p>We would say that to keep a Legalett air heated floor slab operating during a power outage is probably unnecessary unless it's going to be for several days in very low temperatures - as otherwise <a href="/guides/2200/the-pros-and-cons-of-thermal-mass-in-buildings/" target="_blank">the thermal mass within the concrete</a> will keep the room at a stable temperature. Otherwise if it's in an off grid home then we would suggest that the most economical and sensible option is a full solar array for the house's power needs with battery backup - then everything stays running.</p> <p>Regarding the "collector pipe though a wood fireplace" idea, speaking from experience, be careful to not remove too much heat (I've recovered heat going up a masonry chimney stack before) as it can cause issues with the flue draw and condensation.</p> <h3>It's also useful to read our guide on <strong><a href="/guides/3804/how-to-handle-a-power-outage-in-cold-weather/" target="_blank">how to survive a power outage in cold weather</a></strong> .</h3> <p>Hope that helps!</p