The majority of homeowners will switch off their heating in the summer, assuming they live in a relatively warm climate. In the summer months, many people won't want their radiators active at any point and will probably change their settings to keep their heating inactive. Even so, your boiler will continue to consume some amount of fuel as long as it is switched on, regardless of whether or not your central heating is operating. Turning off your boiler and acquiring your hot water in other ways will obviously reduce your energy bills but is it advisable to completely shut down your boiler for an extended period?
In many cases, older boilers (usually more than fifteen years old) will be the ones that you want to switch off, particularly those that feature a constantly burning pilot light. The pilot light will consume fuel so there isn't much point in leaving it on while your radiators are inactive for months. Modern combi boilers often feature summer and winter modes, with the summer mode reducing fuel expenditure by only heating your water for a couple of times per day. If you're relying on your boiler to provide warm water for baths, showers and washing your dishes, it may be necessary to leave your boiler active, if only to ensure your hot water tank is filled a couple of times per day. Electric showers have the benefit of not needing a hot water supply; they heat water almost instantaneously using a heated element in the shower unit itself, meaning you don't have to worry about impacting their effectiveness if you switch off your boiler. Washing machines and dishwashers can be another concern; older units may require a hot water supply but many should still be able to heat water internally. The majority of modern washing machines and dishwashers only require a cold water supply and won't need to be taken into consideration when you decide whether or not to turn off your boiler.
If you do decide that you'll be able to turn off your boiler for the summer, it's still a good idea to occasionally run your hot water and central heating systems. Even in a modern, reliable hot water system, there are moving parts in the pump and diverter valve that can seize up and cause issues when you want to reactivate it in subsequent months. This doesn't need to happen every day; running your boiler and turning on your hot water for a while every few weeks should be sufficient to keep it in working order. Modern boilers usually feature a standby mode, which consumes considerably less fuel than older boilers when not in use. Even so, it may still be worth turning off your boiler if your hot water cylinder lacks adequate insulation, forcing your boiler to do more work.
Whether you switch your boiler off or not, it's important to have it serviced annually, ideally during the summer. Be careful not to wait until your heating is required to have it serviced; most heating engineers will be extremely busy during the autumn and winter months and winter is the worst possible time to experience a boiler failure. Preventing boiler issues is always better than having the unit repaired afterwards, especially when it's freezing outside. If you're a landlord, annual services are compulsory and you'll need a gas safety certificate to show that you've had your heating serviced. For homeowners, this isn't mandatory but it's still well worth it; servicing costs less than repairing. Running your boiler every few weeks throughout the summer and ensuring it's serviced at some point during this period should ensure that your boiler works properly whenever you need it.