BMW i3 REx Review: It’s Brilliant Until You Step On The Gas Pedal


BMW i3

BMW i3

The Detroit Free Press‘ Mark Phelan is a well-respected automotive journalist.  His review of the BMW i3 REx is mostly positive, with statements like:

“In battery mode — which provides a range of 72 miles, according to the EPA — the i3 is a spunky, eccentric and eye-catching glimpse of the future.”


“The i3 is easy to drive. Its small size makes it maneuverable and easy to park. The shifter is not like any other car, but becomes second-nature quickly. The electric motor’s 170 hp and 184 lb-ft of instant torque deliver plenty of power for darting through gaps in traffic and highway driving. The handling is responsive, but less compelling than the BMW group’s other small hatchback, the thrilling Mini Cooper.”

But, in his 3-star review of the i3 REx, Phelan found a near-fatal flaw:

“The ★★★ 2014 BMW i3 electric car performs so much better in its battery-powered mode than when the gasoline-powered generator kicks in to extend the car’s range that testing one is almost like reviewing two different cars.”

“But the extended-range mode that lets you drive beyond the battery’s limit, is severely limited, both in how far the car can travel and in how long it’ll take you to get there.”

Here’s Phelan explaining his time behind the wheel in the i3 in extended-range mode (it’s far from a positive experience):

“With the little gasoline engine generating electricity, the extended-range mode felt no different from battery power driving on surface roads. Fuel consumption was much higher than I expected, though. I refueled early in the 70-mile drive home and had to stop for more gasoline in about 40 miles. Extended highway trips would be unthinkable.”

“Worse, the generator did not provide enough power to maintain highway speeds. Moving with traffic at around 70 m.p.h., cruise control could not hold the speed on slight inclines. The i3 slowed like an overloaded semi in the mountains. I had to pull into the right lane until I reached the top and headed downhill.”

Phelan breifly compares the i3 REx to the Chevy Volt, saying, “The net effect is that the extended range generator should only be used for short distances. It’s essentially for emergency use, unlike the Volt and ELR, both of which deliver more than 300 miles of driving range.”

Phelan concludes:

“The i3’s limited range and highway struggles should disqualify it for buyers who will use the range extender much. If you’re unlikely to go more than 70 miles, it’s fine, but in that case, why not save $3,850 and get the battery-only i3?”

Phelan is not the first (and, surely won’t be the last) to experience the i3’s underpowered REx. BMW will need to rectify this with a larger, more powerful engine/generator (like the Volt) if it hopes to gain more widespread approval of this range-extended version of the i3.

Source: Detroit Free Press

Categories: BMW

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66 Comments on "BMW i3 REx Review: It’s Brilliant Until You Step On The Gas Pedal"

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I saw this coming from a mile away. When I saw that it was just a 2-cylinder motorcycle engine, I really questioned whether it would provide sufficient performance for hills & acceleration. And sure enough, the laws of physics still work.

That said, I still think it is a good system as long as you have control of the ‘hold charge mode’ or ‘mountain mode’ or whatever they call it. Most of the time you will just use electricity so you’ll be fine. If you are going to do a long trip involving hills, then engage the hold mode and you should do fine.

But if you just run-out the battery and then start trying to climb hills just on the gas engine . . . that is not a situation wherein you want to find yourself.

In Denmark it is possible to start the rex, when battery is 75% and gastank is bigger 9 Liter.
It seems They cripple the US version.

Yep . . . the European version is much better.

But by what I understand, it is pretty easy to hack the US version and access the hold mode so hopefully lots of people are doing that.

What I keep wondering is why does a 600cc motorcycle engine only have 28 horse power?

It should have at least 2-3 times that much power, which would make it relatively safe for a REx in the 2,8000 pound i3.

I looked it up and the BMW scooter this motor comes from has 60 horse power. So, why does the i3 REx only have 28? It seems like a colossal safety issue.

Cause they won’t allow it to go into the powerband because they would need a bigger generator and it would also be louder. Im not sure but i don’t think bike engine has to the same emissions standards as a car engine so that why it could be limited too.

