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Independent testing shows 21.2% reduction in fuel consumption with XL Hybrids retrofit system

The XL Hybrids system in place. Click to enlarge.

Testing at an independent EPA-certified vehicle laboratory showed a 21.2% reduction in fuel consumption achieved with XL Hybrids’ aftermarket hybrid electric powertrain (earlier post) on a light-duty cargo van on the UDDS cycle (urban conditions). The company had been targeting a 20% reduction.

The tests were conducted on a light-duty chassis dynamometer test cell featuring a twin-roll Clayton dynamometer. The testing process compares fuel economy performance from the vehicle in its original condition with the performance using XL Hybrids’ charge-sustaining hybrid system. The test was completed using a Chevrolet 2500 Express cargo van fitted with the original equipment manufacturer’s 4.8L engine and 6-speed transmission.

XL Hybrids’ hybrid electric powertrain is a low-cost, low-risk, bolt-on, post-transmission parallel hybrid technology designed for Class 1–3 commercial vehicles that integrates seamlessly with the conventional internal combustion engine and transmission. The current 2012 powertrain consists of a 2 kWh lithium-ion battery pack, a 40 kW (53 hp) electric motor and a proprietary hybrid control system that operate with the OEM internal combustion engine and automatic transmission.

Integration of the XL Hybrids (XLH) system is right at the tail housing of the transmission. XLH removes the stock tail housing, and replaces it with the XL system with integrated electric motor. There is no removal of major components of the OEM powertrain, notes Justin Ashton, co-founder and vice president of business development.

What’s unique about our system is that it’s bolt-on—we don’t have to modify the ECU or the TCU. Our hybrid controller connects to the CAN; our controller is read-only. We listen to CAN, collect signals. That totally gets around the problem of having to create a whole new set of controls for the engine and transmission. It also doesn’t necessitate a recertification of the vehicle for safety, emissions.

The underlying internal combustion engine is unaffected because of how we integrate with the vehicle. We don’t touch the warranty. Our own components have a 3 year, 75,000 mile hybrid system warranty.

—Justin Ashton

This year, the company will release between 30 to 50 fleet trials, Ashton told Green Car Congress, using the 2012 system. XLH engineers have already designed the next-generation release, in which the battery pack is downsized to 1.5 kWh, Ashton said. Both the 2.0 kWh and 1.5 kWh packs were in essence “off-the-shelf”—i.e., already developed for an OEM and sold worldwide, to reduce XLH’s engineering costs.

The current 2.0 kWh pack sits inside the vehicle; the 1.5 kWh pack is intended to fit between the frame rails.

From a higher-level perspective, what’s important to customer is the benefits of fuel consumption reduction, as opposed to what the technology is. OEMs can get higher mpg improvements by using different architectures. Our focus has always been from day one to be cost-effective. We rely on customer interest for the ROI threshold. They’ve told us if you can get this to an under 5-year payback, then we can talk.

—Justin Ashton

The planed price for production in 2013 for the full release system is starting under $8,000 including installation, Ashton said, with fleet discounts beyond that. The system is designed to be installed in about 4 hours, faster at a commercial upfitter.

In May, XL Hybrids signed an agreement with Henley Transmission Services, LLC, the largest franchise holder of AAMCO automotive service centers, to certify AAMCO technicians to install and service XL Hybrids’ hybrid-electric conversions.

XL Hybrids was founded by MIT alumni and is based in Boston.



Assuming the 20% fuel reduction goal as a good ROI, this EPA rated 21.2% bolt-on fuel reduction seems a good fleet buy.

Dave R

Just looking at simple economic payback - the example cargo van gets 15 mpg EPA combined (13 city, 18 hwy). Assume the van is driven 20k miles/year and gas is $4/gallon, they will save about $1k/year on fuel.

For high mileage fleets or fleets driven in heavy city traffic, it makes sense on a pure ROI investment, not to mention all the side-benefits of reducing fuel consumption.

I would still love to see this available as a plug-in with even just a nominal boost in efficiency - even a 5 kWh pack charged multiple times a day could be beneficial with minimal additional cost to the system. Key would be to use this in fleets where multiple daily charges are possible and to be capable of 240V-30A charging so it can charge from empty to full in ~30 minutes.

Nick Lyons

Very cool: a retrofit that pays for itself in under 5 years. This should be a no brainer for very high-mileage fleet vehicles.


I tried to figure out how it works. The XL website says it uses regen braking which makes sense, this would be activated by the brake pedal signal.
Then they claim it (helps) "propel the vehicle when drivers accelerate" and this would probably be activated picking up by the gas pedal or throttle signal. The oem engine management software would have to lighten the fuel boost when e-boost kicks in--this is plausible without tweaking.
I would anticipate some driveability issues like rough transitions. Also it seems trouble is likely with antilock braking and traction control systems.


I would think the OEM engine management software would "not care" about such a moderate hybrid addition, as the SW now ignores cargo weight, incline (uphill or down), braking level, etc.

But what is the cost?
The planned price is "starting under $8,000 including installation".

I expect the independent EPA-certified vehicle laboratory calculations can show the price is even less.


Here is the challenge for this business model: the challenges of achieving scale. The component cost at scale is $1000, such as in the Chevrolet Mild Hybrids. So it's the problem of designing, building and selling the first 10,000 units that drives the installed cost up to $8000. 8 year/150,0000 mile payback is not a great value prop. 5 year/100,000 mile payback (if the cost were $5000 installed) is a great idea for many businesses and owners. At $3,000, you would simply be stupid to not do it. That's why it would be so great to get Ford to do mild hybrid on the F-150....imagine getting the largest selling vehicle in the US to go from 18 MPG combined to 22 MPG.....


Fleets will pay a lot less, and save even more if they use their own mechanics for the conversion. How much would it cost as a factory option is the interesting part.


Wait - Using your figures, passenger cars and small SUVs (with an bigger market to sell in) would be an instant winner.

Smaller batteries, lighter weight - WOW.

Someone should make one.

Why has no one thought of this?


TT, eAssist is even cheaper


That's why it has taken over the market.

Calvin Brock

There is no removal of major components of the OEM powertrain, notes Justin Ashton, co-founder and vice president of business development. Sección Amarilla

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