Natural gas is the cleanest of the various fossil fuels. Gas central heating systems however, do produce damaging greenhouse gas and with climate targets increasing, gas will become obsolete in the coming years.
Indeed, official Government directive is that there will be no new gas installations allowed in new build houses beyond 2025. Whilst gas is cheaper than electricity to run on a daily basis, the true costs to consider are initial installation, plus annual servicing, maintenance and running expenses, along with the length of its useful life. A central heating system is always much more invasive to install too, requiring floorboards to be taken up and unsightly pipes to be run up walls and along skirting boards. Gas heating wastes energy through the pipework. As the heated water snakes its way through the pipe system, heat will radiate from the pipes.
You will also generally have to activate the whole system, even if you just want a single radiator on. This is neither convenient, cost or energy efficient.