Heating and Cooling for the Next House - Solar - PV - Heat Pumps - AC

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  • QrizB
    QrizB Posts: 13,629
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    edited 31 May 2023 at 2:40PM
    bhjm said:
    `Martyn1981 said:
    Same thoughts from me. Forget the solar thermal, it's no longer competitive with PV, and leccy (electricity) generation can be used to heat water if you need it.

    has PV become much more efficient in recent years?

    It's not so much that solar PV systems have become more efficient (although as Martyn says it's about 1/3more efficient than it was a decade ago) it's that it's fallen dramatically in price while solar thermal hasn't.
    15-20 years ago the cheapest way to get solar hot water was solar thermal. Today, the cheapest way is solar PV. Over that period, the price of solar PV has fallen by about 75%.
    You can even buy a "solar hot water" kit now which is a couple of PV panels and a matched immersion heater!
    N. Hampshire, he/him. Octopus Go elec & Tracker gas / Shell BB / Lyca mobi. Ripple Kirk Hill member.
    2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 3.6kw inverter. 30MWh generated, long-term average 2.6 Os.
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  • bhjm
    bhjm Posts: 341
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    QrizB said:
    bhjm said:
    `Martyn1981 said:
    Same thoughts from me. Forget the solar thermal, it's no longer competitive with PV, and leccy (electricity) generation can be used to heat water if you need it.

    has PV become much more efficient in recent years?

    It's not so much that solar PV systems have become more efficient (although as Martyn says it's about 1/3more efficient than it was a decade ago) it's that it's fallen dramatically in price while solar thermal hasn't.
    15-20 years ago the cheapest way to get solar hot water was solar thermal. Today, the cheapest way is solar PV. Over that period, the price of solar PV has fallen by about 75%.
    You can even buy a "solar hot water" kit now which is a couple of PV panels and a matched immersion heater!
    thanks - I remember growing up having Solar Thermal heating, early 90ies installed and it saved a fortune of money.
  • bhjm
    bhjm Posts: 341
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    bhjm said:
    `Martyn1981 said:
    Same thoughts from me. Forget the solar thermal, it's no longer competitive with PV, and leccy (electricity) generation can be used to heat water if you need it.

    Definitely max out the PV, but can you get power from the garage to your house, as they aren't physically attatched? Maybe you have a power cable (lights, socket etc), but could make PV tricky.

    Being mid terrace, your heating needs should be much less, and hopefully the walls are well insulated. You can improve the loft if necessary. So, got to be heat pumps, at least I think so. ASHP connected to the current 'wet system' may be fine, but A2A as Screwdriva mentions, could be a goer, and then you get your AC too if needed.

    You could also consider a 'hybrid system', a route I'm leaning towards. So keep the boiler for now, try to reduce gas consumption by installing the A2A units, and if that works well, which it has for us, then stage 2 .....

    ..... replace the old combi boiler with a much smaller gas boiler for heating, and then add a HPWH (heat pump water heater) (again as suggested). Also possibly add another A2A unit, depending on planning rules.
    thanks a lot !

    has PV become much more efficient in recent years?

    Garage and House arent physically attached correct. And there is currently NO electrical connection to the garage. There is a pathway from the garden to the Garage - I was thinking to have a connection put in regardless of PV etc for an electric car to be charged in front of the Garage and to have electricity in the garage too. Would this change something? I hope :-)

    Walls - taking this from the EPC. Wall Cavity wall, as built, insulated (assumed) below is the rating from the EPC. Do these number add up? What do you think?

    what is ASHP & A2A? - sorry these abbreviations confuse me.

    what is stage 2 you are mentioning?

    regarding planning rules, is there currently in place etc? or would this somewhere in the deed mentioned?

    So let`s take Solar Thermal of the list. We are left with the following.

