Sunamp Thermino in 2025?

[Workerbee]

Hello! What are people's feelings about the Sunamp Thermino in 2025? I've read every discussion thread I can find, including a few excellent detailed ones on this forum; however, many of them seem to be from a few years ago and I couldn't find much recent discussion; and given this is a rapidly emerging technology I thought it might be worth revisiting.

 

The main benefit is size; there are others, but that's the key one. On the other hand, many of the threads mentioned issues with customer service, and reliability. Towards the end of several threads I got the impression some of the reliability issues were to do with early models, and firmware updates and newer versions had solved them. Is this the case, and has the customer service improved, too?

 

Any thoughts greatly appreciated!

[JohnMo]

Have you seen recent threads? Several failures, wouldn't touch them with a barge pole.

 

Pretty rubbish for a heat pump as it requires heat pump running at high temperature for the whole heating cycle.

 

Just get an unvented cylinder - tried, tested, cheap, installer friendly. Does the wheel need to be reinvented? No

[Workerbee]

Thanks @JohnMo - no, I couldn't seem to find much beyond about 2023. I got the impression from the threads I'd read that most of the issues (leakages, charging only after dropping below 50%, etc) were mainly from early models. 

 

I'm an all-electric house, so I'm looking at the direct version (Thermino ePlus). The size and shape is the main attraction for me, as I could stick it in a cupboard. In terms of a direct unvented cylinder, I could find a way to fit one in if I had to, but it's not ideal. Finding an installer isn't straightforward, either; of the 5 or so I've had around, two didn't bother quoting, two were expensive to the point the Sunamp is the cheaper option, and one was suspiciously cheap. 

[nod]

I spoke to a couple of HP installers 

regarding Sunamp Both had the same views as John 

[Workerbee]

Thanks @nod - what was the issue the installers had with them?

[nod]

5 minutes ago, Workerbee said:

Thanks @nod - what was the issue the installers had with them?

They both said unreliable and outdated 

[Nickfromwales]

16 hours ago, Workerbee said:

two were expensive to the point the Sunamp is the cheaper option

Erm….how much were you quoted for an UVC to be installed??

 

Sunamp / Thermino’s supplied and fitted are absolutely insane money. Spoke to a guy the other day who got billed £7k for a 9 (210) unit. 

[Nickfromwales]

16 hours ago, Workerbee said:

I got the impression from the threads I'd read that most of the issues (leakages, charging only after dropping below 50%, etc) were mainly from early models. 

I fitted 3 of the earlier units in one large multi-bathroom etc (£4m) house and they just dropped like flies.

 

SA changed them for the “new and improved” unit, and they then snuffed it one at a time. Terrible build quality, you’ll find pics I posted on here.

 

I worked directly for SA for a couple of years, and my sole purpose was going to disgruntled clients to be shouted at because of the lack of communication etc. As the fella in charge is a social media hog it appears people on BuildHub get suspiciously good levels of service, but that’s not been the case offline I assure you, in my direct experience. 
 

One client got refused an exchange as they said it was a ‘non standard’ installation, the laugh was that they approved my design prior to them going in, ffs 🤦‍♂️

 

The only true measure you can really get of these is by speaking to installers (who want the kill) or reading here (and not realising it is pure marketing BS that they react immediately and “go the extra mile”).

 

They didn’t for a poor lady who was washing her hair in the kitchen sink for 13 weeks…….

[Workerbee]

11 hours ago, Nickfromwales said:

Erm….how much were you quoted for an UVC to be installed??

One was £2230, and the other was £3600. This is for a direct uvc (I think one was 170l gledhill, the other was unspecified) and pipework. Two others didn't turn up, another wanted to charge to quote, and the sixth offered to do it for £250 labour if I piped up to the cylinder (which is what I requested, to keep costs down). At that price, I wonder what he'd be like. Alternatively, I can get a 210 directly heated sunamp for £2k and fit it myself. Coupled with having a small property where space is an issue, the sunamp seemed a great solution in theory.

Thank you for sharing your experience, @Nickfromwales - very useful. I'd read your comments on a previous thread when I was researching. It would be a great shame if quality and service hasn't improved.

[JohnMo]

7 hours ago, Workerbee said:

sixth offered to do it for £250 labour

That's a good price, make sure he has the G3 certificate. Once the pipes are at the cylinder, which is job from the sounds of it there really isn't that much to do piping wise.

 

Is this new build or retrofit? What are you doing with cold water going the taps, is that coming from the cylinder multibloc control valve?

