Riga, Latvia


Demo responsible: Riga Technical University 

Type of building: Small residential, consisting in two single-family-houses (2012/2013) in Imanta and Sunisi.




Heated space

235 m2

96 m2

Electricity consumption

~4.4 MWh/year

~7.2 MWh/year

Gas consumption

~39.6 MWh/year

168.5 kWh/m2

~21 MWh/year

218.8 kWh/m2


Individual gas boiler for DHW and space heating through radiators (Imanta, Sunisi) and under-floor heating (only Sunisi)

Demonstration action:

  • TP2 consists of mixed solar-assisted integration of gas-driven thermal compression heat pump with boiler (Boostheat) for space heating and Domestic Hot Water (DHW)
  • Hybrid solar PV-T panels (DualSun) to assist BH evaporator and for preheating and for the electricity production for building appliances coupled with glycol storage and stratified thermal storage tank (Ratiotherm)
  • Smart Energy electrical heater for residual PV-T electricity

Technical and social risks & difficulties:

The initial assessment is that there is very limited risk in coupling both innovations (i.e. HP boiler and solar hybrid PV-T). However, several challenges were observed during the deployment phase:

  • The technologies are unknown to the Latvian market and the installers have limited experience
  • Successful integration of controls requires active involvement of all technology providers
  • Unfamiliarity and precaution of potential end-users to decide to swap their existing ”old, reliable” gas boiler with a completely new technology package consisting of several components
  • The new technology package needs much more space compared to the old gas boiler, so the existing boiler rooms were not suited for that and other premises were used
  • The procedure for approval of solar panels was significantly relaxed in Latvia during our deployment phase (now approval of municipality is generally not required)
  • Approval of new gas piping installation time-consuming, long waiting lines of the gas DSO as a result of Covid-related restrictions and a lot of construction work ongoing

Replicability potential:

  • Small residential (single houses 30% in Latvia) with natural gas connection (48% of dwellings in Latvia)
  • New and renovated buildings
  • All climates


  • 37% of primary energy and cost savings
  • 43% of self-consumption ratio from PV

Lessons learnt:

• PVT panels with polypropylene caused a variation of pressure in the commissioning that affected the installation

• Gas-driven CO2 heat pump could not run with pressure variations. For several reasons, it had a lot of leaks and stopped running

• Nevertheless, in Sunisi 1733.2 kWh of gas were saved in the period of February to August. It did not lead to cost savings due to the increasing cost of gas. Anyway, comfort is always met

• CO2 heat pump will be replaced with a hybrid concept (compression heat pump + gas boiler for peaks) which will allow self-consume of the PV production for the electric heat pump

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