Windows tablets hold within them an implicit promise: To deliver the full Windows 8 experience in a svelte tablet form factor.

Unfortunately, the ambitions of Microsoft and its partners have thus far exceeded reality, largely due to processor power issues. Even the lowest of low-wattage Ultrabook chips simply sip too much juice, forcing manufacturers to house their hybrids in cases full of fans—a compromise that has left Windows tablets and convertibles thicker and louder than the ARM-based tablet competition.

No more. Intel announced Tuesday that new Core Y-series Haswell processors capable of fitting in thin, completely fanless designs are inbound “in the coming months.”

While Intel had previously announced its Core Y-series chips would run at a scenario design point—basically, an Intel metric for the power draw during sustained workloads—of 6 watts, the newly announced processors will dip all the way down to 4.5W SDP. (6W variants will also be available.) That 1.5-watt difference between the two is the difference between needing additional cooling and a potentially fanless design, according to Intel

”I think there is a real market need for a fanless tablet or 2-in-1 with PC-level performance,” says Moorhead.

Tablets and hybrid PCs with the 4.5-watt Core chips will offer more than nine hours of battery life on active usage, Intel spokesman Dan Snyder said via email.

Don’t expect to see crazy performance from such low-powered Haswell processors, however.

While the new chips will be able to boost to higher performance for short periods thanks to their 11-watt thermal design power rating—a “worst-case” power metric that measures the maximum energy used during heavy workloads—a large part of Intel’s ability to bring the cooling and power requirements down so far lies in underclocking the processor. Sustained boosting above 4.5W would strain the cooling capabilities of a fanless chassis.

Even still, a low-powered Haswell processor will blow the pants off both ARM chips and Intel’s own Atom CPUs, performance-wise, bringing true Ultrabook-like chops to a truly tablet-style design.

PCWorld (US) Intel’s Haswell-based hybrid reference design, as shown at CES 2013. It’s skinny.

“I think there is a real market need for a fanless tablet or 2-in-1 with PC-level performance,” says Patrick Moorhead, president and principal analyst at Moor Insights and Strategy. “This is exactly where Intel’s new 4.5-watt [chip] comes into play… Even though the 4.5-watt Haswell will be clocked lower than the 6-watt version announced at Computex, it will have significantly higher performance than Bay Trail.”

While Moorhead expects production of low-watt chips to ramp up sometime in 2014, Intel says the first round of energy-sipping Y-series processors will be produced in limited quantities. It’d be a shock if those chips failed to show up in a Haswell refresh of Microsoft’s Surface Pro tablet.

Agam Shah of the IDG News Service contributed to this report.