It may not be unique but a feature of Mitsubshi,s  (the maker of minisplits that keep heating down to -18f)  ERV is a built in "bypass".   In 'bypass mode'   the incoming ventilation air does not go through the heat/moisture exchange core.  The explanation is that the cooling system can be helped with 'normal ventilation when the outside air is cooler than the desired temperature thus saving energy.  Similarly heating will be aided in 'bypass' mode if the outside air is above the desired room temperature.  I can see where some energy could be saved but! 
How much?  Note that when bypass mode saves is when the heat pump has it's highest COP, probably 6 or more.
What is it worth?
In my mind the Mitshubshi ERV is a looser because it is an energy pig drawing 810  to 1290 watts to move 300 CFM (it uses 2 fans & motors).    Renewaire uses the same 'cores' and offers the lowest energy use (69 watts to move 200 CFM in the EV450 ECM version).   But the Renewaire doesn't offer 'bypass mode'.   At 200 CFM The Mitsubshi would use 4730+ KW / year while the Renewaire uses 604.  4126 KWhr is the annual energy penalty for built in bypass mode.   I do see a way of adding external "bypass" to the Renewaire.  It would require cutting another hole in the case, thus voiding the warranty, an external damper, a tee, and some duct. 
Should I?

It looks like the largest Mitsubishi ERVs draw up to 1290 watts, but they also move a heck of a lot more air - more than 1200 cfm. The smallest Mitsu ERV moves in the range of 300 cfm and draws 278 watts, which is less than the Renewaire's EV300 315 watt draw.

The EV450 (ECM) you mention is classed in commercial ventilators and may be evaluated differently. I am also wondering about the upfront costs to a "commercial" ventilator for residential use with an ECM option.


I have a Recoupaerator DX200 which does have a bypass mode and uses an ECM motor as standard. We use the bypass mode to bring in cool night air in order to flush residual heat collected during the day in our passive solar. It's hard to imagine that minisplits, even operating at a COP of 6.0 could do any better since they would be actively removing heat, while the bypass mode just moves air. Wonder if anyone knows about that.

Am also curious about the performance curve on the EV450 which shows power usage of approx 1 watt/cfm at standard rating points, but seems to be extrapolated to show extremely low usages at lower air volumes. For example 69 watts at 285 cfm, then it jumps radically upwards to 308 watts at 333 cfm. Do you know what that is about?

You'll need to research local weather conditions before deciding on bypass. My minisplit running full time on dehumidify barely keeps humidity in the acceptable range (<60 percent). Not surprisingly, night time flushing doesn't work here even when air temps have been in the 60s in recent weeks. The UP won't be as sticky as the midatlantic, one guesses, but it probably isn't as dry as ICFhybrid's western wash either. UCLA offers free software that downloads weather data from the nearest NWS station and crunches it for you. Google Climate Consultant and HEED.

ICFhybrid.
       The Renewaire EV450ECM's performance includes a colum "ESP" external static pressure AKA duct friction.  The 333CFM is at 1.25" water column of static pressure some thing that never should be seen but it does deliver the air at a cost of 308W.   A little further down is 450CFM @ 0.16"WC which takes 305 watts.  Even though it's commercial it is competitive at roughly $3000.   Being sized as it is it encourages large ducts (10"round) which mean low losses as installed.  On your system, how is bypass mode selected?

I found the information needed to justify,or not, bypass mode.  Let's assume 200CFM and a 10 degree temperature difference, that means 2160BTU/hr is being carried by that airstream.  Since normal mode would be adding that to the heat load and bypass mode instead subtracts from it the difference is 4320 BTU/hr. =1266 watts.  With a COP of 6    211 watts would be used to make up for the lack of bypass mode.   A highly optimistic assumption would be that such gains from 'bypass mode' occur 10% of the time or on average 21wats is the bypass advantage.   Nice thought just not worth much, under $20/yr @ $0.10/KWHr.  Also 1/2 the benefit of bypass mode can be had by shutting down the ERV when conditions are 'upside down'.


  

On your system, how is bypass mode selected?

"EconoCool" operates automatically at a temperature you set on the unit. When the incoming air stream reaches that temperature, energy recovery ceases and the unit just moves air. A remote switch enables or disables the sensing function, so you turn it on when it is warm and off in winter. We use it about five months a year to help remove heat and bring in filtered air. The alternative for us would be to open windows and that increases the allergens.

You can't ignore humidity, Liebler. If you exhaust air at 70 degrees and 40 percent RH and you introduce air at 60 degrees and 70 percent RH, the latent heat load is about 7 btu/hr per 1 cfm of air movement, or in your example, 1400 btu/hr for the phase change back to liquid and to 40 percent RH. The ERV won't intercept all of the excess humidity, of course, so you'd look at the difference. In a supertight house, humidity is problematic just from daily living.