The US version was deliberately crippled to try to qualify for the white carpool lane sticker in CA. They negotiated a “BEVx” category for themselves. Then California basically said “ha ha, no, you get the green PHEV sticker instead”.

Maybe BMW will do the right thing and enable hold mode as a user controllable thing, like in the EU, now?

They were fully aware they would not get the white sticker. (And white stickers would actually be a benefit to the customer.)

BMW lobbied for the BEVx category to be created, not for HOV stickers, but for zero emission credits; every i3 REx that BMW sells gives them the same ZEV credits as a BEV i3. And BMW’s explicit argument to CARB for classifying BEVx cars as ZEVs is that the REx mode:

1) cannot be turned on until the battery is drained
2) is so annoying (limited fuel tank, limited power) that no one would use it for long periods intentionally (as opposed to, say, Plug-in Prius owners that literally never plug in at all)

In the U.S., the i3 REx is a compliance car. There really is no other way to spin it.

They have the engine come on when there is only 6% battery charge remaining. Those CARB or ZEV credits must be worth a lot of money to BMW…

I look at it a different way. The Rex only costs $3,800 more than the BEV version and when you are talking about a $40,000 car to begin with, that isn’t much extra to pay. The Rex version has almost no downside worth talking about over the BEV version. And considering around here in Texas we have zero CCS fast chargers, that’s right, zero of them. I think it is well worth the extra cash to get the Rex so that you aren’t stuck for hours at an L2 station somewhere to get home.

There’s 1 in Austin.

Palmer Events Center, 900 Barton Springs Rd, Austin, Texas 78704, United States

people expect so much, 30 year ago a compact car was a shit boxes! now, heated seats,7 speed auto ,super fast acc.a very small something to give up and bam!no way man i am not going two a slow car for a second,and yes only a few min a year more two save 6to 8 tons of co2.make a law .walk or drive electric .(wow what a great car i didn’t have to walk !it depend on the angle you look at.yes i have to stop to charge once here and there but for pete’s sake we saving the planet one car at a time.way better than the shit that use gas and take 2-3 grands a year ,year after year!

Depends on your goals. I you are looking to primarily cater to eco-buyers, then, sure, they are willing to make those kinds of trade-offs to save the planet. If you are looking to create a car that has mass market appeal (and saves the planet as a happy side effect) then it needs to compare favorably against the cars its going to be cross-shopped against–and in the $40K segment, that is a lot of cars. Based on the amount of R&D BMW invested in the i brand, it would see they are hoping for mass market success.

Personally, I think they should stop trying to game CARB and focus on delivering the best driving experience.

Well . . . I can understand people having expectations for $43,000 BMW.

The thing that bugs me about the BMW i3 granted I did ride in it as my first electric car.

The flaw in it is it’s low range at 83 miles and yet has a battery pack that is a little bit smaller then the Nissan Leaf. But the car is double the price of a Nissan Leaf and triple the price of a Mitsubishi i-miev.

The one thing Tesla has at least shown us with their new solar battery system is that 10 kilowatts of battery power would at least work out to $3500.

In theory if BMW i-3 budgeted $6000 away from the hefty mark up of their car to adding a 35 kilowatt or 40 kilowatt battery they could raise the car’s range a good chunk.

Well . . . I wonder how much that Carbon Reinforced Plastic (CRFP) stuff costs BMW. I know they worked hard on reducing the costs. But I suspect that no matter what, that carbon-fiber stuff is a bit expensive.

The whole CFRP thing really surprises me. The i-MiEV and i3 are similarly-sized vehicles, yet the all-steel i-MiEV weighs less. Granted its 16kWh battery pack is smaller than the BMW’s, but I would think BMW could make their vehicle lighter without exotic materials.

The i3 REx is an amazing car if you’re comparing it to everything available in 1985.

Unfortunately, if you’re comparing it to everything available in 2015… not so much.

No, no, no. BMW does not “need to rectify this with a larger, more powerful engine/generator (like the Volt) if it hopes to gain more widespread approval of this range-extended version of the i3.”

