In the case of things like water heaters and furnaces, they’re going to do stuff that creates a need for more space than the existing equipment occupies, making replacement enormously difficult and expensive in many cases. Count on it.
Marxist Democrats have always had a European fetish: make everything smaller and more expensive.
The last time my natural gas water heater failed, I looked into "flash" heaters. The electric type is small, but requires more power than I have overhead left on my 200 amp service. I looked at a gas fired version. My gas water heater has a 50 gallon tank and a 40,000 BTU burner. The air input and heat exhaust to the roof is built for a 40,000 BTU burner. The flash gas heater has a 128,000 BTU burner. That requires far more air to be delivered to the basement location of the heater and substantially more exhaust capability to avoid buildup of carbon monoxide. The upgrade to the exhaust alone was estimated at over $3,000 15 years ago. Electric fans would be needed to drive the exhaust out at the necessary rate. It was a total non-starter.
On my last vacation to Wales, the bed and breakfast had a shared bathroom. The shower has a 220 volt flash heater for just the shower. If you selected a mild dribble of water, you can get it hot enough to be comfortable. That said, I'm not keen on electrical appliances in my shower.