Gill

A very basic solar gen calculation from energy saving trust based on postcode. South facing unstructured roof. I estimate 5mx 4m could site panels. This is by no means using any smart sizing based on my energy requirements. It does indicate I've potential to bank a fair amount of excess as hot water (over the sunny months). Now I need to work out how this folds into the maths 🤔 Size of the system 4 kWp Energy generated by the panels 3,213 kWh / year

IT myself for a couple of decades - currently cloud compute with a strong emphasis on security and regulatory compliance. I like a happy medium where I have the option but I maintain full featured control without WiFi. Not a fan of black box solutions where I can get in there and inspect the security setup. That rings alarm bells for me.

Good to know. I'm sure when I was looking previously at the edel, it brought up a list of 'additional product of interest' including required exhaust kit and (optional) wifi hubs. I am a big hater of hubs. Why do I need to route simple api calls through a propriety hub! I have to assume its not required for every day operating. I don't think that's an edel specific issue. Valliant probably the same. More to the point... There's more to the cost than just the unit as is probably true with the UVC. When I spoke to my plumber last year he had zero heat pump experience and his son was just starting to look into it but they had zero demand. Not one single customer. Spoke to a few others who echo this. Those with the experience are hard to find or are operating under 'Green /renewable solutions' type companies which in my limited experience adds a hefty premium to the work. I may have answered my own question. Should take my own advise sometimes and RTM. 'This function enables the appliance to operate in auto-production mode, which means that it will use the energy produced by the PV function to supply the heat pump as well as the electrical back-up, in order to heat the water in the tank.' So potentially increased COP from solar but reduced storage if max temp can only be 65. I should probably size up roof space suitable for solar and work out what I could be storing on a day where we have little sunlight demand.

Thanks - the Edel is a few hundred pounds cheaper which would reduce payback. Do you happen to know about install or maintenance costs? It would be good to factor that in. I may well be missing something on the ESHP but I see max temps around the 65 mark. I can't see an figure for UVC but assuming 90 based on manufacturer datasheet mentioning 'pressure relief value set at 7 bar / 90°C'. I'm think I read on another thread that the eshp might not be the best fit to max out your spare solar due to temp limitations. The other aspect I don't fully understand on the excess solar is if that hooks to an immersion (so 1:1) or if that can flip the heat pump power input automatically giving your solar input an increased COP.

Should that not be (2,300 + (150*5)) / 5 = 610 £/year (750 + (375*7)) / 7 = 482 £/year I prefer you numbers on my pocket mind you. Agree that for smaller usage the outlay is hard to justify. If we were chewing through more DHW then I'd be more inclined to consider ESHP.

I can see time of use tarrifs becoming far more prevalent with the EV use case. Not sure what that means for Eco7 style tarrifs. Really do need a crystal ball for this stuff! There's a part of me that wants ESHP to be the solution but the savings aren't dramatic enough to accept the risk of maintenance /repair on 2.5k system (that few plumbers up my way have the faintest idea about). I'll expect a tap on the shoulder from hindsight in 2030. 😁

Finally got round to doing some sums. Water heating currently around 6kWh daily so with a bit of round up call it 2500 annual. Eshp with a cop of 2.5 would mean a 1500kWh a year reduction saves £225 at my current overnight rate of £0.15 Hopefully these models make firya reasonable comparison. ESHP (Vaillant aroSTOR 270) - £2300 Telford Tempest 300 Indirect Unvented Cylinder TWIN Immersion - £750 So about a 7 year payback assuming identical maintenance costs between both systems. I've not looked at install cost differences. The Telford states lifetime guarantee (I'm sure there are exclusion). The ESHP 5 years on the cylinder and 2 on other components. Adding solar to the mix increases the payback time on the ESHP and I can't help but assume an unvented cylinder will be a cheaper product for repair /maintenance. Unless my maths is way off, looks like UVC with multi immersion is the way to go.

Same situation at my wee caravan on the ayrshire coast. Does make for some splendid Ailsa Craig sunsets mind you. One day I might feel confident enough to build out an all year place there but plenty learning to do before that's feasible.

We're at 18 ish with heating (35 Kwh) yesterday. Tomorrow and Saturday is due to be sunny 13 degree peak so I've turned the storage off and will see what the house temps do. Hopefully the sun room will get up to around 26 and we take some of that heat into the main house.

We started with the heating in November and its still on this month so we're closer to half the year. Hopefully we'll cut this as sort out the place. I do need to do some sums on ESHP and see what the scop would be if it draws from outside. Not sure how to calculate the heat reduction if draws from internal. I know that they can integrate with pv but not sure how using off peak eco 7 would work.

I think my water use figures are probably a bit high. Current worst case, two short shower (5 mins) , maybe two basins of water for dishes and a bucket or two if hot water if the floors are getting washed. The bathroom remodel is going to bring in a replacement bath (deep soaking tub) that can take about 200 litres. It's a luxury but our current bath is bigger and needs so much water that it's never used. I miss a soak.

Thanks for that info. Sounds like that could fit my needs. I'm probably being daft but on a sunny day I'm thinking the E7 would have got the tank to temp overnight and the solar would purely be doing top up of heat losses. In such a situation I'm guessing that I need to be monitoring the weather and then deciding if I want any water being heated overnight.

