solar novice any advice welcome

Hi I am having solar panels fitted next week. I know little about this and despite reading up for hours am a bit out of my depth with all the figures. I am having 16 panels, told this is the max you can have, and my roof is 5 degrees off south.

I currently have full gas central heating/water, gas hob, electric oven. I have been advised to have large appliances staggered throughout the day with timers, not have both ovens on at the same time, and replace bulbs with leds, (something we have already been doing).

I am going to replace my towel rads with plug in electric ones, and wondered if there is any way to utilise the free daytime electric for night time heating, similar to the old night storage heaters?

Also what are the best electric heaters to use during the daytime? I have to heat the living room and kitchen during the day as I work from home.

Any other tips would be very welcome. Thank you.
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  • EricMearsEricMears Forumite
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    vix2000 wrote: »
    Hi I am having solar panels fitted next week. I know little about this and despite reading up for hours am a bit out of my depth with all the figures. I am having 16 panels, told this is the max you can have, and my roof is 5 degrees off south.

    I currently have full gas central heating/water, gas hob, electric oven. I have been advised to have large appliances staggered throughout the day with timers, not have both ovens on at the same time, and replace bulbs with leds, (something we have already been doing).

    I am going to replace my towel rads with plug in electric ones, and wondered if there is any way to utilise the free daytime electric for night time heating, similar to the old night storage heaters?

    Also what are the best electric heaters to use during the daytime? I have to heat the living room and kitchen during the day as I work from home.

    Any other tips would be very welcome. Thank you.


    16 (x 250 W each ?) certainly isn't the "max you can have" - unless of course they meant that was all you had room for on the roof. 4kWp is the maximum output to qualify for the highest rate of FIT payment but the second highest rate isn't a great deal less so if you have room you might consider fitting more. 4kWp is already slightly above the threshold for which you need approval from the distribution network operator and you'd certainly need their approval before fitting any more but it's unlikely to be refused.


    Absolutely don't run major appliances off timers ! That's almost guaranteed to have your washing machine coming on just as a large cloud hovers overhead :D Since you're at home during the day, stick with the more reliable system of looking out the window occasionally (or better still get some sort of output indication) and switching major appliances on when you know there's enough power for them.


    No reason at all why you couldn't run storage heaters off excess solar power. The rest of the country are scrapping them left right & centre so second hand ones should be pretty cheap. Or of course you could do as many members here have done and divert excess solar power to an immersion heater.
    NE Derbyshire.
    4kWp S Facing 17.5deg slope (dormer roof).
    BEV : Nissan Leaf e+
  • EctophileEctophile Forumite
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    It's worth bearing in mind that the output of the solar panels depends a lot on what the weather's doing.

    My rough rule-of-thumb is:
    • If it's sunny, and the sun is shining on the panels, then you'll be generating close to the maximum.
    • If it's a bit cloudy, it will be nearer 10% of the maximum.
    • If it's heavy cloud, it will be nearer 1% of the maximum.
    • If it's really dense cloud or fog, assume no generation at all.
    Notice the huge drop-off in generation a bit of cloud can do.


    The best thing is to save up all the power-hungry things for sunny days. That's things like laundry or big baking sessions. If you're at home, then it's hardly worth bothering with timers, just don't turn on everything at once.



    You can run electric heaters off solar, but unless it's actually sunny, they will most likely be using more electricity than you're generating. If that's the case, then the gas central heating is likely to be cheaper. So it's only useful when it's cold and sunny (like this morning), but not in the summer when you don't need heating, nor on grey, miserable days in the winter.



    If you have a hot water tank, consider whether it's worthwhile to get one of the solar diverters that runs the immersion heater when you have excess electricity. But do the sums - in my case, I decided that the return on investment wasn't really worth it.
    If it sticks, force it.
    If it breaks, well it wasn't working right anyway.
  • edited 7 December 2014 at 11:01AM
    legoman62legoman62 Forumite
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    edited 7 December 2014 at 11:01AM
    Ectophile wrote: »

    If you have a hot water tank, consider whether it's worthwhile to get one of the solar diverters that runs the immersion heater when you have excess electricity. But do the sums - in my case, I decided that the return on investment wasn't really worth it.

