If you are referring to a gas, oil or solid fuel boiler then it would likely work OK however if the boiler takes its power (rather than control) from the socket then it could be overloaded.
Most electrical items will have a plate somewhere giving the power they use problem for house holder is this is normally in watts not amps.
So 230 watts = 1 amp so 13 amp = 2990 watts normally considered as 3kW if you add all the watts and it is under 3000 or 3Kw then it will work OK.
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