Block heater in the summer time
 

Where I'm from the summer mornings are pretty cool. Typically when I go to work I'd expect maybe 10C (50F) in the morning. I've noted that the small 1.3l engine of Honda Jazz takes about 1,5km (1 mile) to reach the level of "not-so-terrible" efficiency. During that distance it consumes twice the gas it usually does. I lose about 5l/100km worth of efficiency for that distance when the engine is cold.

So that got me thinking how to reduce that distance - to zero even? And now I have! This morning I plugged in the 550W block heater and had it on for about 2 hours. When I got in the car the engine coolant was already at toasty ~50C, instantly giving me good mileage.

Doing the math:
Electricity: 550W * 2h = 1,1kWh = 0,11 euros
Gasoline: 5l/100km * 1,5 km = 0,075l = 0,11 euros (1,5€/liter)

So in my case 2 hours is the break-even point. At 2 hours it doesn't really make a difference if I use electricity or gas to warm up the engine. More tests will follow to see if I can find an optimal time for pre-heating. There might be a sweet spot somewhere around 60-90 minutes? I'm also interested to see the impact at the fuel pump.

Same "efficiency" works here in Arizona...use heater in A.M. to ensure immediate warm-up and highest vehicle MPG...right from the start.

As you mention, the only question is "how long" warm-up is needed and is it cheaper than the gasoline savings.

Yep, block heaters even in the summer can produce great results, especially for those with short trips.

I use my block heater all year!

I use the EBH on my subaru quite often in the summer as well.

I use my block heater when I have opportunity. Warmup time on the Insight's 1.0 is pretty short because it has a water jacket over the header, but the math still works out in favor of using it.

Does anyone know if there's any point in using a block heater with a daily driven Prius, due to its hot water reservoir?

Yes, it still helps a fair amount. The Prius has a pretty horrific cold start penalty. You can't EOC and other things unless its warmed up.

Another one to point out is a heater pad on the oil pan. I did this recently and noticed even further improvements in MPG on my short drives, as well as better idle.

I plug my car in every night and have a timer setup to warm up my car for about an hour or so before I leave. Anything more than this doesn't give much benefit in heat. (though, I should do another graphing session on these temps for VS ambient temp, that would be interesting...)

I had an oil pan heater on my previous car. I connected it to an X10 circuit so whenever I got up in the morning, the first thing I would do was to push the button turning on the heater. By the time I got out to the car it had had about enough of a warmup. This is another thing I need to get done for my current car.

I've been collecting data via the OBD2 port for the past month now, and here are some interesting results. I'll let you make the conclusions.

I filtered out all trips shorter than 5 kilometers.

http://i.imgur.com/SttfbOd.png