 

If not you need to plan a pressure regulator valve where the water comes in to the property after the stop cock, so hot and cold pressure stays in balance. If going that route you also need a check valve at the hot water outlet from the cylinder.

 

Isn't a 210L cylinder pretty big for a direct cylinder where you can easily heat to 70+ degs?

 

 

 

[Workerbee]

Thank you @JohnMo - yes, £250 seems very cheap, which made me question it. Rough prices on text message rather than a formal quotation make me nervous! My fear would be deciding on a uvc over the sunamp then finding I can no longer get hold of him when the time came. 

 

The 210 was the sunamp size (uvc litre equivalent); the next one down is 150, and with potentially 4 showers a day from a powerful shower, I thought I should play it safe. If going with a uvc I was thinking of a 180l. I'd probably go with the multibloc solution. 

 

On paper, the sunamp is the much better solution for me both in size and price, so it's very sad that it's let down by reliability and customer service. I could forgive the former if the latter was excellent. That's why I wondered if anyone had had experience in the last year or so in the hope that things had improved, as much of the online discussion is from 2023 or earlier.

[Russdl]

@Workerbee  

 

Not recent experience as such, we’ve had our Sunamp UniQ eHW 12 up and running for about four and a half years. A thermistor string failed shortly after it was commissioned and that was promptly replaced.

 

Other than that it just sits there quietly doing its thing. If we suffer a major failure in the future (which I guess must be on the cards) I’m pretty sure we’d get another one. 

 

There was/is clearly a risk being an early adopter with any new technology but it was a risk we were comfortable to take. The arguments ‘for’ are thin and there are plenty of arguments ‘against’ on here but we’re still firmly in the ‘for’ camp. 

[Workerbee]

Thank you for that, @Russdl. Do you find the flow rate is as good as a uvc? Sunamp mentions main pressure hot water but nothing about flow rate, and I wondered if it might get restricted in order to maintain temperature, particularly when the incoming mains temperature drops in winter. I'm keen to have a decent shower experience!

[Russdl]

The flow rate at the shower is around 12 l/min, the incoming mains supply is 15 l/min (and 3bar).
I can’t compare it to an UVC as we’ve only had a Sunamp in this house.
 

We have two showers and when they both run at the same time there is perhaps a small drop in flow but if you didn’t know you wouldn’t know. 
 

We have an accumulator that helps when both showers are running as our mains supply is a bit meagre. 

[DamonHD]

For the record our Thermino is doing just fine, helping us soak up solar PV in the middle of the day in particular and reducing how much DHW we need from the heat pump.

 

https://www.earth.org.uk/note-on-solar-DHW-for-16WW-UniQ-and-PV-diversion.html

 

An alternative these days is to have (more) electric/mains battery along with the heat pump to act as a store.

Edited September 2 by DamonHD

[Workerbee]

Thank you everyone - it's been very useful hearing your experiences and knowledge. 

 

I've continued my research (ie put off making a decision); leaving aside the customer service question for now, I've got a list of pros and cons for the Sunamp vs uvc, which I can post if it might be of use to anyone in future.

 

But one thought occurred which might swing it decisively in the uvc's favour, and it's that you can 'overcharge' a uvc - ie increase the capacity by keeping it at a higher temperature, which you can't with the Sunamp.

I'm thinking of the Sunamp eplus (direct) 210 - ie Sunamp say it's equivalent to a 212l cylinder. Mixed down to 40 degrees with an assumed 10 degree cold feed, it produces 301l according to the tech specs. (footnote: is this right? It would imply a temperature directly out of the Sunamp of only around 53 degrees).

 

The only thing I need dhw for (other than hand washing) is a shower. My showers are about 8 mins, my partner about 14 mins. 22 mins total. Assuming a 12lpm shower, that's 22 * 12 = 264l. If I get a great shower experience at 15lpm, that's 22 * 15 = 330. Either way, it doesn't leave me much wriggle room. I would then be relying on a rapid recharge time with on-peak prices, and if we had guests, we're stuck. In winter, even more so. But with a 210l uvc, I could heat it above 70 degrees and get more water volume. Am I missing something? 

 

[SteamyTea]

5 hours ago, Workerbee said:

Am I missing something? 

Not really, it is what I do when I have guests.

One thing to check is that there is not a thermal cutout at 65°C on the immersion thermostat.

[DamonHD]

I 'fill' my Thermino to ~80C which adds ~30% to the nominal capacity over the phase-change temperature.

