Which of these heat pumps is best for old houses with radiators?

Vaillant aroTHERM plus is often a strong option for modernised old houses, because the R290 refrigerant allows higher flow temperatures than many standard systems. However, each case requires a heat load calculation and careful design.

When does NIBE SMO S40 make the most sense?

NIBE SMO S40 is attractive when you need a flexible controller for several heating circuits, buffer tanks or hybrid systems. It is well suited to complex hydraulic layouts.

Vaillant aroTHERM plus vs NIBE SMO S40 vs Vitocal 222

Quick summary

Vaillant aroTHERM plus: R290, high flow temperatures, strong hot water performance
NIBE SMO S40: flexible controller for complex systems with several heating circuits
Vitocal 222: compact indoor unit with integrated hot water storage
Best suited for: premium new builds and modernised homes looking for future-proof systems

Overview of the three systems

All three systems are designed for residential use, but their positioning is slightly different. Vaillant aroTHERM plus focuses on R290 and higher flow temperatures, NIBE SMO S40 is a controller concept for more complex systems, and Vitocal 222 is an integrated indoor unit that keeps the installation footprint small.

For many homeowners the key questions are: Which system can handle my existing radiators? How quiet is the outdoor unit? And how well does the heat pump integrate with photovoltaics?

Key technical comparison

Aspect	Vaillant aroTHERM plus	NIBE SMO S40 (with outdoor unit)	Vitocal 222
Refrigerant	R290 (propan)	Typically R32 / R410A depending on outdoor unit	R32 series depending on model
Typical flow temperatures	High, suitable for many radiator systems	Medium to high, depending on outdoor unit	Primarily for low-temperature systems
Indoor footprint	Separate hydraulic unit and hot water tank	Controller and hydraulics, external storage	Compact indoor unit with integrated storage
Best suited for	Premium new builds and modernised old houses	Complex installations with several heating circuits	Standard new builds with underfloor heating

Noise and placement

All outdoor units must be positioned carefully to avoid noise issues in dense neighbourhoods. Vaillant and the typical NIBE outdoor units offer low sound levels in partial load. Vitocal 222 depends strongly on the chosen outdoor unit. In all cases check local noise regulations and consider the distance to bedrooms and neighbours.

Act now while incentives are still attractive

Government incentives, tax credits and rebates can significantly reduce the up-front investment and shorten the payback period of a heat pump.

Many programmes in the US, UK and EU are time-limited or adjusted every year.
Some schemes have fixed yearly budgets that can run out during the year.
Homeowners who act early often secure higher grants and better conditions.

Installing a heat pump while incentives are generous can therefore noticeably improve the overall economics.

Conclusion

Vaillant aroTHERM plus is a strong choice if you want a future-proof R290 system with high flow temperatures and excellent hot water performance.
NIBE SMO S40 works well in complex buildings with several heating circuits, buffer tanks and possibly additional heat sources.
Vitocal 222 is ideal for compact installations in typical new builds with underfloor heating and limited indoor space.

For homeowners primarily interested in price versus performance you may also want to read the heat pump price-performance comparison.

More heat pump comparisons

Next comparison:
Panasonic Aquarea vs Daikin Altherma vs Mitsubishi Ecodan