The older mobile homes aren't as tight as the newer ones (say after 1985). They are insulated quite well but again, this can vary by brand. If the mobile home is freestanding (not on a foundation), skirting can help keep the inside temperatures MUCH warmer.   My mom's small double wide mobile home (approximately 900 sq. feet) was heated with natural gas and ran $49.00/month on the budget plan. She often received a refund at the end of the year for over-payment. The mobile home was located in the northeast part of the United States where winter weather runs from November to March. I think I pay that much for heat in 3 days (ok...kidding but HOLY COW...that's a REALLY inexpensive heat bill)!

I personally don't like mobile homes in the summer. They are heat magnets and unbearable without multiple fans or AC.

Michelle