The answer is in the car itself. It needs to rectify it with a larger capacity battery, a massive deployment of CCS stations and no stinky, noisy, vibrating, and pathetic gas engine whatsoever.

If They use Tesla battery density, they would more than double the range, that would be cool
BMW W·h/kg 95 Tesla W·h/kg 235


The eternal Sophie’s Choice of the BEV purist:

When you’d prefer that consumers purchase an ICE car because BEV battery range and charging infrastructure is insufficient, than purchase an EREV that drives on electricity the majority of the time but has a gas engine attached.


Yes, because the fact remains that if we have gasoline “charging stations” everywhere, why would anyone bother to build out DCQC infrastructure?

There’s a big difference when you’re asking The Powers That Be (be that your electric company, your government, or your automaker) if they can please install a DCQC in location X so you can reach destination Y from point A, and asking them to install one at X because it would be nice of them, and cheaper for you. But they don’t have to, because “you’ve always got that gas backup”.

Which infrastructure are we fighting for, anyway?

DCQC is utterly irrelevant for 90%+ of EV miles put to the ground, so I’m not sure where you’re going with this. Outside of free, subsidized DCQCs (which are not a long-term solution), commercial DC charging costs are so much more than home charging costs that no sane person would use them except when absolutely necessary to complete a trip.

In the interests of saving time, please make sure that any response you offer about DC charging costs does not lean heavily on a car with an average sale price of ~$90,000. You can buy an awful lot of kWh with that kind of money.

The i3 represents what the Germans do best, which is to brilliantly implement fundamentally bad strategies. LOL

Boy, you hit the nail on the head with that one.

Brilliantly put!

A bigger battery would be better, but just switching to the European software for the REx control would go a long way. The European version allows the generator to kick in much earlier. Bad move on BMW’s part to cripple the US version. They deserve the bad press for this bad decision.

Wasn’t that decision driven entirely by CARB?

Not really. BMW specifically lobbied CARB to create a new classification of vehicle (BEVx) that cannot activate the engine before the battery is drained and has less gas range than battery range.

This category currently exists of exactly one vehicle: the i3 REx. And no other manufacturer has plans to make a qualifying EV.

This isn’t just a case of you made the bed, now lie in it. This is a case of you designed, manufactured, distributed, bought, and made the bed.

I’m calling BS. Michigan does not have sustained elevation increases on any stretch of any highway in the state sufficient to cause the i3-REx to experience the performance limitations that people in mountainous states have seen. That is, unless he was out of Michigan when he gave his review. 😉

Also, the REx is not a problem outside of the US because those cars don’t have to reach a low SOC before the genset can kick in. Stupid government regulations have caused this problem.

Not sure how much of an incline you need to experience the problems in the i3, but Michigan does have hilly parts, and several ski hills. (not just the ones on landfills in the Detroit area)

Stupid regulations that BMW lobbied for! BMW wanted the EV rebates and white stickers even for the REx, that’s why the BEVx category even exists. If they had settled for the green stickers and EREV category, then they wouldn’t have this image problem:

So not primarily CARB’s fault.

I don’t think that’s quite true; BMW knew that that the white stickers were a long shot, and essentially abandoned that plan early on.

The real reason the REx is crippled is so that BMW can get full zero-emission manufacturer credits for every i3 REx sold. That’s why BMW lobbied CARB to create a “BEVx” category (which only affects ZEV credits, not HOV lane access).

If the BMW i3 REx in gas-powered mode loses speed when going uphill, that means it’s rather limited in other situations where you need prompt acceleration, too. Such as passing on a two-lane highway, and in merging onto a freeway in heavy traffic.

Presumably those situations do occur in Michigan, even if it actually was as flat as Western Kansas… which of course it’s not, as shown in the photo below.

Also, people from one state do occasionally move to another. Most people would like their car to function on roads around their new home just as well as their old.

The charge sustaining mode power limit only occurs during sustained power demands.

If you need to pass someone, you’ll be doing that out of the 6% buffer the REX maintains in the battery.

Sadly, reviews written by those who have actually driven the car don’t agree with your assessment.

