Hi JoshuaChristy,

I would suggest, if you have not all-ready, to look at any off peak tariffs that may be available in your area so you can help even out the supply companies load curve and save money!
If you have more than one bathroom you could also fit an electric shower so that if your tank is up to temperature by the morning it would effectively be off load and so you could have an 11Kw shower installed for any daytime use-age.

https://www.quora.com/How-much-would-a-5-minute-shower-cost-in-terms-of-water-and-electricity-in-the-UK

I hope this helps.
Regards

Jim

You could upgrade to a bigger cylinder if you have room if not an electric combi can be installed but you would have to contact your energy supplier as your existing main fuse would have to be upgraded depending on kilowatts your new combi will require

I would look into costs of combi boiler against electric power shower. Power shower will heat instantly

As an addition to the above replies, which element is heating-the one mid way up the side of the cylinder or the lower one? Try connecting the lower one up if it isnt already-45 litres of hot water per person seems excessive-normally ⅔ hot water to ⅓ cold mixes water to shower temperature which would mean that youre using over 60 litres of water per shower otherwise! Bet thats the reason and its a cheap fix!

The Combi boiler is worth investigating with a competent plumber and the answer fit an electric shower in one of the bathrooms/en-suite. But thought I would mention a couple of things that you might have tried or not first.

1. Has the hot water timer been set to be on early enough before use to charge a full tank of hot water from previous day ?

2. Is the tank thermostat turned up enough. As the hotter the hot water the less you will use when mixing with the cold water at shower.