Yes! It is perfectly acceptable to keep the records of your gas inspection electronically – and many landlords find it far more convenient.
As long as you can produce a hard copy when needed (such as when new tenants are moving in), you keep it safe (i.e. you don’t delete if from your electronic records) and it uniquely identifies the engineer (e.g. with a signature), having only an electronic copy is absolutely fine. If sharing an electronic copy with your tenants, be sure they first have the means to access it.