More efficient conversion of sunlight electricity doesn't mean the cells are cost effective for putting on a house. On a luxury car like this, area is constrai

More efficient conversion of sunlight electricity doesn't mean the cells are cost effective for putting on a house. On a luxury car like this, area is constrained and money is no object, so it may make sense to use otherwise prohibitively expensive cells to win a few extra percent efficiency. Similarly, such multi-junction cells are used on spacecraft, where the lower mass per watt makes it worthwhile.