Got a letter from Spark inviting you to ditch your copper phone line for the company’s wireless network? You’re not alone.

Several Consumer members have contacted us, puzzled over letters, phone calls or door-to-door sales reps urging them to swap from copper to Spark’s wireless 4G network.

The company says copper lines are becoming more unreliable and fault-prone, especially in wet weather. “Water and wires don’t mix,” Spark claims. Switching your phone and broadband to wireless will give you “a reliable and fast connection”.

When we rang Spark’s call centre, a sales rep said its wireless network was just as good an option as VDSL – phone and broadband provided via the copper network.

But the facts are:

It’s slower: Expected fixed wireless speeds range from 10 to 40Mbps (megabits per second) while VDSL speeds range from 20 to 55Mbps (with possible speeds of up to 70Mbps depending on your distance from an exchange).

It’s prone to congestion: As more users are added to a wireless tower, the service will slow, particularly during peak times.

It’s capped: The most data you can get each month on Spark wireless is 120GB, while unlimited ADSL or VDSL plans (both provided via a copper line) are readily available.

In our view, wireless is unlikely to be the best bet for many people wanting a “reliable and fast connection”. If you get sub-par mobile coverage where you live, the odds are wireless broadband reception will also be ropey.

For more about broadband speeds, see our report on getting faster internet.

What’s happening with copper lines?

The copper network isn’t disappearing anytime soon. The Commerce Commission will review the network between 2020 and 2025. During that period, Chorus will only be able to withdraw copper services where fibre is available.

In 2016, there were 1,176,000 copper line connections. Chorus reported 35,084 faults on the copper network in August, equivalent to 3% of connections for the month.