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The answer is simple: just don't turn the heat pump off. Problem solved.

Now, the misconception is that people are thinking in terms of "if it's on, it costs a lot of energy, if you turn it off, you save that enegry". But for heatpumps, that's not true. Running them 2 hours with 50% eletrical power costs less energy than running them 1 hour with 100% eletrical power.

The efficiency of heatpumps is non-linear, whereas it is linear for radiators which is unfamiliar to people.

That's very interesting! And of course, it'd be very unintuitive for most people. Maybe more education is needed to help people understand how to optimize their energy bill with heat pumps.

Yeah, there definitely needs to be more explanations and guidance in using them.

There's at least three types of heat pumps:

- air-air heat pumps which function like "inverted" AC, which is what you were thinking of - another quirk being that in some models the air vents have optional electric heating which provides more instant more intense heat at the cost of massive energy use

- air-water heat pumps which use air to heat up water similarly to a conventional boiler - a noteworthy difference is that they usually target 40°C instead of 60°C but like other heat pumps they're very energy efficient and are typically used with floor heating

- brine-water heat pumps which use brine running through underground pipes to heat up water similar to air-water heat pumps - these are arguably more efficient but more expensive to install due to the excavation necessary to lay the heat exchange pipes

The latter can further be categorized based on the layout of the underground pipes (YMMV on the exact nomenclature as English is not my native language):

- area collectors use a horizontal grid requiring a large area of land and limiting its use for things like trees or swimming pools (or anything that needs to go deeper)

- trench collectors use a vertical grid, essentially turning the area collector on its side - these of course require much deeper excavation but have a much narrower footprint but depending on where you live you may need to get additional permits

- basket collectors use a three-dimensional grid, usually split across a number of "cages" or "baskets" combining the footprint advantage of a trench collector with the depth advantage of an area collector

In Germany air-air heat pumps are the default with many prefab construction companies due to the ease of installation. When we built our house with a conventional construction company we went with a water-air heat pump because that's what the plumbing company was most experienced with. A brine-water heat pump would have been a good option due to the soil consistency and ground water level but sadly national regulations enforced a minimum depth much lower than what would have been otherwise possible and this made the option cost prohibitive for us.

The main advantage of air-air heat pumps is that they can be better used for cooling (because at the end of the day it's literally just AC) whereas other heat pumps are usually capped by the dew point to avoid condensation.

That was an insightful comment and immensely helpful! Thank you

I don’t think that’s true for modern isolated (passive) houses built in EU standard. And heat pumps don’t need to be air based, a lot of them transfer heat with water radiators inside the floor.

I didn't know that! So I was thinking on the typical air conditioner that on winter can be switched to output warm air instead of cold.

Around here those are the only ones not subsidised because they are less efficient and usually only a single room solution.

If you have a heat pump driven water boiler for your hot water supply you even get the bonus of allowing it to cool the room in the summer (if properly installed with a switchable duct for winter usage).

100% agree. I find the "passive" heating options like radiators or floor heating much more comfortable than being blasted by hot air from above.

You can have floor heating with heat pumps, too. Just heat up the water to a lower temperature (~40C) for longer. It's still way more efficient than burning gas.

I actually thought floor heating was standard for heat pumps (maybe it's a european thing tho)

Not every house can have floor heating without prohibitively high costs.

It doesn't make sense, though. You need the same amount of energy to heat up a room, regardless of how you produce the aforementioned heat. If the energy immediately dissipates, it means the building has very poor insulation.

In order to heat up a radiator you need very hot water (>60C), that takes a while to heat up and then sits in the radiator slowly cooling off. Simply keep the air pump on for longer at 20C and you'll get the same temperature for _way_ less energy consumption. With a radiator you simply consume more energy upfront, you don't save money (on the contrary, you spend way more if the electricity doesn't come from fossil fuels because burning things is not efficient by any metric).

This doesn't make any sense at all. Standard heat pump installations include a buffer tank (usually at least a couple 100 liters but possibly much more depending on the details of the installation). The heat pump does not heat the house directly, but the buffer tank. The buffer tank in turn sends warm water to the radiators and warm water faucets, etc.

This is the same principle as in traditional gas and oil boilers. The only difference is that in newer, well insulated buildings, radiators need much lower temperatures so they may feel colder to the touch (i.e. you don't burn yourself on a radiator anymore).

But modern heat pumps also can provide relatively high temperatures in case of installation in older buildings with legacy radiators (70°C are not really an issue anymore).

"So heat pumps exist but just as a "not very good" alternative, relegated for things like small secondary homes at the beach (where it doesn't get too cold anyway)."

In Germany, famously not a very warm country, heat pumps are used in well over 50% of all building projects requiring a permit (this includes renovations). Heat pumps are the definite standard, not an "alternative".

Talking about air conditioner-style heat pumps here,

> as soon as you turn it off

You're not supposed to turn it off - then the room will get cold again. Spending the energy to heat up the whole house and radiator mass is very energy-inefficient. Just leaving the air heat pump on the whole time, letting the thermostat regulate and just heating the air inside the home is more efficient, even though it's "running for longer".

That sounds like really bad insulation. Energy, in form of a hot or cold air shouldn't simply disappear from a properly insulated dwelling

Why is this a contradiction. Modern heat pumps at least in Germany are using the normal water based radiators. It is true that they are more efficient if used with floor or wall integrated radiators. But they are already more efficient looking at the current energy mix (and the current load) here by just exchanging your gas or oil based central heating with a heat pump.

I've never heard that hearing. I've been living in multiple houses heated primarily with a heat pump in the winter during average temperature of minus 10 Celsius, ranging from 0 to -30.

My current garage has radiators installed but I've never used them as the heat pump is just fine.

I guess they must build the houses or heat pumps differently where you live!

I have a heat pump, it heats the water in my radiators. That's the typical installation here in the UK.

It shouldn't work like that. The heat doesn't "know" if it came from a radiator or a heat pump. That should not matter for how fast the same heat dissipates.

It does, to a degree.

With air-air heat pumps you get warm air and the air has to warm up the walls, furniture, ground and so on. Warmer air rises so in order to warm up the ground (or your feet) it has to displace/heat all of the cold air first. If you vent before the room itself has been warmed up, you have to start over.

Floor heating on the other hand heats up the floor and anything standing on it first. The heat still rises but by the time the hot air has displaced/heated all of the cold air, everything else will already be warmed up and give off heat if the air is vented.

Of course the correct answer is that heat pumps don't need to be turned off because it's actually more energy efficient to run them at lower settings for longer. And with proper insulation heat loss from air currents is less of a problem so this is more of a consideration for heating up a room from scratch (e.g. after turning down the heat pump during a vacation).

The radiators act as a heat reservoir that lasts for a while. If your heat pump blows air ac style it can never stop.

Ofc you can hook the pump to a water circuit with traditional radiators…