Block heater for 3rd Generation Prius: Recommended in bitter cold climates ? Can it be DIY ?

It can be DIY, depending on how good you are at snaking your hand around to where it needs to go (there should be some threads on installation).
Better (in my opinion) in cold weather is blocking the grill(s) to keep the engine from having to run too much to generate heat for the cabin - there are threads describing that too. Pre-slit pipe insulation works really well.

 

1) Is it recommended for cold weather climates (-30 C) ?

We're using ours year 'round, with relatively mild winters on the west coast.

2) Can block heater installation be done by yourself or should a professional/dealership do it ?

The part is about $80~90, and sometimes hard to buy in the States. That's a little perplexing: here in Malibu north no problem, but North Dakota they've never heard of it. Anyway: I would ask a few dealerships about installed price, and if it's $200~250 (in total, with the part), I'd consider getting the professional install. Besides saving you the hassle, there'll also be no finger-pointing, if there's problems with it. I'll try to dig up and attach the install direction though.

3) Does it improve fuel economy significantly in cold weather ?

Any time of the year, with a couple of hours plugged in, it raises the coolant temps about 25C.

4) Any other issues/ concerns you've had with a block heater in a Prius ?

There's been isolated reports of car fires. The main issue I've had is forgetting to unplug. Assume you will and plan ahead. If you're running the wire and plug out through the front/lower grill: zip-tie it VERY securely, at a couple of points inches apart. Ensure the extension cord you plug it into, can pull straight out, and if/when it happens, the block heater cord is not dangling low enough to drag.

 

A screen-grab from the attachment: this picture looks to be taken from below, looking up, and you can see the corner of the exhaust manifold if I'm not mistaken:



I've heard in practice it's no where near this clear, you're mostly going by fee. I do my own oil changes, and I've casually looked to see where it is, never quite spotted it. I think that little indent at 3 o'clock of the yellow circle is where the clip pushes on.

You for sure need to raise the front end, and remove the engine underpanel.

 

This was one of the first tasks I DIY'd on my Prius and it was a pain in my nice person. I've gotten a lot more comfortable working on the car and have since tackled much more complicated tasks, but have told myself I won't replace the block heater if it stops working because it was that fiddly.

 

This is an easy one! I did a few on Mercedes. They screwed in! And the bolt on the block was SUPER tight.
Best to do while the car was cold. But you remove the radiator cap, remove some coolant, squeeze a few hoses and put the cap
back on. This creates a vacuum so when you remove the bolt you don't have a 2 inch stream of coolant shooting on you.
It is best to have the element in your hand as you remove the plug. You'll loose some coolant, but very little.

But with the Prius, no coolant lose! There must be a hold in the block, and you push the element in and it clips in place.
The lube probably makes it easier to install but also helps transfer the heat.
NOT that I need one in Florida, but now I'll have to get the mirror out and see where that is.

 

When you start a Prius, it goes on a mission to get the engine up to normal operating temperature very quickly, so that most of your journey will occur in optimal conditions for MPG. The only way it can get that heat is by burning gas.

Therefore, any heat boost you can give it will prevent gas from being burnt. If your electricity is cheaper than your gas, then consider it a thermal battery and take advantage of cheap grid power.

 

And hey: you've got a "plug-in"...

Recently up the coast, we didn't use the block heater, and I can't honestly say I noticed a difference. All our drives were good distance too. But in town we do a lot of short runs, and the engine sounds happier, often shuts off within 100 yards. And our electricity is only $0.0945 per kw/hr.

Again, I think it can be tough to obtain the block heater in the States? Have to smuggle it in, like bootleg liquor lol.

 

I'm from Winnipeg, Manitoba, Canada and the temperatures here can get to -40 to -50 degrees Celsius in the winter (-40 to -58 degrees Fahrenheit). The block heater definitely helps in that weather. My block heater cord stopped working until I got it replaced and the motor sounded pretty rough starting it in such cold weather.

 

Damming the lower grill with pipe insulation (cheap at any hardware store) works really well. I lived in Montana for two years when I bought my 3rd gen and it helped in a minor but not insignificant way.

Just measure the grill, cut the pipe insulation and slots in it and use zip ties to keep it in place. It won’t rub anywhere causing paint damage and if you’re driving in very cold weather, you’re ICE will stay warmer longer.

 

The block heater is not to heat up the car. It was designed to keep the engine from freezing!
AntiFreeze will freeze, when it gets cold enough.

 

Installation for me wasn’t complicated, just finicky. Big hands are not helpful. There aren’t any tools or hardware. Once you’ve gained access to the receiver hole in the block simply grease the probe (heater) or the hole in the block and slide probe into hole until it clicks. Similar to how a pen cap has a metal clip that grabs onto your shirt pocket. Do not over lubricate otherwise the grease create an airlock preventing the probe from going all the way into the hole and or your hand slips and can’t apply enough pressure to push the probe.

Having lived with -30C winters for 50yrs, my understanding of preheating (block heater or oil pan heater, or as the Russian military does, lighting a fire under the oil pan/engine block) serves several functions;

1) Reduce friction by preventing the oil from becoming too viscous. Oil at -30C takes much longer to get up to all the moving parts at the top of the engine than 10C oil. This prevents wear on startup. This in turn means:
2) reduced friction therefore less load on the starter and battery which has lower output at colder temps.
3) shortened warm-up period so cabin is comfortable sooner and the engine reaches optimal operating temp sooner reducing fuel consumption.

Thermal stress (going from one temperature extreme to another) causes wear. If the temperature spectrum can be reduced, less stress occurs. As the saying goes, one of the worst things you can do to an ICE is start it. That’s why taxis and other commercial vehicles are left idling, especially in cold temps, and last such a long time.
The weather front (grill dam) does nothing to help starting the car. It only helps retain heat being generated once the vehicle is in motion.

I use a block heater and the pipe insulation weather front.

 

Did you work from above or below? I disconnected and pried/tied/pushed all the conduits and bracket in the way as much out of the way as possible, and trial-installed heater element into the hole (just to make sure it was physically possible), then backed it nearly out, applied the grease a fingertip dab at a time. The actual install from below, with the conduit cajoling mostly from above. Can't recall if I removed the wipers and cowl. Think I didn't, and that might have made from above a lot easier. Not sure.