Engine Block Heater = Quicker Cabin Heat?

When the engine is warm, the heat will start to flow into the cabin quite quickly.

A few minutes will pass and it will be comfortable.

For example, the engine warm-up schedule from -22°F (-30°C) to 158°F (70°C).

Temperature2 by MAX2 posted Feb 21, 2025 at 11:33 AM

After the engine warms up, the heater is turned on and warm air begins to flow into the cabin. Otherwise, you drive cold air with the fan.

 

Well that's a pretty simple thing it seems like if you have the coolant in the system pre-warmed up to let's just say 88° then you can have 88° air coming out the vents upon the starting of the car but for the ice engine to come on you're going to have to have the heat on the fan on in other words a call for heat like a thermostat in your house so I tend to not use the numbers I use high and or low for air conditioning so if you were starting out with 88° water temperature whether you drove yesterday and there's something in the coolant heat storage tank would be irrelevant You're block heater or your inline radiator hose heater is heating the fluid all night whatever until it gets to its set point that's built into the block heaters system then it shuts off and then when things cool again to the preset that's built into the heater it comes back on again kind of like a heat tape on your water pipe in house . And here in the southeast it's been getting quite cold the last few winners like I've gotten down into the single digits here and when I go out in the morning and get in the Prius even when it's in near single digits now I have heat starting to come out the vents and 2.5 mi now granted it's not warmed up completely and it's not you know crazy heat which I'm really not looking for I'm dressed for the weather so I'm not looking to be baked by the car another mile with the heat blowing on medium and I'll be turning the fan down to low and then another two or three minutes the fan will probably be off and just the normal flow through across the core is ample The sun is coming up and all that but these kids you know they want to ride to work in 13° weather with the open toe Birkenstocks on and shorts

 

I've never tried one in a Prius but it made a dramatic difference in every other car I've equipped with one.

You can get the cabin warm faster-still with a mains-fed 120 cabin heater or a gasoline-fired cabin heater, but those are both difficult to install in a compact car like the Prius.

The block heater is a very good bang for the buck.

 

We’ve been using the block heater (with 2010, 3rd gen), for cold starts, year ‘round. This is since purchase, late in 2010.

in the early years I monitored engine coolant temp: with 2 hours BH use, immediately after start-up I’d see +20C above ambient, and that would become +30C within a few seconds, presumably as the coolant homogenized.

That 2 hour usage typically plateaus the temp, on our west coast, lower mainland climate, but for bitter cold conditions 3 hours would likely do better.

Any time of year it shortens time till you get cabin heat, as well as engine shut-off. Not miraculously, but noticeably.

There have been fires with these, worth noting. Our first one was dealership installed, and shorted out after about 10 years, right where the wire went into the heater element, one pop and puff of smoke.

When i replaced it I saw no evidence of heat transfer grease, not even residue, looked pristine clean. That might have been missed by the dealership “pros”, and a factor in its demise.

I DIY’d the replacement, and it was a pain, mainly due to everything in the way. If you go that route I can share tips.

I’d recommend to have your extension cord plugging into a box with its own breaker, that cuts the power near-instantly. Consider a timer too, for early morning starts. A good idea to have smoke detector and handy fire extinguisher too.

I ran the BH cord-and-plug out through the lower grill, securely zip-tied, with just enough dangle to be convenient, not enough to drag if you forget. Also the extension cord connects straight-in, looped around a strong point, so a little tension and the two will separate. For when you “forget”, which will happen. Also I make it a habit to always walk around the front of the car before getting in.