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Solar thermal panels

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  • Rosa_Damascena
    Rosa_Damascena Posts: 6,979 Forumite
    Fifth Anniversary 1,000 Posts Homepage Hero Name Dropper
    edited 3 September 2020 at 6:57AM
    This posts are really helpful, thank you.

    I found the first winter in the house to be harsh, it was extremely cold but conversely summer 2018 was crazily hot. The south facing conservatory was roasting, and it made me think that if the excess heat should be stored as energy the house would feel more comfortable in the winter without breaking the bank. 2019 and 2020 have been nowhere near as consistently hot, yet the thermometer in the conservatory routinely reaches its maximum of 50°C.

    Last year I had a load of work done, including loft insulation and addressing damp problems which involved stripping the render back on 2/3 of the house, and insulating it before re-rendering it. (I left the south side of the house knowing that I would be remodelling the rear conservatory and would repeat the same when the build was done). The roof will also need some attention within the next couple of years, and I would rather rebuild it than patch it up. So there is potential to reduce the energy bills further when both happen.

    Net result to date: dual fuel bill reduced from nearly £800 pa (estimation based on Q1 2018) to one that is closer to £450. The house does feel warm in the winter without having the thermostat hoiked up too high, but bear in mind I can only be in one room at a time and naturally gravitate to the warmest room. I know that the bill is comparatively low and that the initial outlay of the photovoltaic cells means that I may not see a return in my lifetime. 

    That doesn't stop me thinking the excess heat in the summer could be put to better use, especially as my expansion plans get underway!! My fantasy is that my home will be temperate year-round and the net fuel bill will be zero. If I could sell excess back to the grid, that would be even better.
    No man is worth crawling on this earth.

    So much to read, so little time.
  • Doozergirl
    Doozergirl Posts: 34,075 Forumite
    Part of the Furniture 10,000 Posts Name Dropper Photogenic
    edited 3 September 2020 at 8:03AM
    What you sell back to the grid is a much lower rate than what you have to buy it from them for!  

    There's no benefit to selling to the grid, it reduces your savings and increase the payback time even further.   You need to capture all the energy reaped and use it, except it's expensive to capture.  Again, you can't even sell solar thermal energy (that heats your conservatory) back to the grid either, only use it to heat water, but you're not going to put panels on the conservatory either.     

    There's no way you can hold energy from the summer and hold it through to winter, unless you're a millionaire and not interested in money saving at all.  

    You've got excess heat because you own a greenhouse.   That isn't going to change because you've added solar panels - your house isn't going to be temperate because of it, only pure energy efficiency measures to the fabric will do that, often referred to as 'fabric first'.  It prevents the energy usage in the first place.  Only at that point, when you have money to burn, do renewables come into it.  

    I've literally design my house from the ground up to be temperate all year round.  The standard is called Passive House, have a google.  You can retrofit houses.   It genuinely has nothing to do with solar panels, they are an add-on rather than an adjustment to the fabric. It's insulated to the hilt and has managed ventilation with heat recovery to keep a portion of the heat in during winter.  

    There is a hierarchy of what reduces your bills depending on payback time.   Insulation first, sealing up excess draughts, decent glazing, changing your lightbulbs makes a significant difference, even how you dry your washing will reduce bills.  Changing some appliances might even pay back faster.  

    If you do replace the roof then solid insulation will be less leaky than rockwool.  It's more expensive, but will give you a nice, clean loft space as well.    

    Solar panels, whether ST or PV are a hobby at the moment, not a reasonable cost saving measure, nor a way of making your house temperate.  




    Everything that is supposed to be in heaven is already here on earth.
  • What you sell back to the grid is a much lower rate than what you have to buy it from them for!  

    There's no benefit to selling to the grid, it reduces your savings and increase the payback time even further.   You need to capture all the energy reaped and use it, except it's expensive to capture.  Again, you can't even sell solar thermal energy (that heats your conservatory) back to the grid either, only use it to heat water, but you're not going to put panels on the conservatory either.     

    There's no way you can hold energy from the summer and hold it through to winter, unless you're a millionaire and not interested in money saving at all.  

    You've got excess heat because you own a greenhouse.   That isn't going to change because you've added solar panels - your house isn't going to be temperate because of it, only pure energy efficiency measures to the fabric will do that, often referred to as 'fabric first'.  It prevents the energy usage in the first place.  Only at that point, when you have money to burn, do renewables come into it.  

