From the blog "The House at the Bottom of the Garden"

I just wanted to include a brief post explaining from a self-builder perspective why we have decided not to use an Unvented Cylinder (UVC), Thermal Store (TS) or combi-boiler for our domestic hot water (DHW) in our new build.  Instead we are using 2 × SunAmp PV heat batteries heated by E7 tariff.  So why? We decided that we don't need gas to be installed avoiding the Gas connection charges, per day supply charge and the maintenance costs on gas appliances.  Big saving here.