In a house I have in Hermosillo Mexico, a desert area with extreme hot
weather and dry winters, tipically from 40-45C (113F) in the sumer and
nearly 0C (32F) freezing temps, but always below 50% humidity, makes it
mandatory to have an air conditioning systems. My experience about 2yrs
ago: we used to have multi-split AC units (only for cooling) during the
summer and small 1.5Kw ceramic heaters for heating at each of two bedroom
in the winter time.

Last year we replaced the splits AC units for a new ones with heating
capability (heat pump ones) just like the one Bill Dube mentioned. It is a
beauty to see those unit work!  Are very quiet, and realy efficient. We
noticed a significant winter electric bill drop due to less energy
consumption on heating. No gas/furnace is use in MX cause elecricity is
cheaper than gas.

Before installing the equipment, I didn't wanted to have in the roof
without looking inside the units and considering I could have void the
warranty, I decided to open one and see how the thing worked; The
compressor was a 3 phase AC motor technology driven by a 240Vac smart
controller, taking the AC from the utility, making HV DC and then
modulating the right amplitude and AC frequency into the motor for maximum
efficiency. So does the same thing for the outside/inside fans. When I saw
that, I mapped the controller power electronics and came with the idea
that; If I was able to directly feed HV DC power right at the capacitors
bank before converting the DC energy into variable AC, I could technically;
make it work with a HV DC battery or solar array system or at least a
hybrid system during day/night.

That became a personal project to start building but I had to stop it since
I moved to another place. But then I was able to find other systems that
actually are sold just like that: Hybrids heat pumps:

..which tecnically is an all 3 phase driven unit with a step-up DC-DC power
supply (from 20-40V to 300V DC). Awsome!

I also do have an 'evacuated tubes' solar water heather with a 30G thermo
tank, and it works wonderfull for that house. That thing makes the water
boil every single day in a sunny summer day that I have to partially cover
it (no other water heater system is needed for the house needs)

My point of all this is: Maybe PV solar is not 100% efficient, but using
the generated electricity to produce heat on a heat pump system may be as
well as efficient to using direct solar water heating. Just like it was
mentioned before, a heat pump is technically a 'heat exchanger' depending
of the perspective you see it (for cooling or heating) and the energy used
is for the exchange process not to produce heat as resistive heaters. But
solar water heaters are 'Passive' components that may last 10X times that
any heat pump device with actual techology, consume zero energy (other than
the sun) and have zero moving parts.  Both can store energy during the
night and both methods have different applications at different needs.

On Thu, Nov 30, 2017 at 10:26 AM, Peri Hartman via EV <>

> In your case, Cor, I think insulation is the key. If heat loss is minimal,
> the gradients inside will be minimal. Insulation would also make a big
> difference in an EV. But not so easy, perhaps.
> Peri
> ------ Original Message ------
> From: "Cor van de Water via EV" <>
> To: "Electric Vehicle Discussion List" <>
> Cc: "Cor van de Water" <>
> Sent: 29-Nov-17 10:30:23 PM
> Subject: Re: [EVDL] Heat pump vs resistive Heater (never buy another AC
> unit)
> Jim,You perfectly describing the situation where the design of the heating
>> system is inadequate for the building, which typically happens when it was
>> not designed but someone just installed something and hoped for the best.My
>> mom had her house converted to floor heating, which included insulation
>> under the floor. I do not know a house more comfortable than hers, while
>> she has significantly reduced her heating costs. The heat capacity and
>> insulation is such that the house loses only a few degrees overnight when
>> her heater is off. Actually the thermostat is just reduced a few degs but
>> the heater does not come on all night even with freezing temps outside. Our
>> house loses several tens of deg in a few hours...
>> Sent from my T-Mobile 4G LTE Device
>> -------- Original message --------From: jim--- via EV <>
>> Date: 11/30/17  7:19 AM  (GMT+02:00) To: Electric Vehicle Discussion List <
>>> Cc: Subject: Re: [EVDL]  Heat pump vs
>> resistive Heater (never buy another AC unit)
>> Cor van de Water said (in part):
>>> I have always been amazed by how most of USA has forced air blowing
>>> around through their house, which I find
>>> rather uncomfortable. I am from Europe, where you have radiators under
>>> windows that are warmed with
>>> warm water and air in the room naturally circulates at a very low speed
>>> (natural convection) throughout the room.
>> You're entitled to your opinion, but I HATED radiators which were the
>> norm in schools when I was a kid.  You always ended up with the kids on one
>> side of the room frying while the kids on the other side of the room
>> wearing heavy jackets to keep warm.  Same thing with the floor furnace that
>> was in my grandparent's house.  In cold weather we'd all huddle within 10
>> feet of the furnace while the rest of the house was frigid.
>> 73
>> -----
>> Jim Walls - K6CCC
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