For example,’s review says “When the battery is depleted and the i3 REX relies on the generator, the 0-60 time slows dramatically [from the Edmunds-measured 6.6 seconds] to 13.7 seconds.”

As Speculawyer said above: “And sure enough, the laws of physics still work.”

Yes, the laws of physics are not merely somebody’s opinion. They represent the way the universe actually functions. If the power of the tiny gasoline motor isn’t sufficient to push the car down the road at full highway speed, then the car will lose something from top speed and acceleration, even on a level road… let alone going uphill.

Not opinion, Nick. Reality.

I think Nick is right, as long as you set the conditions appropriately:

The REx will turn on at ~5% battery SOC remaining. Now, if you should happen to need to pass someone immediately after the REx turns on, you’ll have enough juice in the battery to complete your pass at speed, so you’re fine.

If, however, you’ve already been driving highway speeds on the REx for the last 30 minutes, your battery is likely a lot lower than 5% and the REx is struggling to tread water. In that case, if you were to try to pass, you’re probably in for a rude surprise.

At a very minimum, this car should have a “Propulsion Power Reduced” message when the REx is unable to charge the battery back up to 5%.

I view this not as a problem of the rex – rather, it’s the mentality of us. Yes, once in a while, we do have the needs to go to far away places. That’s what the rex can help – in that emergency (which is the opposite of Volt’s ideology – to drive as much and as far as you like: freedom). But on an almost daily basis, we don’t. Now, rex crowd will usually say, “but I need to make such and such trip after work, to visit this and that person.” Well, do we REALLY need to make that trip? Of course, if you have to take care of someone because of health condition, that’s another thing – but how many of those are we going to get? And with all the technologies in our “hands,” can’t we just do FaceTime, instead of driving? But we keep telling ourselves, we MUST drive. Mind you, that trip – the freedom – comes with a lot of adverse effect to us and to the environment – pollution from exhaust, causing additional traffic jam, burning up more fuel and energy, requiring more oil changes, lost time stuck in traffic, etc. For… Read more »

‘The problem is who’s going to buy a $45k compact car’

NO ! The Problem Is:

Who is going to pay $60,000, which includes tax and license for the “REX” in California,,,,, for a plastic golf cart that can’t get you up the hill to the next Tee,,,after the 9th hole???

But,,,wee is it fun on the Fairways!!!

Please try to stay on topic of this article, which is about the up/down sides of the rex.

The article is NOT about the sales number or price of the vehicle itself.

But just to entertain you 2, you are right about the high price too, similar to the VOLT price article. BMW loyalists will buy it, but that’s a small subset of BMW sales, as reflected by comparing i3 sales number to the luxury brand compact sales number as a whole.

“Also, the REx is not a problem outside of the US because those cars don’t have to reach a low SOC before the genset can kick in. Stupid government regulations have caused this problem.”

You mean, stupid regulations which BMW lobbied hard for the State of California to create, so it could have a special category of EV (“BEVx”) in which to earn more carbon credits than the i3 deserves.

In this case, it’s not the bureaucrats nor the politicians who are to blame. It’s the auto maker, BMW. This was their choice.

After reading some of the more recent comments here…

If Spider-Dan is correct in what he says above, that BMW had to cripple the REx version just to get the same number of carbon credits with that version of the car as with the pure BEV version (no range extender), then I’m wrong about the counterproductive CARB regulations for CARB’s “BEVx” category being BMW’s fault. If Spider-Dan is correct, then the fault rests entirely with California’s CARB agency. There is no logical reason that adding a range extender to a BEV should result in a reduction in carbon credits.

However, it’s not that simple; in the real world, things often don’t follow logic. I note that the EPA rates the REx version as having a smaller all-electric range. Apparently that’s more because the gas motor kicks in when the battery reaches about 6-7% state of charge, and less about the added weight of the REx generator. Given that reality, the REx should yield slightly lower carbon credits than the pure BEV version, but only slightly.

I think there’s a very logical reason for the BEVx category receiving full ZEV credits, and I don’t fault CARB at all for creating it, given the restrictions they applied.

