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The average price for electricity in the Netherlands is around 50cents /kWh Some electricity providers have off peak rates that are between 10-40cent/kWh That could also be an interesting solution to use an immersion heater and buffer tank (like a battery) and charge it with low tarrif electricity and solar energy. This would have a simiar operating cost as a split heat pump and much less upfront investment cost. Very interesting idea, thank you! I will investigate!

Yes that is what I thought too. So I had another company also do the heat loss calculation and they came to a very similar result. There is a very specific methodology in the Netherland that all professionals follow to make an official heat loss calculation report. I asked about this and he said they need to assume all the worst case scenario of a very cold winter with extended temperatures of -10 degrees which almost never happens, but theoretically could happen. The professional I hired did the calculation for the ventilation heat pump which he said uses more energy because it has to continuously heat up large volumes of outdoor air so he added +16W/m2 for ventilation loss. The true heat loss is about 28W/m2 (in extreme conditions) the Absorption loss is a safety factor they also use here. But it is comforting to hear that your home is over double the size and uses less energy than we have modelled. If we used a split heat pump with balanced ventilation (with a heat exchanger) we can cut the ventilation loss out and if we take the safety factor out then the actual energy consumption will be more in the range of 2600kW/yr for space heating in an extreme winter and probably in a normal year the space heating demand will be more like your house using about 18-20W/m2

Okay good to know! Thanks. In my case we have a really low DHW demand so I guess the Vailliant Arotherm like my advisor suggested would make the most sense.

Yes the Ecodan can also run in reverse and cool water to a temperature of 5°c But if you have floor heating with hardwood floors there are issues with condensation (mold) so is most safe if you have a concrete floor. The cooling function does not work that great with radiators but helps a bit. The mini-split is better at cooling and also dehumidifying, and can also heat in the winter so if cooling is important then a mini split might be a better option.

Thanks @Beelbeebub for you elaboration of the difference between the technology of the Ecodan and the Arotherm. Yes indeed the Ecodan is more exotic and operates at about 20degrees higher so would be ideal for a traditinal high temperature radiator retrofit or if you want a smaller indoor unit and more DHW: Ecodan 200L 1600x595x680mm Arotherm 190L 1880x599x693mm I was more trying to get a grasp on categorizing the different types of heatpumps (air-air, air-water, and water-water) categories and costs. To me I see the Ecodan and the Arotherm split heat pumps in the same family (air-water) with a specialization in high or low temperature heating output. Both are very efficient and get good reviews and depending on the heating system and installer preference could be a wise choice.

Thanks for the info @markocosic. Yes indeed it is not very obvious which one to choose, which is why I wanted to post some of my findings about the ventilation heat pump to help inform others what I found. To respond to your comment above: each house has a unique set of parameters that needs careful consideration. 1) Small, Medium or large house 2) DHW demand High or Low 3) Climate cold, mild or hot 4) Existing build or new build 5) Well insulated or not 6) existing radiators (high temp) or floor heating (low temp) or ducted system (air) 7) Local installers preference, parts, maintencane & service (the more common the cheaper it will be to maintain) 8) Budget and operating cost targets. 9) Ground source option, Split outdoor units possible, or no outdoor unit possible. 10) Personal comfort: floor heating, airconditioning, radiators, In my case we are building a new, small, highly insulated house in a mild climate with a low DHW demand, good Vaillant and Mitsubishi service and have an option to have an outdoor unit. So that narrows it down to basically three options: Air to Air (no outdoor unit) Air to Air (outdoor unit) Air to water (Split) Here is a general estimate of the cost and comfort of the three options: 1) Air to Air ventilation (Genvex Combi 185 or similar) €8000 + installation €2000 is also the balanced ventialtion system. Operating costs €1700/yr comfort 5/10 Cost after 10 years = €27000 2) Air to Air split (Mitsubishi multisplit) €2500 + installation €2000 + balanced ventilation €1500 + Water heater €1000+ Operating cost €900/yr comfort 7/10 Cost after 10 years = €16000 3) Air to Water split (Ecodan or Arotherm) €8000 + installation €2000 + floor heating €4000 + balanced ventilation €1500 + Operating cost €600/yr comfort 9/10 Cost after 10 years = €21500 So conclustion: If you are on a budget and value having airco more than floor heating go for option 2. If you want more winter comfort, DHW and quiet, with less summer cooling comfort go for option 3.

Hi thanks for the link @Beelbeebub, It looks like a good system. As mentioned above my advisor specified the Vaillant Arotherm plus which is very simialr to the Mitsubishi Ecodan you referenced. Both are good options and both cost roughly the same price and are similar in performance and noise levels. https://www.vaillant.co.uk/homeowners/products/the-arotherm-plus-air-to-water-heat-pump-71360.html I was also trying to compare & consider the investment and operating cost of each system to make the comparison more clear to someone new to this topic. 1x Cost = Air to air split heat pump + Electric water heating cylinder + Solar panels would have a slightly higher operating for normal hot water usage down side is it has indoor & outdoor units. 2x Cost = Air to water split heat pump + floor heating is more comfortable and only a slightly lower operating cost for noramal hot water usage the down side is it has an outdoor unit 2x Cost = Air to Air ventilation heat pump + floor heating the operating cost would be about 2.5 times the cost of a similar air to water split system but has the benefit of no outdoor unit. 3x Cost = Water to water ground source + floor heating would be the ultimate solution as it is completely silent, has the lowest operating cost and the benefit of no outdoor unit. What surprised me was the much higher operating cost of the ventilation heat pump due to the lower COP efficiency. I would say the air to water split heat pump like the one you mentioned (or the Arotherm) is probably the best value / comfort for money. The air to air could also be a very practial solution if you are on a tight budget.

Regarding the discusion around ventilation heat pumps specifically the Genvex Combi 185. I was initially quite enthousiastic about the compact simple solution of a ventilation heat pump. After modelling the energy consumption it seems to be less efficient than I originally hoped (see attached summary) The house I am building is an apartment for two people with a floor area of 70m2 in the Netherlands (similar climate to England) Insulation is relatively high: Floors: Rc 4,8 m2K/W Walls: Rc 6,1 m2K/W Roof: Rc 8,2 m2K/W Windows: U-value <1.0 [W/m2K] After a heat loss calculation was made by a professional it was determined the annual heat consumption would be approximately 5280kWh/year Heat transmission loss: 28W/m2 Ventilation loss: 16W/m2 Absorption loss: 14W/m2 Essentially the conclusion was the ventilation heat pump would rely on the back up immersion heater which has a COP of 1 far too much in the cold months to heat the air and hotwater cylinder. This basically translates into an operational cost of about 2-3 times higher than a split air to air or air to water heat pump. If your electricity cost is reletively low then this is less of an issue, if it is high such as where I live (around 50 cents/kWh) then the operational cost is an important factor to consider. Attached is the annalysis that I made of the Genvex Combi 185 that perhaps someone considering a ventialtion heat pump might find useful. Similar values would also apply to the Nibe F470 or Nilan Compact S as they all similar in performance and function. Installation conclusion based on total investment and operating cost (assuming you have space for a split outdoor unit) : Economical option: heating and cooling with a 5kWh mini split (Mitsubishi) and using a 120L electric water boiler for domestic hot water combined with a shower drain heat exchanger powered with 4 x 400wp solar panels. Comfortable option: (about twice the cost) was to use a Air to water split heat pump and integrated 190L water boiler (such as the Vaillant aroTHERM + unitower heat pump) combined with low temperature floor heating, shower drain heat exchanger and 4 x 400wp solar panels.