Many metro Phoenix homeowners likely frowned or grimaced after receiving their latest property-tax bills in the mail.

Property taxes on an average tax bill for a Valley house rose by about $50. That might not seem like a lot, but Arizona homeowners are used to low property taxes by national standards.

And this year’s tax increase and projected future increases were enough for the man responsible for sending  the bills — Maricopa County Treasurer Charles “Hos” Hoskins  — to launch a pre-emptive strike.

With the tax bills, he included a two-page letter explaining that the increase is the result of a legislative and voter-approved proposition that has increased property taxes for homeowners.

He’s talking about Proposition 117, a law passed by 61 out of 90 legislators and 55 percent of voters in 2012, according to his letter.

The law is convoluted like the rest of Arizona’s property-tax system that involves thousands of entities, including counties, schools, libraries, fire, police, water and street-lighting districts levying taxes on property owners. Tax bills lag the valuations they are based on by almost two years, and tax rates don’t rise and fall with home values as many assume.

Implementing Prop. 117 lagged its approval by a few years because it takes a while to change Arizona’s tax system.

I have covered property taxes in Maricopa County for the past decade. Here’s the simplest way I can explain what Prop. 117 will mean for homeowners: higher taxes, and not because schools are asking for more money.

Through a complex formula, more of the property-tax burden is shifting away from commercial-property owners to homeowners.

To be fair, commercial-property owners have carried a higher share of these taxes for a while and still do.