this post was submitted on 23 Aug 2026
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Central heating systems use recirculating hot water to spread meat from a central heater (which can be a heat pump) to multiple radiators. In theory there's nothing preventing you from connecting other devices to that loop of recirculating hot water to use the heat from your central heating system for those too.
It would however add quite a bit of complexity to the devices and plumbing, which would also make both more expensive.
And it also wouldn't really be worth it. Heat pumps get less efficient when the temperature difference between the hot and cold side gets larger. So while your air conditioning does indeed produce heat, dumping that heat into the outside air at ambient temperature is much more efficient (in terms of watts of heat moved per watt of electricity used) than trying to use it to heat up water to 50° or so to be used as heat source for a dryer. Then there's also the issue of balancing demand and supply of heat. Your dryer could only use excess heat from your air conditioning if both are running at the same time, so the devices need to be synchronised or you'd need heat storage, which adds additional complexity, expense and inefficiencies.
Devices that need heat also do not all need the same temperature. Your radiators, clothes dryer, dishwasher and so on all have different ideal temperatures, and because heating pump efficiency decreases as the temperature difference between the hot and cold sides increases it's more efficient to run it with the lowest temperature delta that's feasible. So it's more efficient to just give each device that needs either heating or cooling its own heat pump (unless you have sets of identical devices which all need the same temperature and that can all be integrated in a single system, such as central heating radiators or floor heating zones). And the complexity involved in distributing heat between unrelated devices in your house makes giving them all their own heat pump likely the cheaper option too.
Systems that circulate ' freon' are fairly common in commercial buildings. They are complex to build and so don't really make sense for houses.
It's possible to heat things like return water or cold water directly and then use heat exchangers.
Temperature differentials also doesn't matter much because temperature doesn't directly behave like voltage, if your hot source is too hot you simply use less hot water (lower flow). You'd likely end up with multiple heat pumps throughout a larger home, but each one can be smaller as they cooperate.
Here in Sweden we already always distribute to homes at 70-100°C and then at 50-55°C internally (again, with heat exchangers to minimize energy loss). And that works just fine. We just don't (yet) have many systems which feed back thermal energy.
You can easily feed back to a central hot water tank, then let the central heater rest as another heatpump returns energy to it.
The different temperatures are not a problem because they're difficult to achieve or anything. Most devices that need heat would have a pretty wide tolerance. The main problem is efficiency, when that heat is provided by a heat pump.
If you have underfloor heating, that can typically work with water temperatures as low as just 30°C. If you have a heat pump that needs to heat up water to 30°C, with outside temperature being at about 0°C (realistic winter temperature here, and it makes the calculation easy), then a good heat pump typically reaches a CoP of 4 (sometimes even slightly more).
If you instead would use an internal heat grid of 65°C (a pretty typical practical maximum of conventional heat pumps, and a pretty typical temperature for a heat pump powered clothes dryer to run at), then that CoP typically drops to only just about 2.
So, if you let your heat pump run at 65°C and use a heat exchanger to run your heating off of it at 30°C, you use nearly twice as much electricity for every watt of heat you add to your house compared to just running the heat pump at 30°C and using the output directly.
Typically the heating in a home is the application that demands the most amount of heat by far. But it's also the application that is usually the most tolerant to low temperatures (especially if you have underfloor heating or forced airflow radiators). So you save a huge amount of electricity by having the circulating water temperature as low as possible, but that also makes that heat not very useful for most other devices (a clothes dryer operating at only 30°C would be highly ineffective).
Heat grids work great if they are supplied by industrial waste heat. But if the heat has to come from a heat pump they're a terrible idea because of how much heat pump efficiency decreases with increasing temperature delta.
https://www.sidite-solar.com/cold-climate-performance-cop-data-air-source-heat-pump-performance-at--25c-real-cop-efficiency-curves-compared-2026-guide-
You assumed 0°C? They solved it at winter temperatures most of Sweden sees.
Any COP above 1 eventually pays off, as long as it does so before the equipment is due for replacement you're good.