    - AC  (is this the Air to Air) unit / split units you are referring to?
    - PV with or without battery
    - downgrading the Water Boiler

    Hiya, sorry for throwing so much at you, and all the abreviations, I'll run through your points in order, and also try to include as many abbreviations I can think of, that you may come across whilst chatting on here. Hope I'm, not being patronising, as your english skills are excellent, but many terms will reflect common British slang so I'll deliberately throw in as many as I can think of:

    First, yes, PV has become more efficient. My 2011/12 installs are around 15% efficient, now you'll be getting 20(ish)% panels. And whilst that's 'only' a 5% increase from 15-20%, it's a 33% increase in output/generation. For physical size, my older 235Wp and 250Wp panels would now be equivalent to panels in the range of 350-370Wp (and rising). Also costs have fallen over the last decade, hence why solar thermal has fallen out of favour.

    [The rating is power output at peak (p), since performance varies not just by sunshine, angle and clearness of sky, but also air temp and wind, which affect the panel temp and output).

    Second, the garage. Assuming you are allowed to run a cable (have some sort of rights), then that's a good idea. You might consider a small consumer unit (CU) in the garage, and you could have a separate PV system that feeds back into that CU, and then back down to the house. It may be possible to connect the garage and house panels together, but that will involve a long DC (direct current) cable run, which may be too much trouble. If you think the garage roof is worth considering, then I'd suggest making sure the planned cabling is large enough and takes account of your plans. Nothing serious here to consider, just best to build it with the necessary capability. In fact ..... leaping ahead now, if you want to get a BEV (battery electric vehicle) in the future, then you may want to consider a meaty power cable from house to garage, capable of 7kW+.

    Thirdly, walls, I'd assume from the age of the property that it has insulated walls (front and back), and that's a good EPC rating. I'd also assume that the loft is 'well' insulated, but since 2008/2009, recommendations keep rising, so probably worth checking how much insulation there is, and topping up. This is one of the simplest and cheapest ways to reduce heat loss.

    Fourthly, ASHP and A2A. The most commonly referred to heat pumps are air source heat pumps (there's also ground source and water source). So that's a large unit outside that provides hot water for your 'wet' heating system and a tank of hot water for washing etc (DHW - domestic hot water). A wet system is one that uses water, typically feeding radiators (you'll see the abbreviation 'rads' used a lot) and/or underfloor heating. As you say the property has a boiler, then that will be GCH (gas central heating), using rads.

    A2A is air to air heat pumps, or often called air con. The modern units can operate as heat or cold. So some of us have installed one or two, and use excess generation from the PV panels to help heat the house when heating needs are lower - typically we refer to these as the 'shoulder months', perhaps Mch and April and September and October. But PV and A2A may be able to top up heating in colder months, on sunny days.

    Lastly, stage 2. Sorry for the confusion, I meant that for myself, stage one is the rollout of two A2A units, which has helped reduce our gas consumption. And I'm considering (and you may want to think about it), stage two, which instead of replacing the GCH system with a full ASHP (as it's tricky for our house), to further reduce our gas consumption by replacing the current boiler which heats the rads and DHW, with a much smaller boiler*, that only heats the rads. I would then add a HWHP tank (a hot water heat pump tank) that provides the DHW from electricity (leccy). And also, possibly, add a third A2A unit.

    *Much smaller boiler, as ours was installed nearly 25yrs ago, and since then we've managed to massively improve the house, and reduce heating needs. Then reduced GCH needs further with the A2A units.

    Oops, almost forgot your planning question. I mentioned planning as you will need PP (planning permission) if the ASHP outside unit is within 1m of your boundary (3m in Wales). You also need PP for the A2A units (apparently  ;)).

    thank you, and apologies for making you such a long post ;-D

    first thing first. Garage and the Path. view from the Garage towards the garden. I would assume there is enough space to get a cable down this path?



    overall view - I guess this gives a better picture? Still - house in the Middle with garage in the middle.Photo is taken from the West(ish). Meaning, top of the Photo is facing east, while the right side would be the south.(I hope i made it clear) Noticing, one of the neighbors got already PV? :-)



    Cabling and BEV - I have own & drive a PHEV - and charging it slowly with a normal household plug 16A (although I set the charging Amperage in the car down to 7 or 8A. So far, I am more than happy with the charging time etc, I understand, that a BEV may change this, but I have adapted to the PHEV already, so I will be able adapt again :-) Garage is without power at the moment, so the plan was to put down a cable regardless. Likely I will use the opportunity to put down a cable for the PV and maybe even an ethernet cable.

    What do you mean by Consumer Unit? That is not clear to me, sorry.