    I've literally design my house from the ground up to be temperate all year round.  The standard is called Passive House, have a google.  You can retrofit houses.   It genuinely has nothing to do with solar panels, they are an add-on rather than an adjustment to the fabric. It's insulated to the hilt and has managed ventilation with heat recovery to keep a portion of the heat in during winter.  

    There is a hierarchy of what reduces your bills depending on payback time.   Insulation first, sealing up excess draughts, decent glazing, changing your lightbulbs makes a significant difference, even how you dry your washing will reduce bills.  Changing some appliances might even pay back faster.  

    If you do replace the roof then solid insulation will be less leaky than rockwool.  It's more expensive, but will give you a nice, clean loft space as well.    

    Solar panels, whether ST or PV are a hobby at the moment, not a reasonable cost saving measure, nor a way of making your house temperate.  




    I knew I could trust you to give me straight-talking advice!

    The conservatory will be turned into an orangery so the polycarbonate roof will be gone and the ceiling and external walls will be insulated. Am also planning on turning my garage into an orangery kitchen, which will benefit from the same. I originally wanted UFH in both but have realised this is an expensive way of keeping a single room warm. Am starting to wonder if I should have a separate heating system for the "new" part of my house as there is little point in heating the whole house if I am using just these living areas.
    No man is worth crawling on this earth.

    So much to read, so little time.
  • Slinky
    Slinky Posts: 11,011 Forumite
    Part of the Furniture 10,000 Posts Photogenic Name Dropper
    edited 3 September 2020 at 5:17PM
    We were all set to sign up for solar earlier this year then Covid kicked a massive hole in our investments and we scrapped the idea.  The panels were going to be £7-8K and our electric bill is around £500 a year. 
    As for panels for heating hot water, we're only using hot for a couple of showers a day, some hand washing and washing up. In the summer the ancient gas boiler is just heating the hot water tank, and we're only spending £12 a month on gas, including use of the hob, so it's probably costing us £2 a week in gas for hot water. Most washing machines and dishwashers are cold fill so you can't even get any benefit of using your own heated water there.
    We would have loved to do it from the 'eco' point of view, but the sums just didn't add up.
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  • Mickey666
    Mickey666 Posts: 2,834 Forumite
    1,000 Posts Photogenic First Anniversary Name Dropper
    What you sell back to the grid is a much lower rate than what you have to buy it from them for!  

    There's no benefit to selling to the grid, it reduces your savings and increase the payback time even further.   You need to capture all the energy reaped and use it, except it's expensive to capture.  Again, you can't even sell solar thermal energy (that heats your conservatory) back to the grid either, only use it to heat water, but you're not going to put panels on the conservatory either.     

    There's no way you can hold energy from the summer and hold it through to winter, unless you're a millionaire and not interested in money saving at all.  

    You've got excess heat because you own a greenhouse.   That isn't going to change because you've added solar panels - your house isn't going to be temperate because of it, only pure energy efficiency measures to the fabric will do that, often referred to as 'fabric first'.  It prevents the energy usage in the first place.  Only at that point, when you have money to burn, do renewables come into it.  

    I've literally design my house from the ground up to be temperate all year round.  The standard is called Passive House, have a google.  You can retrofit houses.   It genuinely has nothing to do with solar panels, they are an add-on rather than an adjustment to the fabric. It's insulated to the hilt and has managed ventilation with heat recovery to keep a portion of the heat in during winter.  

    There is a hierarchy of what reduces your bills depending on payback time.   Insulation first, sealing up excess draughts, decent glazing, changing your lightbulbs makes a significant difference, even how you dry your washing will reduce bills.  Changing some appliances might even pay back faster.  

    If you do replace the roof then solid insulation will be less leaky than rockwool.  It's more expensive, but will give you a nice, clean loft space as well.    

    Solar panels, whether ST or PV are a hobby at the moment, not a reasonable cost saving measure, nor a way of making your house temperate.  




    I knew I could trust you to give me straight-talking advice!

    The conservatory will be turned into an orangery so the polycarbonate roof will be gone and the ceiling and external walls will be insulated. Am also planning on turning my garage into an orangery kitchen, which will benefit from the same. I originally wanted UFH in both but have realised this is an expensive way of keeping a single room warm. Am starting to wonder if I should have a separate heating system for the "new" part of my house as there is little point in heating the whole house if I am using just these living areas.
    That's exactly what I've done.  Three zones so far and more on the way as refurbishment progresses.  No point in even trying to centrally heat 685m2 of floorspace.  I have rooms with no heating at all, but my winter living spaces are toasty warm.
    Don't entirely discount UFH though (except, perhaps, as a retrofit).  It's no more expensive to run than conventional radiators, indeed the floor is just one giant radiator so it can be run at a lower temperature while giving the same heating effect.

