Thermodynamic energy

I am doing a refurbishment project, and like the idea of thermodynamic heating and hot water, but I can’t find balanced info…the suppliers make unsubstantiated claims, along the lines of" all the hot water you could want for £120 pa to run the compressor" to “emperors new cloths avoid like the plague” possible written by solar thermal competitors. Does anyone have either personal anecdotal evidence or preferably unbiased verifiable data ?