    The Loft was inspected, there is some insulation, but for sure not up the the 2023 Building standards :-) I am not worried about it. Walls, EPC rating says the walls are insulated, (assumed) but the Home survey says its not, but could have been standard when the house was built.

    Fourthly, ASHP and A2A., 'wet' heating system and a tank of hot water for washing etc has a boiler, then that will be GCH (gas central heating), using rads.
    yes got "rads" and has a GCH - thanks for the explanation.

    'shoulder months', But PV and A2A may be able to top up heating in colder months, on sunny days.
    that would be an ideal outcome, that the A2A / AC can also assist in warming up the house. 

    Lastly, stage 2. And I'm considering (and you may want to think about it), stage two, which instead of replacing the GCH system with a full ASHP (as it's tricky for our house),
    I have no idea how much that would cost and how much it would save, not being of grid, I would not look into this at the moment. Completely removing an already installed, working system with relatively low running / maintenance cost could come at a hefty price, if PV or alternative heating isn`t working.

    further reduce our gas consumption & HWHP tank
    I had quick reading about HWHP - sounds great, but not very efficient when you have 2 kids - So for me, not a super save option to opt for. Not totally against it, but not convinced yet.

    PP (planning permission) if the ASHP outside unit is within 1m of your boundary (3m in Wales). You also need PP for the A2A units (apparently  ;)).
    my quick google search said that ASHP and A2A should be permitted developments, but maybe I am searching incorrect. Can you perhaps, send a link to a source where it says a PP is now needed?

    Thanks again for your time in replying :-)

    if you have any question, or suggestion please fire away ! looking forward hearing from you.
  • Martyn1981
    Martyn1981 Posts: 14,665
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    Hiya bhjm. No problem with advice, hope it helps. But bear in mind most of this is my opinion, so other thoughts and options may be better. At least you have some time to think about it all.

    So, what's a consumer unit? Have you heard the term 'fusebox', I've added a link just so you can see what I mean. So these handle the distribution of power within the house. Rather than just run a simple cable to the garage, you might be better off installing a small consumer unit (ironically, often referred to as a 'garage unit'), so that the garage can then have a set of circuits, such as lights, sockets, PV and car charger. I've separated the car charger from the normal power sockets, as you might be better off having a dedicated high power cable for it, in fact it may even be a requirement.

    Looks like there is room to run a cable from your house to garage, I'm just wondering what 'rights' you have to install cables along communal places/paths. This is someting you'll need to check, but hopefully it'll be ok. Also wondering if there are some rules about the garage as it's a shared building. maybe you can add PV to the middle part, or you may need agreement from the two neighbours too. I've no idea to be honest. But really worth considering, as your part is presumably over 2m wide, so hopefully 4 panels may fit, or two long panels. And as it's a single storey roof, it's quicker and easy to work on. But (sorry for all the but's, I'm typing and thinking at the same time) .... if the garage PV is a totally separate system, then you might want to think about adding it at a later date, though I'd hope you'd get a better price for doing both at the same time.

    I agree with your general findings about ASHP and A2A. So long as the units aren't too close to a neighbour, or too powerful and possibly noisy, then you should be OK. But I've heard people say that installing a second A2A unit will reguire PP. Sorry to be vague, but that's how the UK planning rules tend to work, they give a general OK ..... so long as ........ with rules that sometimes leave you wondering if you comply or not. If in doubt you can check with the local authority planning department, but their advice may be confusing too.


    Looking longer term, I agree about the hot water. If the current boiler works, and provides heat and DHW, then settle into the house and enjoy it. If after getting PV, and perhaps an A2A unit, you find it works well, then in the future you could think about the hybrid idea I've been pondering, or even replace the gas boiler with an ASHP, that runs the rads and the hot water tank.
    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.
  • Waywardmike
    Waywardmike Posts: 197
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    I'm not sure what you meant by significantly but I'm aware that the difference is < 6 kgs between a 550W and 410W panel from the same brand. This should be a non-issue for any installer. 

    27.5kG (NUJD550, the lightest of the two) Vs. 20.7kg (NUJC410BBLACK, the heaviest of the two), 6.8Kg, nearly 33% heavier,  I'd argue that's pretty significant.  Do you know of any residential install that has these, or an installer that's done it?