  • Mickey666 said:
    What you sell back to the grid is a much lower rate than what you have to buy it from them for!  

    There's no benefit to selling to the grid, it reduces your savings and increase the payback time even further.   You need to capture all the energy reaped and use it, except it's expensive to capture.  Again, you can't even sell solar thermal energy (that heats your conservatory) back to the grid either, only use it to heat water, but you're not going to put panels on the conservatory either.     

    There's no way you can hold energy from the summer and hold it through to winter, unless you're a millionaire and not interested in money saving at all.  

    You've got excess heat because you own a greenhouse.   That isn't going to change because you've added solar panels - your house isn't going to be temperate because of it, only pure energy efficiency measures to the fabric will do that, often referred to as 'fabric first'.  It prevents the energy usage in the first place.  Only at that point, when you have money to burn, do renewables come into it.  

    I've literally design my house from the ground up to be temperate all year round.  The standard is called Passive House, have a google.  You can retrofit houses.   It genuinely has nothing to do with solar panels, they are an add-on rather than an adjustment to the fabric. It's insulated to the hilt and has managed ventilation with heat recovery to keep a portion of the heat in during winter.  

    There is a hierarchy of what reduces your bills depending on payback time.   Insulation first, sealing up excess draughts, decent glazing, changing your lightbulbs makes a significant difference, even how you dry your washing will reduce bills.  Changing some appliances might even pay back faster.  

    If you do replace the roof then solid insulation will be less leaky than rockwool.  It's more expensive, but will give you a nice, clean loft space as well.    

    Solar panels, whether ST or PV are a hobby at the moment, not a reasonable cost saving measure, nor a way of making your house temperate.  




    I knew I could trust you to give me straight-talking advice!

    The conservatory will be turned into an orangery so the polycarbonate roof will be gone and the ceiling and external walls will be insulated. Am also planning on turning my garage into an orangery kitchen, which will benefit from the same. I originally wanted UFH in both but have realised this is an expensive way of keeping a single room warm. Am starting to wonder if I should have a separate heating system for the "new" part of my house as there is little point in heating the whole house if I am using just these living areas.
    That's exactly what I've done.  Three zones so far and more on the way as refurbishment progresses.  No point in even trying to centrally heat 685m2 of floorspace.  I have rooms with no heating at all, but my winter living spaces are toasty warm.
    Don't entirely discount UFH though (except, perhaps, as a retrofit).  It's no more expensive to run than conventional radiators, indeed the floor is just one giant radiator so it can be run at a lower temperature while giving the same heating effect.

    UFH would have been a nice touch but I discounted it because electric is expensive. With GCH I would be worried about burst pipes and having to lift up flooring in living areas (strangely I can accept it for bathrooms!). AIBU?
    No man is worth crawling on this earth.

    So much to read, so little time.
  • Mickey666
    Mickey666 Posts: 2,834 Forumite
    1,000 Posts Photogenic First Anniversary Name Dropper
    Fair comment about electric UFH being expensive (though mainly because it's electric rather than because it's UFH as such) - I was thinking about 'wet' UFH connected into the standard CH system.
    I suppose burst pipes could be a risk but no more than other water pipes, I'd have thought.  In fact, pipes specifically designed to be embedded in a floor slab would - I would guess - likely be more durable than ordinary water pipes clipped to a wall or running under floorboards.
  • ^^ Do you live in a mansion btw?
    No man is worth crawling on this earth.

    So much to read, so little time.

  • The conservatory will be turned into an orangery so the polycarbonate roof will be gone and the ceiling and external walls will be insulated. Am also planning on turning my garage into an orangery kitchen, which will benefit from the same. I originally wanted UFH in both but have realised this is an expensive way of keeping a single room warm. Am starting to wonder if I should have a separate heating system for the "new" part of my house as there is little point in heating the whole house if I am using just these living areas.
    Yes, absolutely. And the good news is that it's easy. A small electrically-operated 'zone' valve will control the boiler water to that zone, and you'll have a room stat in each zoned area to control it. The cost of adding these bits when you convert/rebuild the connie in to an orangery will be minimal. 