The fact that the REx cannot be engaged before the battery is drained, coupled with the fact that the REx range is necessarily horrible, means that the REx is used specifically as an emergency range extender.

In practice, this means that interested customers who would have to disqualify the BEV version (in favor of an ICE or PHEV) can actually consider the i3 REx. The impact of driving a somewhat-longer-range EV most of the time is, I believe, significant justification for the carbon credits.

I think this logic is not too far removed from the justification for letting PHEVs have green sticker HOV lane access: they probably aren’t going to be running on battery when actually using the highway HOV lanes, but the carbon savings from all the other driving they do is worth it.

I was definitely one of the people thinking that GM should have put a smaller engine in the Volt once upon a time. I stand corrected! Big hit in performance and hardly any more fuel efficient. Maybe somebody will come out with a highly optimized range extender some day, but it seems likely to me that Gen 2 Volt is probably as good as it gets for fuel economy in a mostly series-hybrid vehicle.

I susect the lack of fuel efficiency is due to the serial design.

I don’t want to get into whether it is BMW or CARB to blame for the artificially crippled mess that has been made out of the US version of the i3 REX. What matters is that they need to sit down and get together and fix it! Step 1) Start with the quickest and easiest solution first, which is to update all US i3 REX’s to the same software they have for the rest of the world. That will greatly improve the safety aspect, without drivers having to hack their brand new $40-50K car, and hopefully BEFORE people have to die in a failed passing maneuver where they lost power. Do it through a recall immediately — Safety First! Forget about any whining or crying about ZEV credits this, or ZEV credits that. I’m absolutely certain that even the CARB Board members put safety first over whatever ZEV credit issues that might need to be worked out. Step 2) Re-write the BEVx classification. This version failed. There certainly IS a market for charge sustaining, and even charge depleting BEVx vehicles (When Done Right). And these vehicles certainly can be built in a way that they use very little gas, much… Read more »

BMW obviously cares a great deal about those ZEV credits or they wouldn’t have lobbied CARB to create the category in the first place, so your solution essentially has to start and end with convincing CARB to eliminate that category.

If, somehow, BMW could be convinced to forgo ZEV credits on the i3 REx, then CARB doesn’t even need to get involved: BMW announces that new i3 REx units will no longer be crippled, problem solved. (You won’t see BMW fixing existing i3s, as that would likely involve returning credits they’ve already received.)

But given that BMW is primarily a manufacturer of luxury vehicles, it seems to me that they need every ZEV credit they can get… which is why they were willing to sacrifice the U.S. i3 REx to begin with.

Oh geez… I should have read this before doing 248 miles on the REX only, in frigid cold, driving 65-70 mph. Without any problems.

And why are digging up these old stories, looking more clicks?

The stories are needed to make sure that everyone knows what a bad car BMW made for the US.

Bad BMW, bad boy.

Sorry, I think my i3 is great… But then again I don’t have the urge to drive over 80mph…

I had a 370Z before and I didn’t have that urge either.

Lol. Like a reviewer from the Detroit Free Press is an impartial and fair judge of Detroit competition.

I really like the i3 rex and am considering replacing my Volt with one this Summer when my lease is up (especially now that I see that Volt 2.0 won’t be available here in Texas until (likely) Thanksgiving. However, two weekends ago we drove down to see some Bluebonnets and put about 180 miles on my Volt that day. I was keenly aware of the multiple fillups that would have required in the rex.

This past weekend we drove to Austin (200 miles South – one way – plus driving to the hill country, etc.) for a wedding in the Hill Country outside of town. The i3 would have been a serious pain in that situation. Filling up 7+ times (depending on how close to “empty” I was comfortable getting in the Hill country) would have been painful. We drive to Tulsa next weekend for a graduation.

Finally, I actually started contemplating making our Austin trip in an 85 kwh Model S and EVEN THAT gets dicey given that we rolled into town and had to head to the Hill country and got back late. Searching for a charger would NOT have been fun.

None of this is new. All these i3 limitations have been known since day-one. And they could be minimized quite simply with a “mountain mode” and bigger gas tank. But BMW will not change the design.