Two people in the building. Occasional overnight visitors. 2 bedrooms. Good size unobstructed South facing pitched roof. I estimate 5x3 would be suitable for panels. Google tells me 1216 sun hours in Glasgow.

Sounds like a simple one solution stop. I do wonder though on a sunny day (they happen more frequently in Glasgow than advertised), we'd probably have the ability to heat more water. We need to assume daily forecast of grey and miserable and would therefore be heating the tank to required temp on overnight eco 7 rate. This is where my thinking on some 2ndary tank comes from. Temp sensors and some automation might help here. Standard tank temp of 50 (or whatever is a healthy hot water store temp) unless the pv is kicking in, in which case ramp the water temp up. Some type of temp regulator on outlets involved which may or may not exist as standard.

Thanks. That's interesting. No header tank required with this setup?

I have another thread relating to heating that I'd gone a bit off topic into DHW so thought I'd start something in the right spot to request advise and opinion. Current setup : immersion. Probably 20 plus years old. Not easily accessible to insulate further. Very little control - we added a timer to reduce energy use Wired to economy 7 only so no mechanism to top up outside eco 7 hours. Mains Flow rate - 1 ltr every 2.5 seconds Pressure - not known at the moment Useage ltr - max 300-400 per day. Average 200 Wish list Reduce /remove attic headers to make the attic space one day habitable Easy control / adjustment of when the water is heated and to what temp on any day Ability to top up outside of eco 7 hours Pv ready. One day we'll get this in and I don't want to rework what we put in now Energy storage (as hot water). No battery as its not yet financially viable. Any spare pv we'd want to use to heat water and store. Faster delivery of hot water than the current 2 mins lead time Low maintenance system Constraints No mains gas Plan to heat house with A2a and avoid any wet system install. Basically ASHP discounted. Systems considered ESHP - not convinced on this taking heat from the house but could have potential gains even if draw /exhaust from outside. Header tanks not required. Fast delivery of hot water. Not cheap. Potential maintenance. Could be very cost efficient running over eco 7 hours only (if possible) . New immersion - doesn't remove the header tanks. Cheap. Reliable. Not sure how this integrates with pv. Slow delivery of hot water. UVC - removes need for header tanks if I'm understanding correctly. Not sure how this integrates with pv. Gives faster delivery of hot water? Price ranges vary but cheaper than eshp. Suffering from paralysis by analysis and lack of expertise to make any real sense of any analysis I do! On the plus side, I'm not alone as two of the companies I've spoken to about DHW systems were astoundingly less knowledgeable than me. That does leave me seeking out the collective build hub hive mind for advice. I think to benifit from a future pv install I might need to combine systems so there is ability to have hot water on demand but also ability to store hot water (feed to the main water heating system?). Is that total nonsense and I've missed a simple solution? Any input appreciated.

Mirrors my experience. On a cold sunny day once the sun room temperature is above the lounge, the doors get opened and the lounge will generally climb up. Even on a cold day (5 degrees outside last week), the sun room hit 24 and that brought the lounge & kitchen up by 3 degrees. If only I could pipe that heat to the baltic north facing room. To avoid energy waste, we simply don't open up the sun room when it would leach heat from the house. It still benifits the rooms its build off as it's generally at worst 4 degrees warmer than outside temps.

@Furnacewent with Senior Architectural Systems Pure. I think acoustic performance is a bit like u value in that you need to consider both the glass and the frame but someone more knowledgeable that me will hopefully confirm if I'm talking nonsense or not. Overall we were given a figure of 39 dB and u Value . 95. The other thing that comes to mind purely based on my experience is I specified no trickle vents. Didn't want any more ventilation than we already have. Was reminded it would be a sell on issue without alternative ventilation installed but in my limited experience, trickle vents were assumed unless you specified otherwise.

Triple. I assumed the same but looking retrospectively there are DGs that give the similar values to my TG and alternative TG that have better acoustic performance. They are a vast improvement on our previous but I think I expected better and should put more weight on that requirement as we're near a busy road and have loads of seriously noisy birds nesting in the hedge!

I'd add any acoustic requirements to the list and get the acoustic performance included in any quotes. I didn't pay enough attention to that and it's the one thing that irks me post install.

Last month we probably had at least 7 days where the temperature in there was over 20. Doesn't take much sun for the temperature to climb quickly. It will get any sun unobstructed morning through to early evening.

Where the sun is cracking the slabs today! I expect a sun room temperature of 26 degrees by 11 am.

Air to Air system heat pump (outdoor) and indoor air conditioning unit(s). We're in the process of getting quotes to use a2a for home heating with the added benifit of ability to cool in summer. Our sun room overheats even in winter direct sunlight The models we're looking at are stating COP of 5. Tied into PV that could be very cost efficient without having to change your designs.

Hear say. 100%.😁 As I say, we're new to this all but have taken advice of long term septic tank users and the local company that service and desludge. I'd go with the science but I'm light on the exact workings.

We're STP and new to that system having only moved here last year. We requested inspection report and sesludge before moving in. The company that conducted (who seem to be well regarded) told us deslugde every two years and they check they system at the same time. I assume time frames might differ based on tank size /occupancy - the previous owner was doing every three years. As others have said - never empty. Takes some time to build up the right conditions for optimal operation.