I have district heating from a combined heat and power plant, which should be 80+% efficient. A solar air to water heat pump could be more efficient at 29% * usually 200% but sometimes 400% (For reference, traditional gas boilers only go up to 94%.) = 58% to 116%, the latter might require ground instead of air. CO2 is a relatively safe refrigerant.
According to ChatGPT: The efficiency of a typical modern steam turbine in a power plant is around 30-40%. Fuel cells can achieve efficiencies in the range of 40% to 60% or even higher for solid oxide fuel cells (SOFCs). Those and molten carbonate fuel cells (MCFCs) are used in combined hea