    4 Kwp System, South Facing, 35 Degree Pitch, 16 x 250W Solarworld Panels, SMA Sunnyboy 3600 Inverter, Installed 02/09/14 in Sunny South Bedford - £5600
    Growatt AC Coupled SPA3000tl and 6.5kWh battery Installed Apr 2022
  • shinytop
    shinytop Posts: 2,088
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    PP (planning permission) if the ASHP outside unit is within 1m of your boundary (3m in Wales). You also need PP for the A2A units (apparently  ;)).
    my quick google search said that ASHP and A2A should be permitted developments, but maybe I am searching incorrect. Can you perhaps, send a link to a source where it says a PP is now needed?

    Thanks again for your time in replying :-)

    if you have any question, or suggestion please fire away ! looking forward hearing from you.
    These are (afaik) the current rules on heat pumps, including A2A.  

    https://www.planningportal.co.uk/permission/common-projects/heat-pumps/planning-permission-air-source-heat-pump

    Don't believe any claims from manufacturers or installers to the contrary; they are making it up.  You need specific PP for any unit that is used for cooling and for more than one whether used or cooling or not.  Your single heating only unit also has to be no closer than 1m to any boundary. 

    Getting PP isn't a showstopper but some local authorities can be very difficult about noise, especially if a neighbour objects.  
    OTOH, plenty folks bung in ASA units without PP and get away with it.       
  • Newbie_John
    Newbie_John Posts: 376
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    I agree with above comments about solar thermal.. although we got one in 2021 as it was covered by green home grant and we've paid £2k (£6k total cost for 2 panels and 180l tank). 

    My house is similar to yours so I can share some info that I've obtained.
    Per average per person you use about 1.5kW to heat water per day. For family of 4 with a price of 33p per kWh (electricity) that's about £2 a day - about £700 a year.

    Now, we switch off additional electric heating between May-October having 5 months of almost free hot water (yes, there are days with cooler shower 😅) - about £300 saved, for the rest of the year it's a bit of lottery - as even in winter we can get 40°C hot tank on fully sunny day, but there are weeks when it does up to 20°C max. So let's say it does a third - further £130.

    You can also plug dishwasher to the tank having it cheaper.. not so easy with washing machines though.

    So with current prices it saves us up to £450 a year (SE England), but prices are going down, and it's almost impossible for it to pay the full price of £6k back.

  • bhjm
    bhjm Posts: 341
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    Hiya bhjm. No problem with advice, hope it helps. But bear in mind most of this is my opinion, so other thoughts and options may be better. At least you have some time to think about it all.

    So, what's a consumer unit? Have you heard the term 'fusebox', I've added a link just so you can see what I mean. So these handle the distribution of power within the house. Rather than just run a simple cable to the garage, you might be better off installing a small consumer unit (ironically, often referred to as a 'garage unit'), so that the garage can then have a set of circuits, such as lights, sockets, PV and car charger. I've separated the car charger from the normal power sockets, as you might be better off having a dedicated high power cable for it, in fact it may even be a requirement.


    ok - got it. the consumer unit  is for me nothing else than a fuse box :-D and yes - separate cable for a BEV which is more powerful is definitely a consideration. 

    Looks like there is room to run a cable from your house to garage, I'm just wondering what 'rights' you have to install cables along communal places/paths. This is something you'll need to check, but hopefully it'll be ok. Also wondering if there are some rules about the garage as it's a shared building. maybe you can add PV to the middle part, or you may need agreement from the two neighbours too. I've no idea to be honest. But really worth considering, as your part is presumably over 2m wide, so hopefully 4 panels may fit, or two long panels. And as it's a single storey roof, it's quicker and easy to work on. But (sorry for all the but's, I'm typing and thinking at the same time) .... if the garage PV is a totally separate system, then you might want to think about adding it at a later date, though I'd hope you'd get a better price for doing both at the same time.
    the path to the garage itself is not communal area, it`s solely my use. The Garage is, as you correctly identified a shared Garage. Would you know what kind of restrictions there may be could be in place that I am not allowed to put PV on the garage? Do I need my Neighbors consent on a legal basis if it is just on my area of the Garage? The ethical and good neighborhood spirit is certainly excluded from my question ;-) Should there something in the deed? Separate at a later date. Maybe, I think to get it done initially, and than adding the PV to the house if I do it in 2 stages, ideally, finances allowing of course, I would do it all in one go.

