Homemade garage floor car heater ?

IMHO, the block heater makes more sense from an energy conservation perspective. Unless you have a naturally occurring source of heat (i.e. a hot spring that you can pipe into your garage), heating the block directly is far more energy efficient than heating the air around the car. Further, the block heater will result in a higher initial temperature.

Your best bet is to have the EBH on a 2 hour timer. Some timers have battery backup. When you install the Enginer kit, you can route your EBH cord through the firewall, under the door sills (with a short extension cord), and plug into a battery backup timer that is also connected to AC power cord for the charger. After you arrive home and plug in, the Enginer kit will take about six hours to charge, then a few hours later the EBH will turn on and your car will be soon be ready for the next commute. Or have two plugs in your bumper to run the Enginer charger and EBH separately, with the timer plugged into the wall. Having a timer is very important, as temperature convergence is around two hours; beyong that, most EBH heat is radiated away rather than being captured (thanks to Bob Wilson for his EBH analysis a few years ago).

Parking in a garage with a little heat (i.e. 50F/10C) will help your traction and Enginer batteries as well.

 

Be very careful with heaters in the garage. Use electronic thermostat ones only. You can get spilled gasoline in a garage. Gasoline vapour is heavier than air. It pools on the floor. If you get a spark on or near the floor you will have an explosion. That's why most garage heaters are mounted on the ceiling.

BTW, the block heater has no thermostat. It's a 400W device as I recall. It's been three years since I measured it. Put your timer up off the floor, at least 1 metre..

 

This is where my Prius goes when it is cold out.

http://mbu.com/house/garage/

 

I have a Reznor direct vent natural gas heater in my attached garage. It is CSA certified for both residential and commercial installation

There are many advantages to heating the entire garage: entire car including transmission fluid and wheel bearings are kept above freezing (Kind of helpful at -40), no ice or snow in wheel wells or under vehicle, less chance of ice up

Some may wonder if a vehicle kept in a heated garage will rust faster. With a natural gas heater the answer is no, it keeps the interior bone dry. But its important to have a floor drain in the garage. Once could also rig up a HRV to exhaust the interior air and replace with bone dry outside air

My neighbours who park outside their power bill to leave a vehicle plugged in exceeds the approx $40 a month it costs to run my gas heater. Their vehicles also rust faster, as the vehicle experiences condensation constantly

 

Would some sort of heated water loop work? I know you are in Canada, but would a solar water heater be feasible? They are relatively inexpensive to build and I have seen them used to heat entire floors in the winter.

 

They use glycol in the loop to prevent freeze-up. The further north you go, the less solar power there is available. Right now in Edmonton the sun is not very high above the horizon. It also rises at 8:30 and sets at 16:15 or so. Not much time to heat the system! Then there is the problem of trying to keep the heat in the collector -in- the system. It's typically -10C ambient right now, and dropping day by day.

However, it's not a lost cause. My garage is insulated but not heated. Well, it's geo-thermally heated (from the floor sitting on the ground). Right now it's close to freezing in the garage. At worst (end of January beginning of February) it gets to -10C in the garage and -20 to -30 outside.

Pearl likes it in the garage!

 

Radient infloor heat does work, but still isn't widely used up here. The Reznor heater I use can be seen tucked up in the corner of the garage, the upper left of this photo



The fan circulates the air around, and keeps the garage bone dry in winter. In January it adds around $40 to my gas bill

Another option, which a co-worker has and swears by, is a radiant heater. This one is made by Schwank

Schwank Infrared Heaters: Radiant Gas-fired Commercial & Residential Infra-red Heaters

No matter what system, it's very important to have a frost/thermal break for the garage slab. Frost line here can reach down 5 ft. So that means the edge must have foam board insulation on both sides, down to the footings

There should also be a thermal break for the slab itself, such as these products from Beaver Plastics

Beaver Plastics insulworks hydronic heating insulation

Beaver Plastics Dynavoid

Beaver Plastics Dynaflex Void Form

Othewise the heat will literally be sucked out of the slab into the soil underneath