Iceverge Posted December 4 Share Posted December 4 I think it was @SteamyTea who was of the view that keeping heating and DHW separate was a good idea. We just use an immersion on a TOU tariff of 12c/kWh and a 300l dumb UVC. It's controlled by one of these. A 4kWp PV setup would cost about €7.5k at the moment to pay for it to be installed. Over 25 years that's about 10c/kWh so the case for complicating the system further is very slim. If I DIY install the PV it might be different. Link to comment Share on other sites More sharing options...
SteamyTea Posted December 5 Share Posted December 5 5 hours ago, Iceverge said: I think it was @SteamyTea who was of the view that keeping heating and DHW separate was a good idea. I do. They do different things, at different temperatures and at different times. The 3Ds Link to comment Share on other sites More sharing options...
Boxy Posted December 5 Author Share Posted December 5 20 hours ago, SteamyTea said: Are they going to be grid tied? What is grid tied ????? Link to comment Share on other sites More sharing options...
SteamyTea Posted December 5 Share Posted December 5 2 minutes ago, Boxy said: What is grid tied ????? Is the PV system connected to the main electrical grid. Link to comment Share on other sites More sharing options...
Boxy Posted December 5 Author Share Posted December 5 No I was just going to have roughly 4 panels just for hot water and a bit of electricity I don’t have room for anymore Link to comment Share on other sites More sharing options...
JohnMo Posted December 5 Share Posted December 5 32 minutes ago, Boxy said: No I was just going to have roughly 4 panels just for hot water and a bit of electricity I don’t have room for anymore To do a DC connection to an immersion you either have to impedance of the PV with the immersion. Or get a dedicated DC to immersion to mppt tracker. First is cheap (the immersion to PV) as it's the price of the correct immersion. The other is stupid expensive. To make best use of the PV you need to be grid coupled. So you need panels and an inverter. The price I quoted above was for a full kit AC coupled. Link to comment Share on other sites More sharing options...
SteamyTea Posted December 5 Share Posted December 5 15 minutes ago, JohnMo said: To do a DC connection to an immersion you either have to impedance of the PV with the immersion Is that match the resistance to the PV output, which will vary with light levels. The other problem is switching DC. Link to comment Share on other sites More sharing options...
Boxy Posted December 5 Author Share Posted December 5 2 hours ago, JohnMo said: To do a DC connection to an immersion you either have to impedance of the PV with the immersion. Or get a dedicated DC to immersion to mppt tracker. First is cheap (the immersion to PV) as it's the price of the correct immersion. The other is stupid expensive. To make best use of the PV you need to be grid coupled. So you need panels and an inverter. The price I quoted above was for a full kit AC coupled. 2 hours ago, JohnMo said: To do a DC connection to an immersion you either have to impedance of the PV with the immersion. Or get a dedicated DC to immersion to mppt tracker. First is cheap (the immersion to PV) as it's the price of the correct immersion. The other is stupid expensive. To make best use of the PV you need to be grid coupled. So you need panels and an inverter. The price I quoted above was for a full kit AC coupled. 2 hours ago, JohnMo said: To do a DC connection to an immersion you either have to impedance of the PV with the immersion. Or get a dedicated DC to immersion to mppt tracker. First is cheap (the immersion to PV) as it's the price of the correct immersion. The other is stupid expensive. To make best use of the PV you need to be grid coupled. So you need panels and an inverter. The price I quoted above was for a full kit AC coupled. It was just a idea I’m no electrician or solar expert but I thought it might help with electrical costs for the immersion for hot water for little outlay Link to comment Share on other sites More sharing options...
JohnMo Posted December 5 Share Posted December 5 A video to watch https://youtu.be/kVaxAfXQPDU?si=nIsu2BUM-O5wMIQM Link to comment Share on other sites More sharing options...
Iceverge Posted December 6 Share Posted December 6 6 hours ago, Boxy said: No I was just going to have roughly 4 panels just for hot water and a bit of electricity I don’t have room for anymore As far as i know this might be one of the few remaining justifable use cases for solar thermal. You can get a stand alone heat pump just for DHW too. I've been pondering this. to see if it will reduce our €400/year DHW bill for about 3500kWh at a TOU tariff of 12c. For a capital cost of €1,230 plus bits and pieces and fittings, say €1500 DIY cost. At a COP of 2.5 it would reduce the kWh usage to 1400kWh. However due to the lower storage temperatues I reckon half the heat imput would need to be done at the more expensive daytime rate of 26c/kWh. So 700kWh@12c + 700 kWh@26c = €266 per year. A saving of €134 per year. A payback of about 11 years assuming it doesn't break. I think I'll keep my money in my pocket. Link to comment Share on other sites More sharing options...
Iceverge Posted December 6 Share Posted December 6 (edited) Ok lets play the game with out own situation. Lets DIY/ Electician install some PV. The bits for a 5.8kWp system would come to about €3800. Lets say the install costs €6800 assuming I did the climbing myself and got someone else to do the wiring. PVGIS predicts 5.3MWh of production. Lets say 4.8MWh to be conservative. At a feed in rate of 24c/kWh it's never worth using it to heat water and almost matches the equivilant day tariff. Export would be about €1200 per year. A payback of about 5.5 years. Relatively convincing. Now assume the feed in tarriff doesn't exist. We self consume 4000kWh per year which would otherwise be bought in at a rate of 19c. I reckon payback slips to 9 years. Less convincing but OK. The bottom line is that unless you can't avail of cheap overnight tarriffs or have very very hight water usage I wouldn't get too worried about using a TOU immerson for DHW. Edited December 6 by Iceverge Link to comment Share on other sites More sharing options...
SteamyTea Posted December 6 Share Posted December 6 6 hours ago, Iceverge said: The bottom line is that unless you can't avail of cheap overnight tarriffs or have very very hight water usage I wouldn't get too worried about using a TOU immerson for DHW. Yes, it is the problem I have. I think my daily standing charge is about 75p/day, so close to £300/year before any usage. Taking the 30th November 2024, as I have the numbers to hand, I heated all my water for the day for 62p, supper time was 52p, the rest of the day was £1.37, total was £2.53. So about £1.80 for actual usage (8.4 kWh). I could, and can, reduce that a bit more, but I would then be heading into the realms of personal sacrifice i.e. a shower instead of a bath, but I like a morning wallow, could cook more efficiently and just microwave the left overs, and let the mean house temperature drop a bit more, from about 21°C to 19°C. But at under £3/day for winter usage, I am not going to change. Just makes adding heat pumps and PV not worth it for me. If I had a bigger house, mine is tiny at 48m2 TFA, with a better orientated roof, then maybe, but as I want to move one day soon (been saying that for 18 years), I am not spending any money on the place. Link to comment Share on other sites More sharing options...
Boxy Posted December 6 Author Share Posted December 6 My build is 112 sq m over 2 storeys a2a heating and Mixergy hot water cylinder 3 adults = 3 x 8 min showers in the morning and 2 baths and 1 8 min shower in the evening plus heating and cooking- I’m just trying to avoid £300 plus per month bills in the winter - electric rate about 23 pence per kw normal rate and 10p per kw cheap night tarriff Link to comment Share on other sites More sharing options...
SteamyTea Posted December 6 Share Posted December 6 1 minute ago, Boxy said: 3 adults = 3 x 8 min showers in the morning and 2 baths and 1 8 min shower in the evening Cut down on that is the cheapest. It is kW, not kw. It does make a difference. Link to comment Share on other sites More sharing options...
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