How Much Does It Cost to Run a Cable or Fiber Modem in the UK? (2026)

A modem runs all day at 5 to 15 watts. Combined with a separate router the pair uses around 15 to 25 watts continuously, roughly 150 to 200 kWh a year.

A typical cable or fiber modem (8 W) costs £0.002 per hour, or about £1.52 per month at 24 hours a day in the UK. Cheap to run

Electricity price region

Hours used per day

Wattage	Per hour	Per day	Per month	Per year
Low 5 W	£0.001	£0.032	£0.95	£11.53
Typical 8 W	£0.002	£0.051	£1.52	£18.45
High 15 W	£0.004	£0.095	£2.84	£34.58

Formula: watts ÷ 1000 × hours × price per kWh. Typical use is 24 h/day ≈ 70 kWh per year.

One day of a cable or fiber modem (0.19 kWh) is the same electricity as

3.8hours of a fridge
4.3hours of a laptop
19hours of Wi-Fi
21hours of an LED bulb

Electricity per year at typical use, on a log scale: #26 of 95 appliances, from least to most.

In the UK, with electricity at 26.3p per kWh (source: Ofgem price cap 1 Oct–31 Dec 2026, 2026-10), a typical cable or fiber modem costs £0.002 per hour and about £18.45 per year at 24 hours a day. Each £1.00 of electricity buys roughly 474.9 hours of use.

How to lower the cost of running a cable or fiber modem

Replace a separate modem and router with a combined gateway to halve the draw.
Do not turn it off at night. Reconnection delays are rarely worth the small saving.
Retire old network gear. Older units often use double the power of current ones.

Frequently asked questions

How much electricity does a modem use per month?

Around 6 kWh a month at 8 watts continuous.

Is it worth turning off the modem at night?

It saves about 2 to 3 kWh a month. Most people find it not worth the hassle.

Do fiber ONTs use less power than cable modems?

Usually a little less, typically 5 to 8 watts.

Cost by region

US states

Canadian provinces

Related appliances

Use the generic electricity cost calculator · Which uses more? Take the quiz