I have a stone house in Covilhã that gets freezing in winter. The radiators I have are really old and they consume a ton of energy. I'd like to know if it's worth switching to a gas boiler or if there are other more economical solutions.
A gas boiler is a solution, but it's not the only one and it's not always the cheapest depending on the situation. In my case, I had a house with insulation problems and old cast iron radiators - the heating bill was ridiculous. Before throwing money at a new boiler, I did some simple tests: sealed the windows properly with weatherstripping, stuffed foam in the door gaps, and that already made a noticeable difference without spending anything significant.
The thing is, a modern gas boiler definitely uses less than those old radiators, but if the house has air leaks, you're always going to be heating the street. It really does pay off to do the sealing first - it's a low investment and quick to do. Then, if you still think you need it, that's when you evaluate a gas boiler or even a heat pump if you have the space. But in Covilhã the winter is harsh, so maybe a well-insulated boiler is the most practical solution in the medium term.
Another thing: the localized heaters they mention there can help you save on central heating, but if you use them every day they also consume energy - it's more for supplementing specific rooms than for replacing the whole system.
Start by sealing air leaks - windows, doors, crevices - because the best energy is the energy you don't spend. If the house is stone and really old, a gas boiler can be worth it, yeah, but first get an energy audit done (your local council sometimes offers it for free) to figure out exactly where the heat's going. In the meantime, solar thermal panels or a heat pump are pricier upfront but they pay off in durability and savings down the line - but if you're looking at the short term and cash is tight, swapping out the old radiators for efficient modern ones makes a pretty big difference without breaking the bank.
If your radiators are really old, a modern gas boiler makes a lot of sense - it uses way less fuel than those old things. But before you invest in that, it's worth testing portable heaters in the rooms you use most (living room, bedroom), because sometimes it pays off to just heat where you need it instead of pumping energy through the whole house. In stone houses insulation is poor, so even small things make a difference - while you're at it, close off the rooms you're not using and leave the radiators on only where you actually are.
Old radiators do consume a lot, but before replacing the whole boiler I'd test some oil heaters or even infrared panels in the rooms you use most - it's way cheaper and solves the problem without any work. A stone house in Covilhã is genuinely freezing, so the window and door insulation the others mentioned is essential, but honestly with just that you'll already notice a difference without spending a fortune. If after that you still think you need more heat, then it's worth considering a gas boiler, because the investment only pays off if you've already done the basics.
I had a similar situation and what really made a difference was combining several things instead of betting everything on a new boiler - I put up thicker curtains, sealed the window gaps with foam tape, and then in the rooms where I spent the most time I installed these tiny electric radiators that I'd turn on when needed! That cost me a fraction of the price of a gas boiler and already in the first winter I felt a brutal difference in my electricity bills. A stone house is really tricky because humidity also works against you big time, so before getting into major renovations I'd try these cheap tricks first, because a lot of people jump straight to a boiler without realizing that sometimes it's just a matter of keeping the heat from escaping through the window!
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