Free tool

Garden Room Running-Cost Calculator

Enter your own dimensions, insulation level and electricity tariff. We do the sum and show every step — heat loss, then kWh, then cost. It's your numbers, not ours.

Your garden room

Floor area (m²)

Insulation level

Basic — U-value ≈ 0.35 W/m²KMeets the minimum standard for an insulated garden room — expect noticeable heat loss through the walls and roof on cold days.Standard — U-value ≈ 0.25 W/m²KBroadly in line with current Building Regulations for a home extension — a well-built, comfortably insulated room.High — U-value ≈ 0.18 W/m²KHeavily insulated, closer to a low-energy specification — minimal heat loss even through winter.

Hours/day heated

Months/year in use

Your electricity tariff (p/kWh)

Not pre-filled — use the unit rate from your own electricity bill or tariff.

Fill in your garden room’s details and your own tariff to see the running-cost estimate and the working behind it.

More free tools

Access & Delivery Checker

Find out which build methods your garden access rules in or out.

Quote-Comparison Checklist

A printable list of everything to ask before comparing quotes.

See all free tools