    Worth getting a quote for wet UFH too in case it turns out to be tempting. Yes it'll cost more than radiators, but it's far more comfortable and pleasant to experience, and uses a lower water temp too so your boiler will be running a bit more efficiently. 

    You've done the big jobs with the rest of your house - adding insulation to the walls and ceilings. That leaves your floor! Insulation here isn't nearly so important - not nearly as effective - but making the floor draught-proof is a biggie if it happens to be made from traditional floorboards. In our '30s house, it's not cold weather that makes it chilly but when it's also windy. Lawd, the draughts... :-(  
  • snowcat75
    snowcat75 Posts: 2,283 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Photogenic
    I'd assumed you meant solar thermal panels, Rosa, when you mentioned capturing the heat from your roof, but you may have been thinking of PV panels which produce electricity?

    The Thermal panel is simply heated up by the sun (doesn't even have to be 'sunny') and this heat is transferred to your hot water cylinder. You typically only install 2 or 3 panels, but even that will cost £housands on a retro-fit. It'll save you - ooh, I dunno - a £undred or so per year by warming up your hot tank? Ie - not cost effective (unless you can get it done cheaply). 

    The other system is PV panels and these produce electricity from light which can then be used to power anything in your home, including heating up your hot tank via an immersion heater. You usually have to fit a fair number to get a useful output - say at least 10. This used to be viable - eg a 10-year return on your money - because the gov invested heavily in it, giving generous payments for the leccy generated. That is no longer the case, but the cost has tumbled, now around half or less (~£5k for an install?). 

    On a good sunny day, this can power even high-powered appliances such as washing machines, driers and cookers, but only for as long as the sun is shining brightly; power falls off rapidly on cloudy days. To take full use of this, you either need to be at home when the sun is out, time your appliances to run during the day, or else store the power in batteries. A battery also costs around £5k...

    So is it worth it? No, not until either fuel prices soar or financial assistance is given.

    Really, these are only worth considering as a new install - eg a new build, or a renovation - as to retro-fit them is more involved and costly.

    We looked at a house recently - a converted village hall - and it was powered solely by electricity; a large bank of PV panels (at least 4kW's worth) and a battery. Their energy supplier was specifically designed for this system - they could 'pinch' any surplus power at times of high demand (even from their battery!), and would then return it at times of low leccy cost. I think I recall the annual energy bill was estimated to approach £2k (4 bed house), so this was actually not too bad in a village with no mains gas; when oil prices were high, it would have been similar to this (tho' oil is cheap at the mo').

    I have to say it was tempting; as oil prices increase again, and as energy prices do ditto, this system should become quite competitive - and it's a nice feeling that it's all quiet and clean.

    Bottom line - unless the gov gives grants or other incentives to add panels (of either type) to your roof, it won't be cost effective. If, however, you were carrying out a new build or complete renovation, then it should be considered.
    We're building our own house with gas available on the road.  We looked into it all and solar just doesn't pay, presently.  

    The house is as insulated and airtight as it can be, keeping the heating bills down - and that cost a large amount itself!  But solar would take 20 years to pay off, with or without batteries, or using ASHP to use more of the electricity produced immediately and using 3x less energy than gas.  I did all the calcs myself (with help from the forumites at Buildhub to translate the jargon for me).  It wasn't an experience I enjoyed.  The maximum we could save was £400 a year, with optimal sunshine and an ASHP would still be 2x the energy cost of gas, without considering the much larger outlay. 

    We've run piping and power to the site of a potential future air source heat pump.  When the gas boiler comes to the end of its life and our governments make it viable, we'll go the whole hog and switch to using solar and have an all-electric house.  

    I don't think it's worth it at all at the moment, sadly.  

    I did just the same calc, and it was far better to just put the oil fired in, The trick is as you know is to insulate the places so they require little heat in the first place.... I am tempted to put a thermal store in with solar for H/W but this would be far more of a project for my own amusement than some great money saving device.

    One thing I really like is the UFH really efficient and keeps the place very warm, probably 2 warm but I would never go back to rads.
    The only thing I would say with UFH is you really need a secondary source for autumn, spring as it just doesnt get cold enougth to run the heating as once there 14T of concreates warm there's heat there for 2 days!.
    I also have a backup generator power cuts are fairly common here and its good to be able to keep the house on as we lose everything not having mains gas when it happens. 


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