For Q1 2026 we crunched the typical real-world delivery percentage of the biggest ISPs against their advertised plans. The headline: fibre providers consistently deliver near 100%; major cable players hover in the 75-80% range; 5G fixed-wireless is the wildcard with results that swing 50-80% depending on tower load.
The leaderboard
| ISP | Type | Avg % of advertised speed |
|---|---|---|
| Verizon Fios | Fibre | ~95% |
| AT&T Fiber | Fibre | ~92% |
| BT Full Fibre (UK) | Fibre | ~90% |
| JioFiber (India) | Fibre | ~88% |
| Spectrum | Cable | ~80% |
| Xfinity | Cable | ~78% |
| Cox | Cable | ~76% |
| T-Mobile Home Internet | 5G FWA | ~70% |
Reading the table
Fibre wins. Symmetrical fibre lines from Verizon, AT&T, BT and JioFiber consistently hit within 5-10% of the headline number, and most of that gap is your own Wi-Fi.
Cable plans are the “up to” category — they advertise peak burst speed, not sustained speed, and DOCSIS oversubscription means peak hours pull users into the 60-70% range.
5G fixed-wireless is the most variable category. We see users at 200 Mbps off-peak collapse to 30 Mbps in the evening if their tower is loaded.
What this means for you
- If you're on cable and below ~75% of plan, that's normal — not great, but normal. Worth a complaint call only if you're below 60% repeatedly at off-peak hours.
- If you're on fibre and below 85% of plan, you almost certainly have a Wi-Fi or modem problem — not an ISP problem. Test wired before calling.
- If you're on 5G FWA and your speed is wildly inconsistent, that's the technology, not your hardware.
Test your own line
Run NetStartr free, pick your plan in the “Am I getting what I pay for?” slider, and read off your percentage. Three timestamped tests at peak and off-peak give you the evidence base for any complaint call. Per-ISP guides are linked from /isp.
Methodology: NetStartr aggregates anonymous, opt-in delivery percentages reported by users's “Am I getting what I pay for?” selections, weighted by plan size. Numbers are illustrative ranges, not single-point measurements.