That’s why (once again) the i3 is a great in-town EV, but a pretty lousy EREV.

I don’t agree and I have the real life experience with it.

People need to calm down about BMW. In fact, all BEV purist should thank BMW for making the REx so terrible. It will just push more people driving on EV mode only. Not to be picky, the i3 REx is really a BEVx NOT an EREV like the Volt. Please spare me the arguement of those terms… They are important to distinguish for exact this reason. i3 REx is BEVx where its EV mode is far superior than its “crippled” REx mode. Volt is an EREV where its EV mode is no compromise full EV mode and neither is its REV mode. Prius Plugin is a weak PHEV. All of them can be considered as PHEV as pure defintion but the subset seperation is important to distinguish the difference. Personally, I think i3 REx is fine. It is NOT designed to go long distance as the Volt. It is designed to limp to the next charging station. That is why i3 REx comes with DCFC option and Volt doesn’t. That is why Volt has Hold mode and larger tank and i3 REx doesn’t… Call it tradeoff and choices for buyers to select. Don’t try to make all choices the same.… Read more »

ModernMarvelFan said:

“Not to be picky, the i3 REx is really a BEVx NOT an EREV like the Volt.”

To be picky, the i3 REx actually does fit the literal meaning of “extended range electric vehicle” (EREV), unlike the Volt… which is a fully functioning PHEV, despite GM trying to paste the misleading “EREV” label onto it for wrongheaded marketing purposes.

I keep seeing this fight in these forums about why the Volt is not an EREV. It must be because there is no generally accepted definition. I tried looking this up and either it means all electric untill there is no charge and then runs only in serial mode, or a vehicle that is full performance as long as there is charge and has a backup energy supply that is used only when there is no more charge.

Volt would not fit the first definition but would fit the second one. i3 Rex would fit both.

If someone says the Volt is an EREV, just assume they are working off the second definition. You know what they mean. It is still a useful term to differentiate it from a Plug in Prius type vehicle until there is a better vocabulary out there to describe what the Volt is. Honestly, when the gas engine is running in either a Volt or i3 Rex, does the typical driver really care how the power gets to the road?

I’m still not sure why people care if a vehicle is serial or parallel when running on gas. Gas-powered is gas-powered; if Toyota releases a new car tomorrow that runs entirely as a serial hybrid, that car is no more an EV than the standard Prius of today.

It is semantics, but calling a vehicle that has a part-time direct connection between the ICE and the wheels an “Extended-Range Electric Vehicle” just feels wrong.

Just returned home from a 117 mile drive across the Los Angeles basin. Drove on a combination of battery and REx. When the REx kicked in, I drove at freeway speeds of between 68 and 75 miles per hour without a hitch. It is true that if I had to drive a steep incline or hill on the REx I would experience “the great slow down”, but my freeway drive doesn’t include hills. I take this drive twice weekly. No trouble getting home comfortably without worrying about range. The i3 REx is precisely what it is as advertised and as such, a terrific vehicle–fun to drive, fast off the mark, taunt, a turning radius to die for and a comfortable, spacious interior. If you want a car that takes you from the “burbs” to the city as a daily commuter or for occasional trips, the i3REx has no peers.

1+ And confirmed, I have the same pleasure driving this car and I feel the REX is crippled, it does what it was intended to do and does it well.

not eye catching in a good way

As an owner of the Rex, I would say that it is essential in the UK in late 2014 and 2015. I would also say if your commute is more than 60 miles round trip, or 120 miles if you can charge at work then this is not the car for you. This is a fit for purpose view point. I will continue by saying I love the car, it was the right choice for so many reasons. I do the occasional long trip. 180 miles one way, or a longer day out. For this Rex is required, I can’t be stopping for hours for a charge and all to often the motorway chargers are not working. In the UK you can turn Rex on when you want, so I simply top up with fuel and turn Rex on when that happens. Unlike the US the car retains the charge more or less at motorway speed 70mph. On longer climbs it drops a bit, but because I anticipated this I still have full function of the vehicle. When the range is 4 miles more than the distance to may destination off goes Rex. Again, UK weather, this has never been… Read more »