First cost versus whole-life cost
Metal costs more to install than composition shingle, and that is where most comparisons stop. But a shingle roof in this heat is often replaced two or even three times over the life of one metal roof. Add up the tear-offs, the dumpsters and the disruption, and the gap closes quickly.
The Metal Roofing Alliance, a trade coalition of manufacturers and installers, makes this argument in its literature, and on the whole-life math they are right.
Energy
A reflective metal finish bounces a large share of summer sun instead of soaking it into the attic. In a valley where air conditioning runs from May to October that shows up on the electricity bill every month. Shingle in a dark blend does the opposite.
Cool-roof pigments are available in most colors now, so you do not have to pick white to get the benefit.
Insurance and resale
Some insurers offer a reduced premium for a non-combustible roof, particularly in the foothill areas with wildfire exposure. Ask yours. On resale, a long-life roof that a buyer will never have to replace is a real selling point and shows up in appraisals and inspections.
A shingle roof at year fifteen is a negotiating point against you; a metal roof at year fifteen is a feature.
Maintenance
Metal does not shed granules, curl or crack. Maintenance is keeping debris out of the valleys, checking sealant at penetrations every few years, and replacing any exposed fastener washers as they age. Compared with the annual patching an aging shingle roof needs, that is very little.
Standing-seam systems with concealed fasteners need even less.
How to run the numbers for your house
Take the metal quote and the shingle quote. Estimate how many shingle replacements fit into the metal roof's life in our climate. Add a rough energy saving per year for metal. Consider whether you will be in the house long enough to see the payback, or whether the resale value carries it.
I will not put figures on this page because they change with every house and every year, but I will happily work through them for yours.
Where metal loses
If you are selling within a few years, the buyer pays for the long life and you paid for it, so the math only works if the price reflects it. If the neighborhood rejects the look, resale can suffer. And a cheap metal installation by a crew that does not know the material can leak at the seams and cost more than any shingle roof ever would.