The hybrid-electric house will be the first way we in New England – Vermont in particular – begin our switch from imported oil to electrically delivered energy. IMHO plug-in hybrid cars and pure electrics will join the mix in the next couple of years, but practical electric vehicles for most uses aren't on the market yet. Everything we need for the hybrid house already exists and already makes sense – WITHOUT subsidy. Off-peak electric rates and later dynamic rates from the SmartGrid will make the economics of the hybrid house even better, but the economics are already favorable where capital is available. If you are concerned about CO2 emissions and you live in Vermont, the carbon footprint of your hybrid house will be much lower than it was when you were heating with oil or propane (as 72% of us are) since two-thirds of our electricity comes from carbon-free sources and the remaining third mostly from low-carbon natural gas.
Oh yeah, what's a hybrid-electric house? It's a house which is partially heated by electricity and partially by fossil fuel. You probably wouldn't build a new house with both oil and electrical heat; but it's a great way to retrofit an old house which has an existing furnace.
Ground source heat pumps (also known as geothermal) are expensive to install but by far the cheapest way to use electricity to heat a home in terms of operating expense. Electric storage heat is less costly to install and more expensive to operate than geothermal but considerably cheaper to operate than oil – so long as your utility supports time-of-day pricing. The cheapest form of electric heat to install but the most expensive to operate is electric resistance heating.
Geothermal heat is sometime referred to as being 350% efficient. What this really means is that you can get as much as 3.5x times as many BTUs out as the kilowatt-hours you expend. This isn't a violation of the laws of physics; what's really happening is that the electricity is being used to mine heat from ground water; the heat is already in the ground water – the sun put it there during the summer. Even at "300% efficiency" (my experience with geothermal), using electricity at $0.155/kwh (the Vermont average) to run my heat pump is equivalent to buying heating oil at $1.67/gallon.
A geothermal installation'll run from $10,000 to over $20,000 depending on what kind of heat you already have in the house and whether you have a suitable well. I saved money by slightly undersizing my installation knowing that the furnace'll be used on the coldest nights or if there's an electric failure so mine is a hybrid house. I'm also planning for the day when I can get cheap off-peak or even cheaper dynamic priced electricity. If peak electricity is expensive at a particular time, I (or preferably a cheap piece of electronics) will switch off the electricity for a little while and let the furnace run. I strongly suspect that, not too far in the future, utilities will be willing to sell me very cheap electricity so long as I'm willing to have it interrupted. My hybrid house allows me to allow that. More on geothermal is at Geothermal Heat Pumps and Saving the World.
Electric storage heat is a way to use only off-peak electricity for home heating. It costs between $3000 and $5000 to install with an existing furnace. However, with heating oil at $3.00/gallon, you need access to off-peak electricity at less than $0.09/kwh for this to make sense – or heating oil needs to go up to $5.00/gallon. On the other hand, residential propane was at $3.11/gallon in Vermont at the end of the last heating season. You only need an off-peak rate for electricity below $0.145 to beat that. People with propane heat ought to take a serious look at electric storage heat now if off-peak electric rates are at all available. Keeping the old furnace means you are ready to take advantage of interruptible rates when the SmartGrid enables them. In many ways using electric storage heat is back to the future; It's Time for Electricity to Come Out of the Closet and Go Into Storage is partly about our experience with it – and its political incorrectness.
Using resistance heating with $0.155/kwh hour electricity is equivalent to paying $5.00/gallon for heating oil. But don't dismiss electric resistance heating just yet. Suppose you had an off-peak rate of $0.08/kwh and only use your resistance heating off-peak; the rest of the time you use your existing oil furnace. Now you're saving money whenever oil is above $2.50/gallon. If oil starts back up, so does the breakeven for electric resistance heating. But, even if you can't get $0.08/kwh electricity, it still may make sense to turn the oil furnace way down at night and put portable electric space heaters (very cheap) just in the living room in the evening and in the bedrooms at night if your house doesn't have separate zones for every room.
Moreover, the Smart Grid should result in very low dynamic rates – hopefully below $.08/kwh. Some home automation is needed so you don't keep getting up in the middle of the night to change heat sources as electric rates change, but that'll all be coming along with the Smart Grid. More on electric resistance heating is at Should You Be Heating with Electricity?
There is a calculator for determining your savings (or loss) from switching to electric resistance or geothermal heating from oil, propane, or natural gas at http://blog.tomevslin.com/heatcalcframe.html.