This from the Choice review of front-loading washing machines (which are generally more efficient and tend to have cold-only inlets):
Front loaders generally offer more temperature options than top loaders because they use an internal heater rather than hot water from the tap (which is a maximum of 65 degrees).
So while most front loaders don’t have a hot water inlet, they can comfortably wash at up to 90 degrees (which is partly why you can’t open the door mid-cycle). While heating water this way is more expensive than using off peak electricity or solar, the low volume of water used means top loaders are still cost effective to run, even on hot cycles.
The down-sides, according to Choice is that they are a bit noisier and can take two to three times as long to wash a load.
Swings and roundabouts … but as Austman observes, a better alternative than re-plumbing the block.