Gas Heat Only Boilers

Gas heat only boilers, also sometimes known as open vent boilers, provide heat to radiators and a hot water cylinder. Hot water is heated over a period of time and then stored in a hot water cylinder for use when needed, unlike a combi boiler which heats water instantaneously. As a result heat only boilers generally require less power output than a combi; a typical heat only boiler will be 15-20kW output rather than a minimum of 24kW output for a combi. Heat only boilers are also generally simpler and lower priced than system boilers. A system boiler has additional components built into the unit whereas a heat only boiler relies on external components such as a pump to circulate water round the system.

The choice between an heat only boiler or a system boiler is often driven by ease of installation. In an existing installation where the existing external components, such as the Grundfos pump shown in the photo, do not require replacement then a heat only boiler is a lower cost choice. System boilers have not been around so long so most existing installations will be using a heat only boiler. Where a totally new installation is being done then a system boiler may make more sense as the installer does not have to buy or install additional components.

Below we list the popular heat only boiler options by power output in kW and then brand. Note that the prices are for the boiler only and do not include the flue. They are also typical prices and do not reflect any price promotions with a specific plumbers merchant or retailer. On occasions, manufacturers offer promotional packages which include the flue.

See also prices for: System Boilers and Combi Boilers.

If you want an indication of what you may pay for a boiler replacement including installation then use our replacement boiler cost online calculator. You can then compare any quotations from installers with this guideline estimate.

Power Output	Product	Typical price inc VAT	Warranty Period Years *	Technical Details
9kW	Worcester Bosch Greenstar 9Ri	£887.29	5	View
12kW	Baxi 200 Heat 12	£766.78	3	View
12kW	Baxi 400 Heat 12	£785.56	3	View
12kW	Glow-worm Energy 12kW regular	£786.99	7	View
12kW	Ideal Logic Heat H12	£729.21	2	View
12kW	Ideal Logic Max Heat H12	£874.99	10	View
12kW	Ideal Logic+ Plus Heat H12	£768.35	7	View
12kW	Potterton Titanium 12 heat	£734.50	7	View
12kW	Vaillant ecoFIT pure 412 regular	£767.60	2	View
12kW	Vaillant ecoTEC plus 412 regular boiler	£822.91	5	View
12kW	Worcester Bosch Greenstar 12Ri	£851.24	5	View
15kW	Baxi 200 Heat 15	£801.48	3	View
15kW	Baxi 400 Heat 15	£810.13	5	View
15kW	Glow-worm Energy 15kW regular	£806.78	7	View
15kW	Ideal Logic+ Plus Heat H15	£878.73	7	View
15kW	Ideal Logic Heat H15	£766.75	2	View
15kW	Ideal Mexico HE 15	£1,130.11	2	View
15kW	Ideal Logic Max Heat H15	£961.25	10	View
15kW	Potterton Titanium 15 heat	£773.50	7	View
15kW	Vaillant ecoTEC plus 415 regular boiler	£882.29	5	View
15kW	Vaillant ecoFIT pure 415 regular	£802.06	2	View
15kW	Worcester Bosch Greenstar 15Ri	£857.23	5	View
18kW	Baxi 400 Heat 18	£844.41	5	View
18kW	Baxi 200 Heat 18	£786.25	3	View
18kW	Glow-worm Energy 18kW regular	£847.99	7	View
18kW	Ideal Mexico HE 18	£1,221.85	2	View
18kW	Ideal Logic Heat H18	£799.48	2	View
18kW	Ideal Logic+ Plus Heat H18	£835.04	7	View
18kW	Ideal Logic Max Heat H18	£951.04	10	View
18kW	Potterton Titanium 18 heat	£812.50	7	View
18kW	Vaillant ecoTEC plus 418 regular boiler	£993.73	5	View
18kW	Vaillant ecoFIT pure 418 regular	£876.04	2	View
18kW	Worcester Bosch Greenstar 18Ri	£917.75	5	View
21kW	Worcester Bosch Greenstar 21Ri	£1,028.88	5	View
24kW	Baxi 200 Heat 24	£875.71	3	View
24kW	Baxi 400 Heat 24	£899.49	5	View
24kW	Ideal Logic Heat H24	£837.56	2	View
24kW	Ideal Mexico HE 24	£1,688.56	2	View
24kW	Ideal Logic Max Heat H24	£985.46	10	View
24kW	Ideal Logic+ Plus Heat H24	£875.46	7	View
24kW	Potterton Titanium 24 heat	£851.50	7	View
24kW	Vaillant ecoTEC plus 424 regular boiler	£1,055.19	5	View
24kW	Worcester Bosch Greenstar 24Ri	£972.35	5	View
25kW	Glow-worm Ultimate 3 25kW regular	£802.94	5	View
25kW	Glow-worm Energy 25kW regular	£883.99	7	View
25kW	Vaillant ecoFIT pure 425 regular	£952.06	2	View
27kW	Worcester Bosch Greenstar 27Ri	£1,090.69	5	View
30kW	Baxi 200 Heat 30	£893.94	3	View
30kW	Baxi 400 Heat 30	£976.50	5	View
30kW	Glow-worm Energy 30kW regular	£927.93	7	View
30kW	Ideal Mexico HE 30	£2,074.00	2	View
30kW	Ideal Logic Heat H30	£953.23	2	View
30kW	Ideal Logic Max Heat H30	£1,156.25	10	View
30kW	Ideal Logic+ Plus Heat H30	£993.30	7	View
30kW	Vaillant ecoFIT pure 430 regular	£1,012.48	2	View
30kW	Vaillant ecoTEC plus 430 regular boiler	£1,109.35	5	View
30kW	Worcester Bosch Greenstar FS 30CDi Regular	£1,732.88	5	View
30kW	Worcester Bosch Greenstar 30Ri	£1,136.60	5	View
30kW	Worcester Bosch Greenstar 30CDi Classic Regular	£1,216.28	5	View
32kW	Potterton Titanium 32 heat	£877.50	7	View
35kW	Vaillant ecoFIT pure 435 regular	£1,495.81	2	View
35kW	Vaillant ecoTEC plus 435 regular boiler	£1,597.91	5	View
36kW	Ideal Mexico HE 36	£2,857.16	2	View
40kW	Worcester Bosch Greenstar 40CDi Classic Regular	£1,690.98	5	View
42kW	Worcester Bosch Greenstar FS 42CDi Regular	£2,363.59	5	View