I’ve had a similar Rinnai direct vent heater similar to the newer model for over 3 years. It replaced an older Italian made direct vent heater that was poorly designed. The Rinnai has a digital thermostat and uses a piezo lighter. It comes on reliably and there’s no pilot light at all. It direct vents to the outside through a very small pipe and is very easy to install. This heater heats my office in Connecticut from October to April reliably and efficiently.
It has a low setting that keeps the temperature above 5OF and then you can set the thermostat from 60 to your preference. When it’s 0°F outside my office is comfortable and my total heating costs for the season are around $300.
They have versions for propane and natural gas. If you have a small space that needs to be heated reliably you should consider one of these heaters. They also have larger models but I’ve never tried them. I had considered putting in a heat pump/air conditioner (Mr.Slim). It would be interesting to see which would be more efficient/costly to run.