Should I convert my boiler from gas to electric?
My house’s heating system is gas-fired hot water. It’s a fairly efficient system, but I’ve been thinking of swapping the boiler out and installing an electric boiler.
Here’s my thinking, Electric boilers are more efficient, of course. But they give me more flexibility in the actual “power source.” With natural gas, the prices fluctuate during oil crises, and there’s only one source for gas in my city.
But with electricity, I can get power from more than one power company. If I install photovoltaics, their power could offset my heating bills. And if the country moves to a more sustainable power grid, I’d be better placed to benefit.
This looks like a worthwhile investment to me, but I’d like to learn more– sources of information on relative efficiencies, what are the high quality units, what else is required (should I upgrade my electrical service to handle the higher juice load?) and much more.
Any advice? Thanks.
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Replies
Brian,
It's hard to imagine circumstances where your suggestion makes sense. In most cases, the money you would spend to buy an electric boiler would be better spent elsewhere — for example, on air tightening or added insulation.
1. Electricity is a very expensive fuel compared to natural gas.
2. Homeowners with photovoltaic systems do not usually use electricity for heat, unless the envelope of their home has been improved to an unusually high standard.
3. On average, 50% of the electricity generated in the U.S. comes from a coal burning power plant, with disastrous effects on the planet.
4. It makes more sense to burn a fossil fuel directly to produce heat than to inefficiently burn the fuel to generate electricity, and then use the electricity to produce heat.
5. Even if you want to use electricity to produce space heat, it makes more sense to use a ground-source heat pump than an electric boiler.
I'll agree with Martin on this. But let's dispell the myth that using electicity for space or water heating is "efficient". It's "efficient" only in the sense that what enters your house is more completely converted to heat, but from power plant through transmission and distribution lines to your house, electricity is generally 35% efficient in thermal conversion of fuel.
The best solution is going to depend on your climate, particularly how much sun you see and how much heating you have to do over the course of the year.
Heating with PV-produced electricity is EXTREMELY expensive. Ground-source heatpumps are costly, but the 3-6 COP (allowing you to use 3-6x less PV) probably makes it a cheaper solution. Still expensive, though.
Electricity prices in some places are less volatile than gas in the short term, due to the way the utilities are regulated. Long term, though, I wouldn't bet one way or the other.
Realize that grid-tied PV (i.e. no batteries) doesn't make you independent of the grid -- if the grid goes down, so does your system.
If you want the maximally robust and flexible solution, I would look into solar hot water panels, using a superinsulated electric heater (eg. http://www.marathonheaters.com/) as a storage tank. In that context, the electric heat is a backup, and the high insulation level really pays off. The effectiveness of the solar hot water panels for winter heating will depend a great deal on your local winter climate. Under any circumstances, a sufficiently large system for winter use will massively overproduce hot water during the summer.