[Nickfromwales]

1 hour ago, DamonHD said:

I 'fill' my Thermino to ~80C which adds ~30% to the nominal capacity over the phase-change temperature.

The phase change is 58°C, so if you are close to that the recharge time is stupidly elongated. 
 

You have to put ~80°C into one of these units to get it to reheat quickly.

 

I fitted a pair of ‘9’s’ to a buffer fed from a log gasification boiler, and until the buffer (thermal store) got up to north of 75°C the Sunamps didn’t really pick up very quickly. 
 

 

I hadn’t finished fitting the insulation at this point!! Relax people   

At 82°C they seemed to then get some sense of urgency.

 

An UVC would have started mopping up useful energy way sooner <60°C. 

[DamonHD]

I'm heating by diversion so that doesn't apply.

[Nickfromwales]

14 hours ago, DamonHD said:

I'm heating by diversion so that doesn't apply.

Irrespective, the in-built controller decides at what point the thermostatic control will say that it can or cannot accept further input. You don’t get to choose to ‘put energy in’, you just do so until it is satisfied.
 

To ‘fill’ your thermino to 80° you just need to connect power to it and walk away. It’ll shut off when the thermister string feeds info back to the PCB to say it’s PCM (58) is heat saturated. 

 

The heat (input energy) is either by external source (which you have to govern its max temp) or by its own in built direct electric immersion element. It is this that decides the recovery time, the amount of heat input, and not any person.

 

There isn’t any ability to be its boss, and decide what to ‘give it’, there’s just an inbuilt control which is satisfied or not. If not, it’ll ask for more heat energy, and you supply it or you don’t. If you don’t, it’ll simply go to bed hungry.

 

One of the worst things ever, to try and give to a simple member of the public and try to explain the behaviour of a PCM based device. Ask me how I know.

[Workerbee]

I'm looking at the direct, electric heated sunamp model as I'm an all electric house. So does this mean I was right in thinking the sunamp can't be 'overcharged' to increase its storage like a direct uvc can be? 

 

I'd been looking at the 210 version because I thought it would be overkill for two people; it's sometimes quoted for 6 person houses. But if my back-of-fag-packet sums were right, then even a 210 wouldn't be enough. Only an 'overcharged' - or at least above 55 degrees - uvc would do it, with the additional benefit of a second immersion if a boost was needed. As @SteamyTeasays, though, I'd need to check for thermal cutouts.

[DamonHD]

8 hours ago, Nickfromwales said:

Irrespective, the in-built controller decides at what point the thermostatic control will say that it can or cannot accept further input. You don’t get to choose to ‘put energy in’, you just do so until it is satisfied.
 

To ‘fill’ your thermino to 80° you just need to connect power to it and walk away. It’ll shut off when the thermister string feeds info back to the PCB to say it’s PCM (58) is heat saturated. 

 

The heat (input energy) is either by external source (which you have to govern its max temp) or by its own in built direct electric immersion element. It is this that decides the recovery time, the amount of heat input, and not any person.

 

There isn’t any ability to be its boss, and decide what to ‘give it’, there’s just an inbuilt control which is satisfied or not. If not, it’ll ask for more heat energy, and you supply it or you don’t. If you don’t, it’ll simply go to bed hungry.

 

Not true for me.

 

Via tight control using my Eddi, I regulate how full I let my Thermino get and choose whether to let it get full enough for its automatc cut-out to operate or not, which enables me to do things like this to reduce our grid exports around solar noon to be kinder to the grid:

 

Full-week 15-minute con consumption and net imports for 2025-07 generated with sh script/storesim/load_profile.sh 202507.

Full-week gross consumption and net grid flows for 2025-07. Times UTC. Data and other views are available.

 

And there is about 30% heat capacity above the 58C point before that cut-out.

[JohnMo]

6 hours ago, DamonHD said:

Thermino

You obviously have solar and an ASHP, does it make sense to faff about diverting electric at a CoP of 1, when you can export and heat cylinder at CoP of 3 to 5 depending on setup and outside temperature. Wasting export income and giving the local grid very green energy?

[DamonHD]

Yes, I believe it does even now, eg the Thermino loses heat at half the speed of the DHW cylinder even when much hotter, and at a rate comparable to the electrical batteries' self-discharge.

 

I had the Thermino+Intasol long before I installed the ASHP.  Given the rapidly falling price of electric batteries now cf when I started it would now make sense to consider additional electric battery (in particular to be able to cover the maximum power demand of the heat pump) instead of heat battery for new installations.

Edited Wednesday at 14:06 by DamonHD