is it more energy/cost efficient to boil a cup of tea in a microwave, or on the stove-top?

Answer 1

Microwave.

Much of the heat of the stove top is simply dispersed into the air. The energy from the microwave is focused inside the oven, and water absorbs microwaves much better than the inside of the oven, very effectively focusing the energy where you want it even more.

If you're air conditioning the house at the time, the difference is even larger, since the air conditioner will have to deal with the waste heat from the stove.

Answer 2

the microwave would be more energy efficiant as the stove gives off heat to the rest of the house. I think an electric kettle is probably best.

Answer 3

Renewable resources are energy efficient.
It may be cheaper to boil water with natural gas, at today's prices, then it is to microwave the same cup of water.

But natural gas is in limited supply, where as electricity, made from solar, wind, or hydroelectric is a renewable resource, and in the final estimate they will be more energy efficient.

Answer 4

Much better in the microwave.