    If you're are handy at DIY, and are prepared to swap

    your 3kW immersion for a 1kW one you could use

    energysavingexp's excellent low cost idea at under £20.00 + immersion:D

    I've used it for almost 3 years, with almost no use of my gas boiler during the Summer months, and spent £12.00 maintaining it over that period.:beer:
    if you have solar pv and want to use unused power that would be exported, to heat your hot water or heater etc.
    but don't want to use imported leccy when you are using more than you are producing ie.
    say you are exporting 1.5kw- 4kw and want to use it say running a heater when you are out
    light switch or current switch will turn on your heater but if you turn on say a kettle you will now be using imported leccy (not good)
    this system turns off the heater if you are using more leccy than your production so if its a bright day your heater turns on until a cloud comes over or you turn on a kettle or tumble dryer
    then when kettle has boiled the heater turns back on again
    you can build the device for around £15 if you are good at diy
    if you want to know more about it message me and ill try and explain better
    16 Sanyo Hit 250s.4kWp SMA 3.8kWp inverter. SW roof. 28° pitch.
    Minimal shade. Nov 2011 install. Hybrid car. N.E Lincs Coast.
  • EricMearsEricMears Forumite
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    legoman62 wrote: »
    If you're are handy at DIY, and are prepared to swap your 3kW immersion for a 1kW one you could use energysavingexp's excellent low cost idea at under £20.00 + immersion:D
    I've used it for almost 3 years, with almost no use of my gas boiler during the Summer months, and spent £12.00 maintaining it over that period.:beer:


    Or even easier, do as I have done and slip a 230/115 transformer into an immersion circuit when a (fairly typical) 3kW element gets downrated to 750W. I think I paid £15 for my 'builders site transformer'. I've also got a Wattson meter in my house so was able to add an 'Optiplug' to ensure that whenever there's a spare 750W, the immersion heater fires up.

    Of course, neither approach will work if a house has a combi boiler and hence no possibility of using an immersion heater :cry:
    NE Derbyshire.
    4kWp S Facing 17.5deg slope (dormer roof).
    BEV : Nissan Leaf e+
  • edited 7 December 2014 at 3:19PM
    vix2000vix2000 Forumite
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    edited 7 December 2014 at 3:19PM
    I'm a little confused now!!! The salesman told me that we had the maximum panels for the government pay back scheme. He also told us that the electricity we use would be free from dawn until dusk. He described the methods he uses at home, ie: timers on major appliances, slow cooker, immersion heater etc. So has he given me incorrect information? I know he probably wanted the sale but maybe I misunderstood what he was saying.
  • EctophileEctophile Forumite
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    You may have the more modern and efficient panels. I have 18 panels, and am slightly under the maximum at 3.4kW. With the newer (and more expensive) panels, you can get more power out of each panel, and 16 could be close to 4kW.

    The newer panels may also cope better with poor light. But even so, on a cloudy day, you will probably only generate enough for the "base load" - fridges/freezers, things on standby, a few lights, etc. Power-hungry appliances, such as cookers and tumble driers can take 2-3kW each, and so will use far more than you generate on a cloudy day.
    If it sticks, force it.
    If it breaks, well it wasn't working right anyway.
  • theboylardtheboylard Forumite
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    Hmmmm.... are you paying for the panels, or is it a rent-a-roof company, where they pay for the install and you get the free electricity they generate?*

    If you're paying, then they should have given a quote for the total price, with the make/model of panels and inverter, included dc and ac switches, cable, roof mounting system, guarantee details (whether insurance backed or the"company" guarantee them), a forecast figure of what the install should generate per annum (which should be somewhere in a range of 3500kWh to 3900kWh, give or take 2-300kWh) and obviously they have a company name and did they take a deposit?

    If you could provide some of the info above, then there are plenty on here who can give some honest practical advice on whether you've got a great deal, or maybe you've been oversold?

    Unfortunately, like double glazing and financial services, there are a lot off people who promise far more than they are delivering, better to get a sanity check before you commit cold hard cash!

    I don't particularly like the comment about free electric from dawn to dusk.
    Hugely open to misinterpretation?
    4kWp, SSE, 16 x 250w EcoFuture BoB with retro-fitted SolarEdge P300 optimisers & SE3500 Inverter, in occasionally sunny Corby, Northants.
  • tunneltunnel Forumite
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    vix2000 wrote: »
    I'm a little confused now!!! The salesman told me that we had the maximum panels for the government pay back scheme. He also told us that the electricity we use would be free from dawn until dusk. He described the methods he uses at home, ie: timers on major appliances, slow cooker, immersion heater etc. So has he given me incorrect information? I know he probably wanted the sale but maybe I misunderstood what he was saying.


