Electric combi boilers / solar panels / eco heating solutions

Octopus ASHP woes continued

Apparently a structural engineer report/survey is needed to install the unvented cylinder (200L capacity + 50kg) in the airing cupboard, which currently has a 140 litre vented one

Got this assessed (after the first visit I had to remove a board and cut off some plasterboard to gain access and the guy dropped by the next day again) and looks like the cupboard needs strengthtening before any more load can be put in. It's hard to do with the current tank in-situ (the eng described how it should be done in the report, but also added it might not be practical due how confined the space is) so I'll ask if Octopus can do it after draining the system and taking the old tank off, first day of the install. Essentially rebuilding it with much better access.

About £520 in so far (PP fee, structural eng + extra asbestos report) but in the meantime I should line up another combi survey -- BG came in about £4k but can't reuse my beloved tado.

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How have your running costs been affected by the recent cold snap?

Is your ASHP running during the ‘expensive’ periods? I’m assuming your system is set to heat the hot water during the cheap periods.

Do you have Tado and Homely working together? How does that work?

About £520 in so far (PP fee, structural eng + extra asbestos report) but in the meantime I should line up another combi survey -- BG came in about £4k but can't reuse my beloved tado.

Got new quotes for few 35kw combi options, looks like the scales are tipping that way (cheapest is a Glow-worm). The plumber/installer (which seems nice and capable) also clocked the gas pipe needing an upgrade (straightforward run) which is something the BG video survey unsuprisingly missed. Will need an updated Tado EU/eBus receiver that I'll need to sort out in the meantime.

On topic: I'll quickly contact Octo sometime next week to cancel, also try my chances getting that £270 I paid for the PP (which hasn't progressed at all) back.

Peaked at almost a tenner for the coldest day, usually less than a fiver, that’s for all electricity, heating & HW.

Ditched the Tado along with the gas, ASHP is controlled by Homely and we’re on Agile Octopus so it tries to only run durning the cheapest periods, which means overnight basically. It’s quite loud tbh, in the dead of night. I’m getting used to it and there’s been no complaints from neighbours so I guess it’s fine.

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Thank you, very interesting.

So are you not zoning the house with smart TRVs on the rads anymore? We're getting a Vaillant ASHP, mainly due to noise (went to visit someone with the same 7kW model we're getting, it's much quieter than the Daikin and Mitsubishis I've experienced) but it's not compatible with Homely currently, so looking to use Tado TRVs for the rads...

Heat Geeks seem to think the Vaillant controller is pretty good so you might not need Homely anyway. From what I can work out, with decent control firmware you could basically do what Homely does by setting schedules.

We’ve got dumb TRVs on all the bedroom rads but apart from our bedroom they’re all set to max. Seems to work fine if the rads are appropriately sized based on a heat loss survey. In general, you don’t want to restrict flow so open valves and correct sizing is the way. Feel like we got there by luck mostly but it seems to work.

Advice needed - we need to replace the boiler in our 1920s (not v well insulated) semi.

All plumbers we've spoken to say we replace with gas at this stage and from a pure usability perspective we probably want an invented cylinder.

I don't think we have money to insulate the whole house well enough to go heat pump at this stage, but I don't want to shell out a tonne and make it more difficult to do that in the future - if we go with the plumbers recco and put an unvented cylinder in the loft, is this going to make it a massive pain to sub in a heat pump later? I guess yes, but what is the alternative if the building is too leaky for a heat pump to really work at the moment?

You need an unvented cylinder for hot water with a HP so you’re not wasting any money getting one now. Just make sure it’s big enough to store water at 45 degrees and meet your household needs.

Exactly what I needed to hear, cheers!

Now to work out what "big enough" means...

That’s a tricky one.

180l @ 45 degrees does two consecutive showers for us, 6 to 8l a min.

There’s a government white paper on cylinder sizes for HPs but tbh I’d just go big. Oh and make sure it’s specced for HPs, they need a bigger surface area of pipe inside. Ours is 3m2 I think.

Yep agree go big seems worthwhile...

The only other thing I'm thinking is pipe size from heat pump - seems to be larger bore than typical heating pumps so will need to work out how it gets from where the pump would be to the cylinder (or at least, think about access when we decide where to put the cylinder)

Thank you, this is the route we’re being drawn to also.

Just going to use the Vaillant controller with weather compensation, and dumb TRVs.

I would really reconsider splurging for a gas boiler right now.

Even if your house is poorly insulated and leaky, a heat pump will work as long as you beef up your radiators. Friends of ours got a Mitsubishi Ecodan ASHP ~3 years ago, in an un-refurbed Victorian terrace with single-glazed dash windows and no insulation. All they did was upgrade the rads. Their bills were equivalent to those with their previous gas boiler, factoring in no more gas standing charges, Octopus smart tariff and smart controller programming.

