Do you need a leased line? A practical guide

What a leased line actually is

A leased line is a dedicated point-to-point Ethernet connection from your building to the supplier's core network. Three things make it different from business broadband:

• Uncontended. The bandwidth is yours, full-time. You are not sharing the line with neighbours, so peak-time slowdowns do not happen.
• Symmetric. Upload speed equals download speed. Standard fibre broadband is heavily asymmetric — fine for general browsing, less fine if you run a server or push large uploads.
• Real SLAs. Guaranteed uptime (typically 99.95%) with credit-back if the supplier misses it. Target fix times measured in hours, not days.

Leased line vs business broadband — the honest comparison

Business broadband (FTTP) at 1 Gbps costs roughly £40–80 per month + VAT in most parts of Wales. A 1 Gbps leased line costs £400–800 per month + VAT depending on location and supplier. That is roughly a 10× price difference.

What you get for the extra spend: guaranteed bandwidth (not "up to"), symmetric upload, hard SLAs, dedicated support, and a static IP block. What you do not get: faster headline speed than a comparable business FTTP plan.

When you genuinely need a leased line

• You run services hosted on-site. If customers or staff are connecting to a server in your building, you need upload bandwidth that does not collapse during the working day.
• You have a multi-site VPN backbone. Connecting offices together over a private circuit is the bread-and-butter use case for leased lines.
• Downtime measurably costs you. If an outage costs you more in lost revenue per hour than the SLA-backed premium costs per month, the maths is straightforward.
• You are hitting contention on broadband. If your team complains about evening slowdowns or peak-time call quality drops, you are sharing capacity with neighbours. A leased line solves that.
• Regulated workloads. Some industries (healthcare, payment processing) require uncontended, audited connectivity.

When you do NOT need a leased line

• Small office, cloud-only services, no on-site hosting — business broadband with optional 4G failover is almost always sufficient.
• You think you need one because the salesperson said so. Salespeople are paid more on leased lines. Get a second opinion.
• You can solve the problem with optional 4G failover instead. A backup SIM costs £20/mo. Leased line costs £500/mo. Different problems, different answers.

SLAs and what they really mean

Standard leased-line SLAs run something like: 99.95% uptime, 4-hour or 6-hour target fix time, proactive monitoring, credit-back if the supplier misses the targets. Look at the SLA carefully:

• Is the uptime measured per month or per year? Per month is stricter.
• Is the fix time a "target" or a "guarantee"? Targets are softer — credit only kicks in past the threshold.
• What's the maximum credit? Some SLAs cap credit at one month's rental, which can be lower than your actual downtime cost.

Bandwidth choices

Leased lines are sold as "bearer × access":

• Bearer: the physical maximum the circuit can carry. Usually 100 Mbps, 1 Gbps or 10 Gbps.
• Access: what you actually pay for. Can be less than the bearer — e.g. 1 Gbps bearer with 200 Mbps access. Lets you upgrade later without re-installing the physical line.

For most SMEs a 1 Gbps bearer with 200–500 Mbps access is the sensible starting point. Bigger sites go higher.

Install timeline

Lead time for a new leased line is typically 60–90 working days. Most of that is the physical build work — survey, planning permission for any new dig, the actual excavation and cabling, plus equipment install at both ends. There is not much you can do to speed it up. Plan accordingly.

If the building already has fibre to the door, lead times drop substantially.

Cost reality

Headline pricing for leased lines varies massively by location. A 1 Gbps line into a Cardiff office park is much cheaper than into a rural Welsh village. Distance from the nearest fibre node drives the cost. Get a site-specific quote — generic "leased lines from £X" pricing on supplier websites is rarely what you will end up paying.

Alternatives if a leased line is overkill

• Business broadband with 4G failover. Two lines, two carriers, automatic failover. Roughly £80/mo all-in. Most rural SMEs do fine on this.
• Dual-supplier broadband. Two independent fibre lines from different suppliers, bonded or in failover. Works where genuine resilience matters but a leased line is overkill.
• Starlink as backup. Independent of the ground network entirely. Useful for sites where local fibre is fragile or single-route.

What we do at Cader Networks

We design and install leased lines for businesses across Wales — survey, scope, install, monitoring and ongoing support. See our business leased lines page for the install detail and a sample of bandwidth/SLA options. Send us your site address and a sketch of what you need and we will quote against it.