This is something to consider for when you loose your heat in your house for a few days. You don't want to freeze. A tent in one room for the family could save a life! BUT adding a couple of heating pads take very little power (each about 25 watts) for a night and then using solar to recharge batteries during the day is an ideal solution. Just another TekBit.

When using solar there are two things to watch out for. 

12 volt off the shelf specials at your local big box stores are very costly for what you get (even when on sale). They are also flimsy and of poor quality AND usually have a short life! Roof top and even RV systems are very rugged and usually have a 20-25 year life! About 4-5 times longer! So in the long-run they are really less expensive!