Sun, 10 May 2026 03:04:59 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11272&Focus=186551#Comment_186551 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11272&Focus=186551#Comment_186551 Tue, 15 Oct 2013 22:59:58 +0100 slidersx200
A local firm(Northern Ireland) with a good reputation currently sells a 2 panel solar thermal system suitable for 4-5 person household for £3000 and a 3.5kW PV system for £6200. They claim payback periods of around 6 years for both. From what I have read, the immersion controllers for PV systems are usually in the region of £500.

The cost of heat pumps, air or ground source can vary greatly and will depend on your home's requirements so I'm not sure what cost is fair to assume for comparison.

A basic observation to get things started would be that the solar thermal only contributes to DHW whereas PV can also offset your general electric consumption and the heat pump should take care of your space heating requirements.

In our climate do you perceive any of these options to be more reliable or with the potential grants and payments could you be swayed on a financial basis?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11272&Focus=186556#Comment_186556 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11272&Focus=186556#Comment_186556 Tue, 15 Oct 2013 23:18:18 +0100 Ed Davies
My calculator for comparison of PV and solar thermal: http://edavies.me.uk/2012/11/pv-dhw/

(Note, the price of the PV panel used there has gone up a bit since, but not enough to swing the basic conclusion.)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11272&Focus=186558#Comment_186558 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11272&Focus=186558#Comment_186558 Tue, 15 Oct 2013 23:38:34 +0100 slidersx200
Another option I neglected to mention previously is the thermo dynamic panels that seem to combine a heat pump with a solar collector. They claim to work even when the sun isn't shining and boast of minimal running costs but as far as I understand do not qualify for grants or payments.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11272&Focus=186561#Comment_186561 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11272&Focus=186561#Comment_186561 Wed, 16 Oct 2013 06:45:20 +0100 SteamyTea What I cannot find out is any reliability data about them and out of the two installers I have spoken to, one refused to get back to me, the other did not fill me with any confidence (just like their windows).


When comparing PV and ST you have to me careful what you are comparing. kWh alone is not much use. It is a good unit to describe PV with as you know (assuming grid tied) that the voltage is 230V (ish). With ST your equivalent to volts is temp, so if your store is cold, your kWh, even in the winter, can look impressive, but you may not get hot enough to be useful and requiring supplementary heating. If your store is hot, your ST adds nothing, so your kWh figure is zero. So you need to look at performance above a set temperature, say 45°C.
As Ed describes on his website, there is a small 'sweet spot' where the two are about even, with the balance in performance and cost being in favour of PV.
It really comes down to how much water you need heated every day and what your weather regime is. Both are variables. PV does not need servicing (though component may need replacing).]]>