An electric boiler is never going to deliver more energy then the energy you put in to it (in the form of electricity). A heath pump can because it extracts heath from the air (or better said the water in the air).

Now if this were in France with a modern grid and nuclear power it might stand a chance. But the UK with it's aging grid and aging power plants? I doubt it.

We need the "hybrid car" of boilers right now I think.

Jumping from gas to ASHP is too big a hurdle for most as it involves many changes (upgrades in electricity, insulation systems, radiator upgrades and/or redoing the floor with underfloor heating).

I think an immediate, gradual, cheaper solution would be boilers being run on biofuel.

Isn't ZEB just an evolution of storage heater? https://en.wikipedia.org/wiki/Storage_heater

They are several times less efficient than heat pumps.

> Inappropriate for many (possibly most) dwellings in the UK

Why ? UK is well above freezing (and even them, heat pumps _work_ below freezing, even with a COP > 1). So I'm curious about your assumption

The problem is at least partly because people in the UK are enamoured with old houses to the point of detriment when it comes to things like thermal efficiency. There are all sorts of heritage laws, local "conservation areas" etc that forbid things like double glazing, modern insulation, etc. The quality of the typical housing stock here is very poor.

My understanding (and I'd love to be wrong here because it annoys me that I can't take advantage of high efficiency systems) is that:

1. Existing UK homes use radiators that would need to be replaced with larger radiators with an air-to-water heat pump, due to the water not being as hot as a traditional radiator system. Some of this is cost (replacing radiators), some of this is simply not having the space - many radiators are installed below windows so there isn't much scope to increase their size

2. Replacing radiators with an air-to-air system in each room is too expensive (especially since older homes often use solid brick/concrete for internal walls), as well as a large number of terraced houses with limited space for external piping/units.

3. Our mild climate (as well as housing stock age -- and, I'm betting, good historical access to local fossil fuels) means UK homes are very poorly insulated, and with our humid climate can have humidity + mould issues if retrofitted with insulation that reduces drafts.

The radiator upsizing makes sense, but there also exists high temperature heat pumps (~70C) that work with "old" radiators

Yes. The other issue in terms of housing stock is that a lot of the more recent housing stock has nowhere to put a cylinder for hot water, which means it's not practical to use HPs for hot water for showers etc. This either means replacing showers with instantaneous resistive heating-based "power" showers or keeping two systems even if you can retrofit with an air to air HP for space heating - adding cost and reducing savings available.

But the biggest barrier is the relative cost of gas vs electricity in the UK. Gas is about 4x cheaper than electricity per kWh so even with a COP of 4 the efficiency savings will take a long time to pay back capital cost.

Most boilers sit in peoples homes. An ASHP sits outside and you will need at least 5sq meters of space with excellent ventilation. That excludes many people (including me).

But even then during winter the average ASHP makes too much noise. Planning regulations are starting to recognise the fact that they can be a nuisance in semi-rural areas, and your neighbours will hate you.

This ignores all the problems around having to retro-fit larger radiators in older homes due to lower flow temperatures.

I don't know what you folks are able to choose from, but my neighbors have one of those installed last year and I can't hear it. So my guess is that noise is an old story which keeps being told - unless old models is all one can get.

> you will need at least 5sq meters of space with excellent ventilation

I don't see where you read that, but at least for Daikin ones, the front must be clear, but usage can be shared (eg. a driveway)

The OP did a bad job but here are my guesses.

Most traditional UK homes do not have central air, they use boiler/radiator systems for the winter. Retrofitting these homes do have central air with a heat pump probably does not make sense.

I don't think the product the OP linked was a very good example either. It's just an electric boiler that somehow stores offpeak energy to be used during the day. Don't know a lot about boiler systems but I cannot imagine these are that revolutionary and there are other similar systems out there, it is just an electric boiler with a smart energy/battery storage system to capture the off peak energy...seems like you could do something similar with a standalone electric boiler and a battery backup system.

Thermal storage bricks are a lot cheaper than batteries and chargers. The bad part is that it's resistance heating, which throws away a lot of exergy.

Agreed! I just said battery to cover any type of energy storage mechanism.

Heat pumps work perfectly fine with radiator systems.

They do indeed, same with heat pump style water heaters used in America.

Can you link a drop-in heat pump replacement for my Vaillant gas boiler mounted in tiny apartment bathroom, which heats the radiators in the winter but also provides hot water year-round?

Yes. For example Daikin Altherma, but I'm sure that every brand has a compatible system

It seems like it requires an external unit. I cannot easily mount an external unit. The bathroom is far from external walls, boiler is connected to the shared air intake in the wall that leads to the roof. So this doesn't look like a drop-in replacement.

Outdoor units are pretty flexible in the sorts of places they can be mounted and the insulated refrigerant lines can be run to the interior of buildings fairly easily. Don't just assume a solution can't work until an expert says no.

And even if you can't hook into your existing radiators wall mounted mini splits don't require extensive interior changes to function (plus you get cooling as well)

I do have a mini-split AC which can also provide heat. It is OK for autumn and spring but it is a no match for a radiator heating when it's really cold outside in the winter. Yes, of course I can run the lines through the whole apartment but this is a much costlier proposition.

Talk to your local gas/water/heating instalation company, they are the experts.

No, that isn't accurate. Air to water heat pump systems can be incredibly efficient and effective, even if the insulation isn't great. Flow temperatures are usually lower than gas boilers, so sometimes radiators need to be upgraded to larger ones but with a good quality heat pump and proper setup (weather compensation being a big one) there actually are few problems.

There is a huge education gap unfortunately, since there are grants to install them so you get dodgy installers doing crap jobs. Even with a high quality heat pump, if it's not set up correctly you can get COPs as low as 2.5 or so and pay more than having gas. There are some good channels on YouTube of people with the proper training making fairly minor changes to these systems and acheiving SCOPs around 4 which is cheaper than gas.

I think you are replying to the wrong thread? I never argued that they would never work, I am a big proponent of heat pumps. Just taking a stab at why the OP thinks they are not good for UK. Retrofitting older UK homes probably takes more steps than what the government grants are providing.

Thanks for the information though.

I expect it's more to do with how poorly insulated most UK homes are

Insulation and having outdoor space to put the thing without sacrificing half your garden.

Read the first line of the article, it specifically references an air source heat pump.

The-ZEB are very thin on the details, is there a technical description of how it works?

Purly heating by energy is the worst case scenario.

I have to believe your 'the zeb' system has to be a scam as the energy amount such a small device can store, doesn't add up at all.

If it requires a big water heating tank, than this device should be as big as a computer + a heating coil.

Whatever they do with there 'energy core' its either magic and patented or just a scam.