hybrid MPG vs outside temp
 

I would like to see notes such as temperature when recording information on hybrids. When temperature dropped into the 3-40 deg F. range, I saw my mpg drop 6-7 mpg.

You will notice decreased mpgs in colder, especially subfreezing temps. The engine has to run longer to warm up and keep the emissions equipment warm. When the engine is off at stop lights, etc, or when driving on battery for a prolonged period, everything will cool down and the engine may have to run to warm up again. Thus, you are forced into burning more gas when it is cold. Additionally, cold batteries don't work as well as warm batteries. There are other reasons for lower mpgs when it is cold, also.

What supplies cabin heat in a hybrid? In conventional cars the heat comes from waste engine heat. If the engine isn't running does the heat come from the batteries? Or does the heating system cause the engine to run more to supply cabin heat? Either way cabin heat ultimately comes from the fuel tank.

Some hybrids/electric cars have solar pannels, such as the Nissan Leaf, but not sure what for, probably running some of the low volt electronics and/or topping up the batteries. French cars seem to be leading the way with fully electric vehicles, they have at least 3 or 4 electric cars available and a whole range of vans too, but I think the limited range means hybrids will always be more popular.

I try to add notes about prevailing temperatures when adding a fill-up. RebelHybrid explained the main reasons very well for those cold weather drops is MPG. My Camry Hybrid drops about 5 MPG in winter, as did two previous Prius models. Some drop in MPG also happens in summer with the extra A/C. I love those Spring and Fall days with super mileage.

My Prius has dropped below 30 mpg the last two fuel-ups thanks to the sub-zero temps we've endured this winter. The seasonal variation in my gas mileage is huge; in the summer I was getting 46 mpg. It would be great to have a spot in Fuelly to record average temperatures or ranges so that I can compare my results with others operating under similar conditions.

Yeah, the cold can really hit hybrids hard. My FEH struggles in the winter to keep the mileage up.

hybrid mpg vs outside temp
 

I also put notes about temperatures and indicated car data after each fill up. I also fitted a grill block on the lower radiator. My CT200h is getting a reasonable 4.8L/100km - 59mpg/UK - 49.13mpg/US.

Michael.