    I agree with your general findings about ASHP and A2A. So long as the units aren't too close to a neighbour, or too powerful and possibly noisy, then you should be OK. But I've heard people say that installing a second A2A unit will reguire PP. Sorry to be vague, but that's how the UK planning rules tend to work, they give a general OK ..... so long as ........ with rules that sometimes leave you wondering if you comply or not. If in doubt you can check with the local authority planning department, but their advice may be confusing too.


    a reputable installer from the area should be able to answer these question or would it be only the local council? (sorry I am new into house owning in the UK.
    Looking longer term, I agree about the hot water. If the current boiler works, and provides heat and DHW, then settle into the house and enjoy it. If after getting PV, and perhaps an A2A unit, you find it works well, then in the future you could think about the hybrid idea I've been pondering, or even replace the gas boiler with an ASHP, that runs the rads and the hot water tank.
    yes, that is probably what I am gonna do and see what will happen and how long the boiler may last. May be a bit life extending when I can heat with the AC - Can I call an AC actually an A2A heat pump?
  • bhjm
    bhjm Posts: 341
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    shinytop said:

    PP (planning permission) if the ASHP outside unit is within 1m of your boundary (3m in Wales). You also need PP for the A2A units (apparently  ;)).
    my quick google search said that ASHP and A2A should be permitted developments, but maybe I am searching incorrect. Can you perhaps, send a link to a source where it says a PP is now needed?

    Thanks again for your time in replying :-)

    if you have any question, or suggestion please fire away ! looking forward hearing from you.
    These are (afaik) the current rules on heat pumps, including A2A.  

    https://www.planningportal.co.uk/permission/common-projects/heat-pumps/planning-permission-air-source-heat-pump

    Don't believe any claims from manufacturers or installers to the contrary; they are making it up.  You need specific PP for any unit that is used for cooling and for more than one whether used or cooling or not.  Your single heating only unit also has to be no closer than 1m to any boundary. 

    Getting PP isn't a showstopper but some local authorities can be very difficult about noise, especially if a neighbour objects.  
    OTOH, plenty folks bung in ASA units without PP and get away with it.       
    I am struggling a bit understanding the sentence in bold.

    "In addition, the following conditions must also be met. The air source heat pump must be:
    • Used solely for heating purposes
    • Removed as soon as reasonably practicable when it is no longer needed for microgeneration
    • Sited, so far as is practicable, to minimise its effect on the external appearance of the building and its effect on the amenity of the area.
    what does it mean, If I use the A2A also for cooling? and what is microgeneration?
  • bhjm
    bhjm Posts: 341
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    I agree with above comments about solar thermal.. although we got one in 2021 as it was covered by green home grant and we've paid £2k (£6k total cost for 2 panels and 180l tank). 

    My house is similar to yours so I can share some info that I've obtained.
    Per average per person you use about 1.5kW to heat water per day. For family of 4 with a price of 33p per kWh (electricity) that's about £2 a day - about £700 a year.

    Now, we switch off additional electric heating between May-October having 5 months of almost free hot water (yes, there are days with cooler shower 😅) - about £300 saved, for the rest of the year it's a bit of lottery - as even in winter we can get 40°C hot tank on fully sunny day, but there are weeks when it does up to 20°C max. So let's say it does a third - further £130.

    You can also plug dishwasher to the tank having it cheaper.. not so easy with washing machines though.

    So with current prices it saves us up to £450 a year (SE England), but prices are going down, and it's almost impossible for it to pay the full price of £6k back.

    again, growing up with Solar Thermal of the first generations. We had all year warm (not hot) water which was enough to wash your hands. You don`t always empty the entire tank when using warm water. But yes, if using correctly throughout the house. Washing machine, Dishwater, etc. I imagine, the boiler will switch on less often and for a shorter period of time?

    yes I agree, if it cost 6k - it`s hard to get the money back. If we would talk about 2-3k it is worth considering
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