Business broadband and leased lines look similar on a price sheet and behave very differently under load. In this post, we’ll compare leased line vs business broadband to help you understand the differences. The short version is this.

Business broadband is a shared connection with best-effort speeds. A leased line is a dedicated connection with guaranteed speeds and a real SLA. Which one fits your business depends on how many people rely on it, how much an hour of downtime would cost you, and whether your day starts with video calls or ends with a cloud backup.

This guide is for UK SMEs weighing up leased line vs business broadband in 2026. It covers a quick side-by-side, the differences you feel in daily use, the cost bands to expect, and a four-question test that gets most businesses to the right answer in under a minute.

The short answer: how they compare

Both connect your office to the internet. What changes is who else is on the connection, what the provider guarantees, and what happens when it breaks.

Feature	Business broadband	Leased line
Typical monthly cost	£30 to £80	£150 to £800+
Download speed	40 Mbps to 1 Gbps (best-effort)	100 Mbps to 10 Gbps (guaranteed)
Upload speed	10 to 100 Mbps (asymmetric)	Matches download (symmetric)
Contention	Shared with other users	Dedicated to your business
Uptime guarantee	Best-effort only	99.9% or higher with service credits
Fix-time target	Best-effort	4 to 24 hours, contractual
Install lead time	1 to 4 weeks	30 to 90 days
Typical fit	1 to 15 people, non-critical use	Mission-critical, VoIP-heavy, cloud-first, larger teams

What business broadband gives you

Business broadband runs over the same FTTC or FTTP fibre that consumer broadband uses. What you get on top is business-grade support, a static IP, and often a small SLA around fix times. The connection itself is shared. Openreach and altnet providers typically run their networks with a contention ratio of around 20:1, which means twenty premises share the same core capacity.

That is fine for a small office where five to ten people are on email, Teams calls and the occasional file transfer. It gets uncomfortable at around fifteen users with a busy VoIP setup and a nightly cloud backup pushing 100 GB. Upload is where broadband hurts first. Most business FTTP plans still cap upload at 100 Mbps or less, and video conferencing, cloud backup and remote desktop all live on the upload side of the connection.

Gigabit-capable business broadband is now available at 89% of UK premises according to Ofcom’s Spring 2026 Connected Nations update, so speed on paper is rarely the blocker. Consistency under load is.

What a leased line changes

A leased line is a private circuit between your office and the provider’s core network. Nobody else uses it. The speed you pay for is the speed you get, in both directions, at any hour.

The SLA is contractual. 99.9% uptime means no more than nine hours of downtime a year, with service credits paid when it slips. The fix-time target is usually 4 to 24 hours, not “when we can get to it”.

The trade-off is time and money. A leased line install involves a site survey, sometimes Excess Construction Charges if new fibre has to be pulled in, and a lead time of 30 to 90 days from order. Cost sits in the £150 to £800/month band for typical UK SME speeds, with the higher end reflecting 1 Gbps symmetric on a longer contract.

Cost: the honest picture

Business broadband is around £30 to £80 a month with minimal install cost, usually on a 12 to 24-month contract. A leased line is £150 to £800+ a month on a three to five-year contract.

The line item that catches businesses out is Excess Construction Charges (ECC). If a leased line needs new fibre to reach your building, the provider passes on the civils cost. On a straightforward city-centre site this is usually zero. On an out-of-town business park or a listed building, ECC can run from a few thousand pounds into six figures.

Openreach raised its ECC exemption to £3,680 in 2026, which absorbs the cost on shorter builds, but larger jobs are still passed through. Always ask for the ECC number after the survey, before you sign.

Reliability: what an SLA is worth

The word “reliability” gets used loosely. A concrete way to compare:

• Business broadband typically achieves 99.5 to 99.7% uptime in practice. That sounds fine until you convert it. 99.5% is around 44 hours of downtime a year. There is no financial recourse when it goes down.
• Leased line SLAs guarantee 99.9 to 99.99% uptime with service credits when missed. 99.99% is around 52 minutes a year. If the line is down beyond the fix-time target, you get billed less for the month.

The right question is what an hour of downtime costs your business. If a full outage means twenty people sitting on their hands, that number is often larger than a year of leased-line premium in one afternoon.

Speed you get in practice: why upload matters

Advertised broadband speeds are a best-case. Real-world speeds under Ofcom’s Code of Practice run around 60 to 90% of the advertised figure at peak times, and asymmetric upload becomes the visible bottleneck for anyone on video calls, remote desktop or cloud backup.

Leased-line speeds are quoted and delivered. If you buy 200 Mbps symmetric, you get 200 Mbps up and 200 Mbps down at 9am, at 4pm, and at midnight.

For businesses running cloud-hosted phone systems, Microsoft 365 workloads or large regular backups, that predictability tends to be worth more than the raw speed number. A rough rule of thumb for sizing: 5 Mbps symmetric per user for a mixed workload, doubling for VoIP-heavy or cloud-desktop teams. A 25-person office typically lands at 100 to 200 Mbps symmetric.

How to choose: a four-question test

Most businesses can get to the right answer with four questions.

1. Do more than ten people need the connection at once during working hours?
2. Do you make more than five concurrent voice or video calls at peak?
3. Would four hours of internet downtime cost your business more than £500?
4. Are you cloud-first for your core apps (Microsoft 365, hosted phone system, hosted accounting)?

Two or more yes answers: a leased line is usually worth it, and often pays for itself in avoided downtime and productivity within the first year.

One or no yes answers: business broadband is likely enough, particularly if you add a 4G or 5G backup line for resilience.

Common mistakes when comparing options

• Reading the advertised broadband speed as the real speed. Business broadband is best-effort and asymmetric. Compare like for like.
• Ignoring the upload figure. For most modern businesses, upload is the bottleneck, not download.
• Signing a five-year leased-line contract at undersized bandwidth. Speed upgrades mid-contract are possible but usually reset the term. Buy for where the business will be in two years.
• Not budgeting for ECC. Get the survey and the ECC quote before signing anything.
• Treating “SLA” as a single word. Read the actual uptime figure, the fix-time target and the service credit table.
• Skipping the resilience question. Even a leased line goes down occasionally. A well-designed SD-WAN and backup internet setup turns that into a seamless failover.

A second look at your connectivity setup

If you would like a second pair of eyes on your current setup before you sign the next contract, get in touch and we will walk through what your existing line is delivering, what your team’s workload really needs, and whether an upgrade is worth the money in 2026.