I have an L5 but went for this during the summer heat. Costs nothing to run off the waste heat from the car rad system. I like to try things before reccomending them so that will be the spring I got on very well last winter with just bringing in containers and storing overnight next to rads, temp about 25 degrees. but over the summer I had an itch to try storage water on a bigger scale so found these and fitted them, bleeding the car rad system was a slightly difficult, But I now have mulled wine on tap for Christmas. http://www.ebay.co.uk/itm/NARROWBOAT-AND-MARINE-calorifier-/180875242570?pt=UK_CarsParts_Vehicles_BoatEquipment_Accessories_SM&hash=item2a1d012c4a The thing is now that I have done it, I have realised just how much heat a car engine wastes, we are messing about with Windmills but have millions of vehicles on the raod, if only someone could capture that waste we could almost run a couple of power stations with it, its enormous. Current tank temp at 6.15pm Sat is 28 C check back tomoz and I will post the morning temp. The immersion raises the water temp by 1 degree in 1 min. 1"BSP fittings for the tank or plastic equiv. a pair of taps for the car rad in and out - so that the whole thing can be taken out. Welded bracket anchored to the seat belt fixings. Enough space above it to be able to put water in the top.I pump from the IBC. Cut the car hose and insert "T" s to circulate round the cylinder then bleed. I did think about putting a thermo tap on the in side but it was an extra £30 so make do with turning the tap on for 20 min or so when the engine is hot. Water stays warm all day as does the car.100 degress F is the hotest I have used temp taken at the top with a fish tank thermometer, the tap at the bottom (Supply)of the cylinder is far cooler. When I get home I top up the cylinder and theres usually enough warm water to stay warm till the next morning. The downside for the majority that are not water efficient is, that it holds approz 50-60 litres so not for the guys that use 2L per minute. I use approx 40 litres per day so its been designed for my useage. But you could buy larger cylinders for more money and running costs etc.