    My guess is that the salesman is a former double glazing salesman who has been given a script to read from. When my parents had an install I made sure I was there when they all gave their "pitch", 3 out of 4 all came up with very similar responses to your own, they'll tell you what you want to hear to secure a sale. Do you still have a cooling off period(when did you sign for them?) and as theboylard says...more details required...then and only then can anyone clarify whether what the salesman has told you holds any truth


    tunnel
    2 kWp SEbE , 2kWp SSW & 2.5kWp NWbW.....in sunny North Derbyshire
  • ed110220ed110220 Forumite
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    He may have (over)simplified things, maybe he wasn't well informed himself or maybe was intentionally misleading you.

    People often oversimplify things by talking of solar PV in terms of number of panels. This can be quite misleading as not all panels are the same wattage or physical size. It's a bit like talking of buying milk in terms of bottles, without realising that milk comes in very different bottle sizes.

    If you're thinking of trying to replace gas heating with electricity be very careful (I'd almost just say don't) as electricity is much more expensive than gas, and a lot more harmful to the environment when imported from the grid. For example we pay 3.76p/kWh for gas and 12.72p/kWh for electricity. Your main demand for heating will be in the winter when the solar PV is producing little and will only be able to meet a small fraction of your heating needs. What you are likely to end up doing is thinking "great I've got this free electricity during the day, I'll use it with a night storage heater". Then you find that the solar electricity only meets say 10% of the heater's needs and you're having to import the other 90%, working out more expensive then just using the gas central heating...

    Ed
  • Martyn1981Martyn1981 Forumite
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    vix2000 wrote: »
    I'm a little confused now!!! The salesman told me that we had the maximum panels for the government pay back scheme. He also told us that the electricity we use would be free from dawn until dusk. He described the methods he uses at home, ie: timers on major appliances, slow cooker, immersion heater etc. So has he given me incorrect information? I know he probably wanted the sale but maybe I misunderstood what he was saying.

    Hiya vix.

    I'm not usually the kindest when it comes to talking about PV salespeople, but I kinda understand why 4kWp (assuming 16 * 250Wp panels) is often referred to as a limit ...... when it's not.

    The UK FiT rate drops 10% if you go over 4kWp, and not just the bit that's over, but the whole lot.

    UK house roofs aren't particularly large, so most probably can't fit more than 4kWp on a single roof.

    The DNO's (District Network Operators) have to be informed about all systems that are connected to the grid. This can be done afterwards. But for any that could export more than 3.68kW, they need to be asked for prior permission, so it gets a bit more complicated. In your case, if 4kWp of panels, I'd expect them to install a 3.68kW capped inverter, which will work fine.

    Because of these complimentary factors (and I think it's a pure coincidence they match up) most installers, and many PV'ers tend to refer to 4kWp as a max ...... when it isn't really.

    I'm a fan of going larger, where possible, and with a split system that points in different directions, they can share a smaller inverter as they won't peak at the same time. But for you, south facing, might mean a larger inverter and the need for prior approval from the DNO. Add to that the confusion of explaining to you that the subsidy would go down, so you need a larger system to make up the difference etc etc and I think you can excuse the salesman for not wanting to bother. Ok, reluctantly excuse the salesman.

    For leccy heating, I use an oil filled radiator which I run on a 400W setting, it won't heat a room up at this time of year, but will keep the chill off. In Mch/Apr and Sept/Oct it might gently heat a room up. But you need to know what you're generating to make sure that you aren't importing any expensive leccy.

    Also your roof pitch (being south facing) is important, a steep roof will generate more in the winter than a shallow roof (and vice versa in the summer).

    As others have said, that dawn to dusk comment is a very misleading. You will generate for most of that period, unless the weather is bad, but that doesn't mean it'll be enough to match your demand. Any shortfall will be imported - switch a 3kW kettle on when generating 100W and you'll be buying the other 2,900W.

    You can check out the PV FAQs (that lots of us PV'ers put together, including several who have posted on this thread) for some general info and advice.

    Mart.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
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