Do you heat your home (or, business etc) by using a heat pump alongside ‘regular’ electric heating (ie, resistive)? Maybe, heat pump plus a few strategically-placed storage heaters? Or, heat pump plus solar pre-heating of warm-water immersion cylinder?
We’re considering a switch to a heat pump at some point (instead of current gas boiler.) However I doubt we could get the house all the way to heat-pump readiness; so, I’ve considered a hybrid approach… It’s a standard semi-detached house, good loft insulation, recent cavity-wall insulation (which seems of reasonable workmanship), underfloor insulation (Elastospray); also, 2.4kW of solar PV on the roof.
Thanks for any comments on such experiences.
If you aren’t going for the BUS grant you could keep your boiler as backup and install a heat pump into the same system. A kind of DIY hybrid system.
Apart from that I know of several people with other concoctions of “hybrid”. There are storage heaters and freestanding air to air heat pumps. Also two air to water heat pumps in the same house, one for hot water and the other for space heating. Each heat pump selected to run in its optimal range.
All the owners are happy with their solutions.
A well sized heat pump does not necessarily provide all heat requirements at all times. This is particularly true where your property is exposed to extremes of temperature. Sizing a system for extreme cases can lead to fitting a larger heat pump than is normally required, leading to higher up front costs and inefficiency in normal use. Far better to have a slightly undersized system and add extra heat when required.
1 Like
Thanks Tim, sounds fairly positive. We’d definitely be going for BUS! Think it would have to be air-to-water HP, with something in addition to aid space heating if hot water demand went up. Presumably an immersion cylinder for HP-heated water can also have a (resistive) electric element in it, for topping-up?
Unless you have a high temperature heat pump you will need an immersion heater for the anti-Legionella cycle, so all dedicated heat pump cylinders have them.
I have solar thermal too, so I would need a dual cylinder. Such things are available.
1 Like
This is a good point. An air to water heat pump cannot heat domestic hot water and space heating simultaneously, so the house will start cooling while you heat the water. The poorer your home’s heat retention the more critical this is. Hence my example above with two heat pumps, one for each.
I seem to think there is a potential grid capacity issue with this, as we will all want to top up the heat with direct electric heaters, whether storage or otherwise, all together at the same time, namely in the coldest spells of weather. So the grid has to provide much greater capacity to cope with these periods, which is a lot of cost to cope with these short periods of time. So direct electric top-up heating is a good and inexpensive strategy in the short term for individual houses but a poor strategy nationally and for the planet if more of us were to go that way. Thus my thought about this is that, in the longer term, a less carbon-expensive strategy nationally would be (perhaps counter-intuitively) for us to have bottled gas waffle heaters for those cold snaps, probably of the portable variety, which can be stored out of the way for the rest of the year, making sure that we have good enough ventilation to remove the products of their combustion for the relatively few days per year when we use them. In the meantime, however, low-capital-cost direct electric heating is an attractive alternative for our household when we have visitors, and when we don’t we will apply extra jumpers and run on the spot for a minute or so every half hour.
1 Like
This is quite true in relation to the mass installation of heat pumps but the grid capacity would still be a lot less than if everyone got resistive heating.
Yes, if everyone had purely resistive heating for all their heating needs, and no heat pumps, then a hugely bigger grid would be needed. Maybe I didn’t explain it well, but my thought is that bottled gas might be the best form of heating for us all to use to top up our slightly undersized heat pumps in the cold snaps, thus avoiding the need for the nation to have a grid large enough for us all to briefly use resistive electric heating, just for that topping up, all at the same times, namely in the cold snaps.
For the Boiler Upgrade Scheme, is a slightly undersized heat pump allowed, I wonder?
I hate to think that even medium term it is acceptable to burn anything but I get your point.
With changes to ocean currents there is a risk of loosing the Gulf Stream. We will then be subject to much more severe winters as a regular occurrence. Unfortunately the government’s plans for climate tolerance/adaptation have hardly started being considered.
1 Like
Mine was designed, via the Heat Geek umbrella, for a target internal temperature of 18 degrees, so that I didn’t end up with an oversized heat pump.
MCS didn’t have a problem with that, and the BUS grant has been paid.
I am hoping to keep the house at 19, and prepared to top up the heating on cold winter days with direct electric heaters if required.
If I upgrade windows and/or add more insulation, then top up heating is less likely to be needed, and the heat pump will still be far more efficient than if I’d got a bigger one. The heat pump has only been in for nearly 3 months, so time will tell whether I made the right decision.
2 Likes
I look forward to learning about your heat pump journey, perhaps in a new thread.
As the system is Heat Geek I presume it has weather compensation set up and no buffer tank.
1 Like
@mike_killian, have you progressed with your heat pump plan/dream?
I hope this thread has helped you decide on the best action for you. If you have got to the quotes stage you will probably have met a wall on incomprehension when it comes to the various hybrid options. I was lucky to find a fairly local installer that accepted my figures and fitted a heat pump that was correctly sized not just for the house but for my usage.
As @sianrichards55 has also done so, it shows that perseverance can pay off.
1 Like
Should have also said that heatloss was calculated on the assumption that the ground floor was about to be insulated. This hasn’t happened yet, although much of the flooring has been lifted in readiness and so my current heatloss is greater than that calculated.
Yes, I do intend to write everything up
My wife has vetoed replacing the floor with a super insulated one until either the children leave home or the current polished wooden floor needs replacing. The big bugbear is that it cannot be done a room at a time.
Still working towards it - eg,
- currently just about to complete loft top-up to 450+mm (from 250- 300ish) (plus raised storage boarding)
*bigger rads fitted in main room, about to start using these ‘in anger’ for first time, as autumn kicks in, hopefully with another couple of degC knocked off flow temp
*electrician booked in to install dMEV in bathroom (pros n cons heating-wise, but reduces need to open windows, in winter, I hope)
*etc.
Not all the household is convinced about going ASHP next spring…! Let’s see.
PPR have organised a meet-the-installers event here tomorrow evg, so I’ll see what anyone thinks about my various stabs at configurations.
1 Like
I see that you are lowering your carbon footprint already. Every little helps.
When no one can tell whether the heating is on or not but they are warm enough anyway you know that you have really nailed it!
I can’t remember whether you have any rooms that don’t readily get warm enough, if so they need larger radiators. Maybe you could reuse ones taken out from your main room.
Yes will be replacing some other rads eventually, after we’ve been through a winter with the recently-installed new ones in the main room, so’s to get a feel for how best to use them, ie longer-running on-times with lower flow temp, etc.
You definitely need longer run times, particularly early morning. That was something that came out of the Heat Pump Challenge a few years ago.
I took part in the challenge, so as to report results, but I was already running my boiler at less than the suggested temperatures. My heating was coming on 1½ before the morning alarm and as someone was home virtually all day remained on until an hour before bed. In very cold snaps it was on all day and night.
Of course the boiler itself was not on all the time. Even modulating down as far as it could it still cycled a bit.
Yes, no buffer tank, and weather compensation.
Despite floor still not having been insulated, I got through the cold spell in November without needing additional heating, as the HP is keeping the first floor warm (20 degrees +/-ve 0.5) , and I have only been venturing downstairs to cook, and also eat when family have been visiting.
As expected energy use has been a lot more than projected but I had built up a sizeable credit with Octopus over the last couple of years, which I am now drawing down.
1 Like