They’ve now put in triple-glazing, UFH on ground floor and some insulation, and their bills are ~30% lower.

The £7.5K ASHP grant now means you’ll pay around the same price as a new gas boiler install, future proof yourself, and ur farts will smell delightful. It’s a no-brainer as far as I’m concerned.

I'm just not sure it's that simple - I'd need somewhere for the pump to go, plus I think leaky semi will be worse than terrace (one more exterior wall), and upgrading rads won't be cheap itself - we have what, 10 across the house, and they're all big? Plus pipework is relatively narrow stuff so I may need to upgrade that between the rads too.

I don't want to rule it out but I don't really buy the idea it won't be a lot more expensive to make it work adequately

The £7.5K ASHP grant now means you’ll pay around the same price as a new gas boiler install

I'm assuming that's not counting fitting 10 new bigger radiators though (and whatever changes are required to fit those).

Although the biggest problem for me at the moment is how big they are if you have limited outside space.

Agreed on the form factor front. The UK is still in the stone age with regards to product availability and install/support infrastructure. In Scandinavia for example, many low-rise single-occupancy dwellings have heat pumps that look like chode chimneys up on their roofs, tucked out the way, with the cold exhaust venting harmlessly upwards.

This form factor doesn’t exist in the UK, although the new Red/Octopus ASHP edges closer to something a bit more palatable than a massive, ugly grey aircon box blowing icy air across your patio.

upgrading rads won't be cheap itself - we have what, 10 across the house, and they're all big

The quote includes rad swaps and the rads itself. For me upgrading 10 of the 14 rads the quote was ~£3,200. There were extra costs though, another asbestos test (~£100), a structural survey (~£200, which yielded bad results), planning permission (~£270) and I still need to get a chimney blocked. So it will add up to £4000 if we go ahead (still waiting more info from Octo guys, as they want to see what really they can do to make it right about that bad structual survey, before me cancelling the install. I don't want to involve another trade to fix that but I'm happy to pay Octo to get it fixed, assuming it would be at a reasonable cost)

In comparison to that, a new boiler install quote came at £4,500 (including a gas-pipe upgrade) very straightforward, no headaches. But is it really what to go for in 2024? (I'm now waiting to see if it's possible to go with the ASHP install...)

BTW recently tried BritishGas for the HP and the auto-quote (subject to survey) came in at £10k after the grant. Needless to say I didn't book the survey.

If I can afford the HP I will go with that, if not, the old creaky boiler remains for now until I'm fed up with the vented tank.

Heatgeeks is another option to get a quote from, they now have a heatpump specific tariff partnered with ovo and are about to launch an industry first CoP guarantee on thier installs, they were quoting 4k more than octopus for me though

Make sure to check out small, independent local MCS certified ASHP installers, who will come close to the big energy supplier quotes without the long lead times.

Flipping this process and upgrading the building fabric first and the buying the ASHP later would've resulted in a better outcome/more savings, no?

Gas standing charge is 30p a day, or £11o a year. The bills would've lowered by 30% by, so on the cautious side: 10,000 kWh * 30% * 25p per kWh = £750 a year by doing the building fabric upgrades first.

ASHP will become cheaper/better over the years (Octopus Red, etc). Getting the timing right by still switching towards the end of the ASHP incentives would be the ideal option.

For sure, fabric-first always…

But if you need a new heating system now regardless, then with ASHP including BUS grant being at price parity with a boiler system, it’s an easy choice in my eyes.

Fabric upgrades are invariably disruptive, and you can plod along running an ASHP at 55deg flow temps without them for a bit. Fitting a £4K boiler system now with a view to ‘upgrading’ to ASHP down the line doesn’t make sense to me. You might as well put the £4K towards your leccy bills until you’re ready to insulate.

Octopus are offering £1000 off solar orders placed in January. Just got off the phone they were very helpful, but ‘cos of my weird shaped roof, they couldn’t help - need to get minimum 4 panels together.

Can anyone weigh in on this setup I’ve had from a local firm?

6 or possibly 7 435W panels
Solaredge inverter and optimiser

I’m not sure the easterly facing panel is worth much, but will this work in general. Does the solaredge inverter get around the fact that I’ve got single panels which won’t produce much on their own, minimum voltages and all that.

Would be interested to know if anyone thinks there are some key questions to put to the supplier. Cheers.

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If that single panel is facing east, aren’t the others facing north…?

No, north is the top of the image. Edited to add blue along main roof ridges.

So the single panel faces west no?