David Fickling, Columnist

You’re Putting Too Much Solar on Your Roof

A solar system should be a good fit, not based on profit-and-loss projections.

Photographer: Brendon Thorne/Bloomberg

How many solar panels should you be putting up on your roof? The question is surprisingly complicated.

The roughly 95% decline in the cost of solar cells over the past 15 years has been so precipitous that the modules themselves are a barely significant share of what you spend.