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Solar PV/heat pump in a low consumption house

  • 06-02-2021 2:08am
    #1
    Breezer
    Registered Users, Registered Users 2 Posts: 3,228 ✭✭✭


    I’m currently considering a solar PV system, and am trying to decide is it worth it in my case.

    I’m a one person household and likely to remain so. Most of my usage is at night/weekends. I use 2000 kWh of electricity a year. My heating is gas and I use 4000 kWh a year. Total spend €600 a year on electricity, €360 on gas.

    I’ve a nearly due south facing roof, no shade, and can fit up to a 4.5kWp system (this would require me resurfacing a roof though. 3.5 kWp without changing the roof).

    The environmental benefits of a solar pv system appeal to me. But I already buy 100% green electricity from the grid. My main environmental concern is the gas. Would I be better off getting a heat pump, and powering it via green electricity from the grid? I have fairly good insulation, triple glazing etc., but it’s not perfect and would need extra work to address cold spots, and also ductless MVHR to be installed, I think? It’s a 90 year old house that I gutted a few years ago, but obviously has old masonry etc., so sealing it to the standard required of a heat pump may be difficult? And then I’d likely have to change the radiators. I don’t have UFH.

    My current idea is to do the solar thing now, with a battery, while the grants are available. Hopefully start benefitting from an FIT soon. And then install the heat pump down the line.

    Presumably I’d need a fairly large battery to make the solar pv useful in powering the pump? Given my bills aren’t huge, and my concerns are more environmental anyway, would I be better off skipping the solar, putting the money into sealing the house/MVHR, and getting the pump installed now?


Comments

  • #2
    holdfast
    Registered Users, Registered Users 2 Posts: 1,151 ✭✭✭holdfast


    First thing to consider is changing your energy use by switching lights etc, if you have that under control you should look to upgrading the thermal properties of you house. Finally RE tech, only once the other two are in place should you consider them .


  • #3
    Breezer
    Registered Users, Registered Users 2 Posts: 3,228 ✭✭✭Breezer


    holdfast wrote: »
    First thing to consider is changing your energy use by switching lights etc, if you have that under control you should look to upgrading the thermal properties of you house. Finally RE tech, only once the other two are in place should you consider them .

    Thanks. Already done re the lights and appliances. Thermal properties already done to a large extent, although there’s one or two things I need to address (draft still coming in in one spot, chimney needs to be blocked).

    Looking at the quotes I’m getting and the size of my bills, I’m starting to think solar pv isn’t worth it, in my case. Assuming my electricity bill was reduced to zero (which it obviously won’t be), I’m still looking at a 15-20 year pay off. And that won’t actually reduce my carbon footprint at all.

    I think I’ll plug up the drafts, see how much gas I’m using next winter, and then have a think about whether a heat pump is worth it.


  • #4
    headtheball14
    Registered Users Posts: 234 ✭✭headtheball14


    This might be worth a look detailed experience of heat pump installation and electricity consumption in older house. https://trystanlea.org.uk/heatpump2020

    From a financial point of view in my opinion, swapping gas for a heat pump doesn’t make any sense. You would need a heat loss survey which will cost 500 quid and then met its recommmendations .
    solar Pv maybe but just to note, your house will need to get a c ber grade after installation. I would wait till your gas boiler is ready to be replaced and reassess then.


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