Old Smokey and my old friend Tinny have it right. Sat on the ground with your subscale set to QNH it WILL show elevation above sea level (+15 feet or so - unless the alti is faulty in which case QFE will be no more accurate).
So, can anyone come up with a sensible reason still to use QFE? Unless you don't like having airfield elevation showing when you land 'cos you've lost all the bugs on the outside rim of the alti?