Prius Prime Advanced, car lower battery mileage suddenly?

I seem to remember others on this forum have measured differently: AC settings always result in higher power drain than the seat heaters.

 

isn't heat pump electric as well?

 

For total amount of heat output the A/C should be less than electric direct heat. If one could be happy with just a warm fanny as opposed to being comfortable I suppose. Then again the benefit of keeping the cabin warm on A/C heat pump should allow the battery to output more as well since the batteries are in the cabin with you. I suppose it is all in perspective and reasoning. The length of drive should play a big role in which one chooses too.

 

Generally the electric production of heat is at or near 100% efficient, no matter the means.

 

Dept of Energy says:
“If electricity is the only choice, heat pumps are preferable in most climates, as they easily cut electricity use by 50% when compared with electric resistance heating.”

So the electrical heat is 100% given off to the user, but using a heat pump you get 150%. That’s because the electricity is converted to heat energy in the form of work. This work is also giving off heat energy in the form of removing it from the outside and pumping it into the cabin. If you research cost of direct electric heat vs heat pump efficiency you’ll see it works in most places. The process is less efficient as the temperature outside the vehicle drops to be extreme cold. Heat pumps are not normally used in New England, but Toyota has also built in a gas injection system to assist.

 

If the department of energy is telling you that your 5 watts of electrical power is going to generate 7 watts of heat, then the department of energy is plain wrong.

It violates the first law of thermodynamics

 

Actually they are correct. I know it seems counter intuitive but the entire southeastern United States would have been duped into buying heat pumps to heat their homes if it weren’t true. The laws of thermodynamics actually prove the fact. The amount of heat gained from compression is 100%. Just to pass this heat into the cabin would be 100%. The refrigerant is then converted to a gas by being boiled by the cold outside air removing heat from outside (counterintuitive). This heat removed from outside is passed back into the cabin after the heat of compression is added to it, thus increasing the total energy moved. You don’t get 150% out of the electricity used, but the use of the initial energy gives an offset of more than 100%. 50% of the heat is pulled from outside and added to the cabin. So 100% electricity from compression is added to the cabin plus 50% heat from outside is passed into the cabin as well.

 

My apologies , you are correct.

It is an open system, not a closed one,

So 5 watts from electricity, plus 2 watts from outside system gives 7 watts.

jp

 

Hence using the heat pump is more efficient than the electric heat in the seat. But all this goes out the window if for two reasons. A short trip it’s probably not worth heating the whole cabin when you only need a small boost under the tush. The other reason would be if it is extremely cold this process is less than 150%. That’s why y’all up there in New England don’t use heat pumps. You’d need an extremely large A/C unit to heat your home, and the glubment subsidizes the cost of heating oil.
Don’t get me wrong I’m not against subsidies, the original constitution was built around subsidizing, but they only work if they are dynamic and well thought out. The benefits should always be for the good of all not for a select few.

 

We use furnaces to heat our homes up here.

 

I’m only familiar with my parents home in NH which used heating oil in the furnace.

 

we use heating oil in our boiler.

 

Previous home used oil, man that was old fashion

 

yup, wish we had gas, solar, anything but.

 

I've seen several installations of "geothermal" heat pumps in the Boston area. This kind of "geothermal" is not the same as tapping a volcano or a geyser. More accurately it's called "Ground Source Heat Pump" and it works by circulating coolant into wells driven several hundred feet into the ground. Because the ground stays warmer in winter and cooler in summer than the outside ambient air temperature, the heat pump is able to extract latent heat in the winter and deposit heat (air conditioning) in the summer.

The landmark Trinity Church in Boston, built in 1877, is now heated and cooled using this technology. You can read about it here.



Because the initial cost of this technology is high, it is being used mostly for institutional buildings (government, schools & colleges, large hospitals, etc.) where the cost can be amortized by an owner who expects to be operating the building decades into the future. The high front-end cost of installing such systems is offset by greatly reduced annual operating and energy costs.

For more information about this technology, see the Massachusetts Department of Energy web page here.

 

My sister in-law installs them in some Maryland homes. She is a builder. Most of the costs are attributed to finding either a large well and tapping it at far ends or laying pipe. The well method usually ends up cheaper with I’m sure a lot let’s maintenance in the future. It’s much more energy efficient than heat pump using -10F air!

 

You should actually get significantly more than 150% of the energy usage delivered as heat. If the heat pump is saving you 50% of your energy, it means that it is doubling your energy delivered. (I.E. you get 200%, not 150%.) The ratio of energy out to energy in is normally known as the "Coefficient of performance" (COP). The Wikipedia article on heat pumps (Heat pump - Wikipedia) typicaly lists this as 2 or more for outside temperatures down to -20C. So for 5 watts of electricity, you get 10+ watt of heat.

 

In my case, after three weeks with my Prime Advanced EV range have jumped to slighthly above 30 MPG! I live in Miami, FL and we are having the nice spring weather of this time of the year (average low 70s). I take when Summer gets into the 90s I will see a decline, but so far the battery loves this weather. And it is really 30 MPG, I have a 70 miles daily commute and I'm squeezing those 30 miles, yesterday I got home with the battery at 5% and today I filled-up my gas tank for the first time after three weeks and 2 days!!

 

Congrats !

BTW it should be 30 miles not 30 mpg

 

30 miles of EV.