Gauges work on pressure in the bottle so a gauge will read OK when in fact there is very little gas left in the bottle. [The gas in a bottle is in liquid form hence L liquid P petroleum G gas ] it turns to gas as it escapes the regulator so is safe to burn.You can weigh bottles to find out how much is left in the bottle but this is a bit hit and miss, what modt of us do is have a spare bottle connected and the valve closed , when the bottle in use runs out just open the valve on the full one and off you go, you then know that you need to get a replacement for the empty one, there are all sorts of automatic change over valves you can fit to save you turning on the full bottle but you may not then know that this has happened and end up with two empty bottles, keep it simple I say. If you are on hook up it makes sense to run your fridge and any thing else for that matter on mains as you will pay the same amount of money for electric irrespective of how much you use,unless the site meters the lecky , some do most don't, be aware that a hook up feed can vary from 4 amps to 16 amps so according to what you are on you must switch things off if you turn the kettle on or use a fan heater, if you overload the hook up a trip will shut the feed off, this is no big deal as usually you can reset the trip and off you go again, however on some sites this will involve the Warden coming out and unlocking a box containing the trips and they tend to get a bit shirty if you keep doing it LOL.:danger::danger: When hooking up you MUST connect the end to your van first ,then then the plug to the hook up Power point, this is for safety ,never leave a live cable on the grass as this is dangerous, I mean if it is connected to the Hook up bollard and not to your van.:danger::danger: