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Solar panels on side of house to heat water

 
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Solar Photovoltaic (PV)
Last Post by Transparent 5 months ago
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 paultheheating
(@paultheheating)
Active Member Member
Joined: 6 months ago
Posts: 13
Topic starter 10/11/2025 10:42 am   [#2582]

One side of our house gets lots of sun and was thinking of having solar panels on the sde wall mounted vertically, then sending generated energy straight to our hot water tank via an imersion heater.

The concept is to raise the water temperature as much as panels can and then use normal gas boiler to to the rest.

Is anyone out there doing something similar? And if so what equipment would I need?  

 



   
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 colinc
(@colinc)
Eminent Member Member
Joined: 7 months ago
Posts: 23
10/11/2025 11:17 am  

Posted by: @paultheheating
↑

One side of our house gets lots of sun

Depends upon several considerations; in no particular order:

  • Actual wall orientation
  • Water heater rating / capacity
  • PV array total Watts peak, one RoT is estimate effociency between 20% - 85%, which is very much dependent upon  weather and seasonality.
  • Battery kWh if that is applicable, again efficiency is seasonal, albeit to a much lesser variance regarding ambient temperature.
  • Do your own due diligence on equipment:  headline numbers are not always aligned with reality.
  • Permitted development rights by your Local Council Planning Officer.
  • Shading caused by trees or buildings
  • Physical protection from potential accidental damage
  • Choose your installer carefully,  caveat emptor.

This list is an uncomptehensive "brain dump", no doubt I will have missed things that hopefully others will point out.

Plenty of good stuff on Youtube, and personally I have found "Gary Does Solar" channel a very informative and helpful  resource.


This post was modified 6 months ago by colinc

   
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 paultheheating
(@paultheheating)
Active Member Member
Joined: 6 months ago
Posts: 13
Topic starter 10/11/2025 12:37 pm  

Thankyou for the brain dump, all very worthy items.

Was really looking for experiences of a range of people that have already installed vertical panels for direct water heating, no batteries no conversion of electical energy, just whatever power generated going straight into an imersion heater in the hot water tank.



   
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Batpred
 Batpred
(@batpred)
Prominent Member Member
Joined: 1 year ago
Posts: 801
29/11/2025 9:27 pm  

@paultheheating 

We are looking into PV panels at the moment. Each panel provides up to around 35V and max 450W. Quick googling shows there are DC water elements.. A barebones system may do something.. Thing to be aware is low voltage transmission has high losses, so you need to try to have a short cable run. As I assume you would not be wiring too many panels serially. 

Let us know how it works! 


8kW Solis S6-EH1P8K-L-PLUS hybrid inverter; G99: 8kw export; 16kWh Seplos Fogstar battery; Ohme Home Pro EV charger; 100Amp head, HA lab on mini PC


   
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 paultheheating
(@paultheheating)
Active Member Member
Joined: 6 months ago
Posts: 13
Topic starter 30/11/2025 4:44 pm  

Thanks for the reply, am not an electrician, so was looking to find other people that have already tried this type of system, ie, vertical panels that directly feed dc immersion. The distance between potental panels and the water cylinder is 40-50ft



   
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Batpred
 Batpred
(@batpred)
Prominent Member Member
Joined: 1 year ago
Posts: 801
30/11/2025 4:54 pm  

Best get an electrician qualified in DC systems. The ones  that install PV are your best bet. 

That sort of distance would lead to high losses with the 40V of a panel


8kW Solis S6-EH1P8K-L-PLUS hybrid inverter; G99: 8kw export; 16kWh Seplos Fogstar battery; Ohme Home Pro EV charger; 100Amp head, HA lab on mini PC


   
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Toodles
 Toodles
(@toodles)
Famed Member Contributor
Joined: 4 years ago
Posts: 2711
30/11/2025 5:12 pm  

@batpred Isn’t the usual solution to use microinverters? The voltage is brought up and also converted to AC before the perilous journey to your CU (via any other control gear of course!) Toodles.


Toodles, heats his home with cold draughts and cooks food with magnets.


   
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Batpred
 Batpred
(@batpred)
Prominent Member Member
Joined: 1 year ago
Posts: 801
30/11/2025 5:38 pm  

Bringing it up to standard ac is what most people would want... 

In my own case, pv power from that string would be coming into my inverter as 200-400V DC... Simplest as I already have the inverter 


8kW Solis S6-EH1P8K-L-PLUS hybrid inverter; G99: 8kw export; 16kWh Seplos Fogstar battery; Ohme Home Pro EV charger; 100Amp head, HA lab on mini PC


   
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Majordennisbloodnok
 Majordennisbloodnok
(@majordennisbloodnok)
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Joined: 4 years ago
Posts: 1759
30/11/2025 5:44 pm  

I have no practical experience here but my instinct would be to make a choice; either solar PV wired up to do more than just immersion heater duties or solar thermal panels for just water heating. I’m happy to be convinced otherwise but it feels as if solar PV panels restricted to just one job are a big compromise. 


105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"


   
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Toodles
 Toodles
(@toodles)
Famed Member Contributor
Joined: 4 years ago
Posts: 2711
30/11/2025 5:50 pm  

@majordennisbloodnok I think that at times of Solar Excess, once the hot water was up to capacity, then a solar water heating system would be wasteful; with solar PV, at least the excess could be used to charge a battery or feed into the domestic power requirement. (And no risk of frozen plumbing in the system during dark winter nights). Toodles.


Toodles, heats his home with cold draughts and cooks food with magnets.


   
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Batpred
 Batpred
(@batpred)
Prominent Member Member
Joined: 1 year ago
Posts: 801
30/11/2025 5:57 pm  

Posted by: @majordennisbloodnok
↑

I have no practical experience here but my instinct would be to make a choice; either solar PV wired up to do more than just immersion heater duties or solar thermal panels for just water heating. I’m happy to be convinced otherwise but it feels as if solar PV panels restricted to just one job are a big compromise. 

I tend to agree, if it involves getting any certified professionals. 

If it is just to wire something directly and keeping costs down, perhaps the break even is possible with a hot water only system. 

 


8kW Solis S6-EH1P8K-L-PLUS hybrid inverter; G99: 8kw export; 16kWh Seplos Fogstar battery; Ohme Home Pro EV charger; 100Amp head, HA lab on mini PC


   
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Majordennisbloodnok
 Majordennisbloodnok
(@majordennisbloodnok)
Famed Member Moderator
Joined: 4 years ago
Posts: 1759
30/11/2025 5:58 pm  

Posted by: @toodles
↑

@majordennisbloodnok I think that at times of Solar Excess, once the hot water was up to capacity, then a solar water heating system would be wasteful; with solar PV, at least the excess could be used to charge a battery or feed into the domestic power requirement. (And no risk of frozen plumbing in the system during dark winter nights). Toodles.

I totally agree, which is why my personal preference would be solar PV that's NOT limited to water-heating duties. However, that's not what @paultheheating seemed to want to consider.

Posted by: @paultheheating
↑

Thankyou for the brain dump, all very worthy items.

Was really looking for experiences of a range of people that have already installed vertical panels for direct water heating, no batteries no conversion of electical energy, just whatever power generated going straight into an imersion heater in the hot water tank.

 

 


105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"


   
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