An extremely lightweight and compact heating system greatly increasing patient mobility is provided. The use of a flat plate can be used to greatly decrease package size and weight while providing comparable heat transfer by exploiting the ability of the dialysis bags to conform to this surface and through the greater heating area possible with the flat plate design. A short rim around the plate provides centering and protecting against minor leakage without substantially increasing package height. Protection against leakage is buttressed by sealing the rim to the plate and the use of 12 V only within the heating unit. The result is a lightweight warming device with a short that can be easily transported by the patient greatly improving patient lifestyle and freedom.