the snow? 

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John Loder

John LoderComment left on: 3 April 2012 at 5:18 pm

I am wondering if there is something hidden in all this. Here in NE Scotland we obviously are not exactly sub-tropical but we do get more sun than most people would guess. However, I have noticed that on brilliant cloudless summer days my system only runs at 80%. At first I thought 'OK it's NE Scotland' but then I discovered that the system can run at 100%. It does so when the sun comes out from behind a cloud into a bright blue sky, but only for a few minutes at most. When I asked my supplier I was told it was because the system was getting too hot and closing itself down. This seemed like nonsense to me, firstly because these systems work in really hot places and, more tellingly, because the ambient temperature seems to make no difference. Incidentally, the fan cooled inverter never gets even warm. This left me wondering if government has put pressure on installers to restrict output. Which raises the next question. Just how do installers relate with government - are they open to pressure?

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RobertPalgraveComment left on: 21 March 2012 at 8:34 am

A cautionary note about running appliances like dishwashers and washing machines on timers when you are out in order to maximise on your solar electricity.

Before I had solar PV, I used to run these appliances overnight on timers taking advantage of Economy 7 rates. One day, I was using the dishwaher at midday, and it burst into flames. If I had not been at home and been able to put out the flames, there would have been a serious house fire. If I had been asleep at night, possibly fatalities.

I now only run the dishwasher and washing machine during the day when in the house.

 Google on "dishwasher fire" tio see how often this happens - eg

there have been several product recalls in recent years to address the problem. 

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Solar Wind

Solar WindComment left on: 20 March 2012 at 7:57 pm

Hi edhill149

You are right, but only because you have an old meter that runs backwards. If you have a new meter then it is worth looking into especially if you don't have economy 7 or similar.

I have a 4kWh PV array and over the last three winter months have diverted 120kWh of surplus solar into my hot water tank. This is 23% of my total generation and I estimate that this will exceed 25% through the summer and total 1MWh for the year. However, because I have economy 7 this is only a saving of £50 at 5p per kWh. No economy 7 and it could be worth up to £150 a year.

My automatic solar diverter cost around £250 so will take five years to break even, but I think it will be worth it.

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Cathy Debenham

Cathy DebenhamComment left on: 7 March 2012 at 10:30 am

Hi edhill149

The return on investment you get depends on three elements: 

1. the generation tariff
2. the export tariff - which is deemed at half of what you generate (although it sounds as if you will be exporting much more than that).
3. savings on your electricity bill.

The third is the only one you can currently have much impact on. The system works so that if the sun's out and you are generating electricity, anything that is on in the house will pull on that first, so your bill goes down. The more you choose to put things that use lots of electricity (Hoover, washing machine, dishwasher etc) on while the sun's shining, the lower your bill will be.

You mention your meter going backwards. This means you have an old style one, and sooner or later your energy company will come and change it. In the meantime you are getting an extra bonus, but it won't go on for ever, so don't rely on it.

So it's better to use your immersion during the day if you can use the free electricity, but in winter it may be better to stick to economy 7.

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edhill149Comment left on: 6 March 2012 at 2:33 pm

First of all i am a newbie to solar microgeneration .  4 Kwp 2 string system installed 4 oct 2011 , registered on 23 oct.

According to my calculations, the perceived notion of using all available power generated , as opposed to sending power to the grid is somewhat flawed?? especially now most people have economy 7 fitted.If my calculations are wrong i hope someone will point out my errors.I believe it should all be about knowing the cost of your useage. Right to task.If i have no power drain at all from my household electricals and during the day i generate say 10 KwH then my electricity meter will rewind 10 units ; correct?? , if i use 5KwH, meter will show only 5KwH credited; ok so far; So i know my day rate tariff is close to 11 pence per KwH so if i use the power i,m being charged day rate , and losing day rate meter rewind for any sent to grid ,ie the same 11 pence per KwH.This is what is mystifying me??Why would i want my say immersion heater on and pay 11 pence per KwH when i know the night rate is only say 5 pence per KwH on econ 7.Until someone more knowledgeable than me  can convince me otherwise, i.ll continue using econ 7 for most  suitable things.  i,ve probably made a fundamental error so please, someone,  let me know.(2x 19.5 KwH, s a day this week, hoping to break 20 KwH soon)

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utility-exchangeComment left on: 23 February 2012 at 12:14 pm

Interesting article which makes me keener than ever to install solar panels!

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