Patio Heater Running Cost Calculator

Estimate the cost of running an electric, mains gas or LPG patio heater per hour, per evening and across a season.

Heater And Tariff Inputs

Heater fuel Pick the energy source you actually pay for. Heater rating kWUse the input rating from the label or manual. Electricity or gas unit rate p/kWhEnter your supplier tariff. Ignore this for LPG cylinder mode. Heaters running together unitsUse more than one for pub gardens or larger patios. Hours per session hoursCount the time the heater is actually on. Sessions per week nightsSeasonal habits matter more than one evening. Weeks in season weeksEnter the period you expect to heat the patio. Heat setting used %For heaters that run on half power or cycling settings. LPG cylinder size kgOnly used for propane cylinder mode. Cylinder refill price GBPUse your local refill price, not the deposit. LPG energy factor kWh/kgEditable propane planning factor. Carbon factor kg CO2/kWhOptional estimate. Use zero to hide carbon weight.

Running Cost Result

GBP 0.50 per hour

Estimated cost for the selected fuel and setting.

Enter your own tariff or refill price for a fair estimate.

What The Running Cost Shows

This estimator turns a patio heater rating into a cost per hour, cost per session and seasonal cost. It is built for electric infrared heaters, mains gas heaters and LPG propane cylinder heaters. The key number is not only the heater size. The real bill depends on how long the heater runs, how many units are on together, whether it is run at full power, and whether the garden is used for a few evenings or every week for months.

For electric and mains gas heaters, the calculator uses the tariff rate you enter in pence per kWh. For LPG cylinders, it estimates an effective pence per kWh from the refill price, cylinder size and kWh per kg factor. That makes cylinder running cost easier to compare with mains fuel. Deposits, delivery charges and bottle swaps should be added into the cylinder price if they are part of the real cost for you.

The carbon estimate is optional. It uses the editable factor you enter rather than pretending one figure fits every tariff, supplier or fuel. Outdoor heating can use a lot of energy because heat escapes quickly in wind and open air. A lower setting, better shelter, shorter sessions, blankets and heating only the occupied area can reduce both cost and energy use.

Running Cost Formula

Effective heater power:

effective kW = heater rating x heat setting % x number of heaters

Electric or mains gas cost per hour:

cost per hour = effective kW x unit rate p/kWh / 100

LPG effective unit rate:

LPG p/kWh = cylinder price x 100 / (cylinder kg x kWh per kg)

Session and season cost:

session cost = cost per hour x hours per session

Seasonal energy:

season kWh = effective kW x hours per session x sessions per week x weeks

The calculation assumes the heater draws its rated input while on. Some heaters have thermostats, low-power modes or stepped settings, so the heat setting field helps adjust the estimate. It is still a planning number. A patio heater in a sheltered corner may keep people comfortable at a lower setting than a heater exposed to wind.

Worked Patio Heater Examples

Electric Table Area

A 2 kW electric heater at 25p per kWh costs about GBP 0.50 per hour. A three-hour evening costs about GBP 1.50. Twice a week for 16 weeks becomes about GBP 48 before any standing charge or supplier change.

LPG Cylinder Heater

A 13 kg propane cylinder priced at GBP 45 with 13.6 kWh per kg gives an effective fuel cost of about 25.5p per kWh. A 9 kW heater at full input costs about GBP 2.30 per hour, so long sessions can empty a bottle quickly.

Hospitality Patio

Two 2 kW electric heaters running four hours on Friday and Saturday use 32 kWh per week at full power. At 25p per kWh, that is GBP 8 per week. For a longer season, the result can justify timers, zoning or better shelter.

Cost Comparison Table

Heater Setup	Assumption	Cost Signal	Planning Note
1 kW electric	25p per kWh	GBP 0.25 per hour	Small seated area, low output.
2 kW electric	25p per kWh	GBP 0.50 per hour	Common domestic infrared heater.
3 kW electric	25p per kWh	GBP 0.75 per hour	Check plug, circuit and manual.
9 kW LPG heater	25.5p per kWh effective	GBP 2.30 per hour	Large output, bottle cost matters.
Two 2 kW heaters	25p per kWh	GBP 1.00 per hour	Better coverage but twice the energy.
2 kW at half power	50% setting	GBP 0.25 per hour	May suit sheltered evenings.

Safety And Placement Checks

Outdoor heaters still need careful placement. Keep clear space around the heater, follow the maker’s distances from awnings, furniture, fencing, parasols and plants, and do not use an outdoor heater inside a tent, shed, conservatory or enclosed room unless the manufacturer specifically allows that use. LPG heaters also need ventilation and correct cylinder handling.

Check the electrical route before running a heater outdoors. Use an outdoor-rated socket or suitable protected supply, keep leads away from water and trip routes, and do not overload an extension reel. For gas, check the hose, regulator, flame pattern and cylinder storage instructions. If a heater smells of gas, cuts out repeatedly or shows damage, stop and seek competent help.

Comfort can be improved without simply adding more heat. A windbreak, closer seating, rugs, seat cushions, warm drinks and timed heating often cut cost. Heat the people, not the whole garden.

FAQs

How much does a 2 kW patio heater cost per hour?

At 25p per kWh, a 2 kW electric patio heater costs about GBP 0.50 per hour at full power. Change the unit rate to match your tariff.

Is LPG cheaper than electric for a patio heater?

It depends on the refill price, cylinder size and heater rating. LPG heaters often have much higher output, so the hourly cost can be higher even if the effective pence per kWh looks similar.

Does the standing charge matter?

For a short session comparison, the unit rate is the main cost. Standing charges are paid anyway on many tariffs, but they still matter to total household energy bills.

Can I use a patio heater indoors?

Do not use an outdoor patio heater indoors unless the manufacturer explicitly says that model is suitable for that space. Gas heaters in enclosed spaces can create serious fire and carbon monoxide risks.

Why is the carbon factor editable?

Fuel and electricity carbon factors vary by source, reporting year and tariff. The calculator lets you enter the factor needed for your own estimate or set it to zero.

What is the easiest way to cut cost?

Run the heater for fewer hours, use a lower setting, heat a smaller seating area, shelter the patio from wind and avoid leaving the heater on when nobody is seated outside.

Sources

Ofgem. (n.d.). Energy price cap. Ofgem. https://www.ofgem.gov.uk/energy-price-cap
Department for Environment, Food and Rural Affairs. (2025). Greenhouse gas reporting: conversion factors. GOV.UK. https://www.gov.uk/government/collections/government-conversion-factors-for-company-reporting
Health and Safety Executive. (n.d.). Gas safety. HSE. https://www.hse.gov.uk/gas/