Hi
we (my wife and I) host here in very rural Spain. Electricity as such is reasonable but the fixed connection charge up to a max power, which is tightly controlled, is expensive. One house is slightly on the luxurious site with a jacuzzi on the balcony, air con/heating (heat pump), electric boilers and ceran cooking hob but we use some simple electronics that limit parallel usage. Cooking or washing switches off the jacuzzi. Air Con / heating switches off for a while when there is still too much power used (like both hair dryers on full blast) and the boilers only really have a chance at night or when the people are out. So we manage with 4.8Kw max load. We explain this to the guests (often blame it on the rural setting and the power company which helps) and so far it does work.
Waterboilers have the advantage that the water simply gets progressively cooler giving ample warning to get on with it.
Water comes from our own wells and is reintruduced by our own sewage systems. One advantage of having very soft water or using a water softner is that guests tend to use much less soap / champoo / detergent, specifically when they have tried to get rid of a foamy head under progressively cooler water.
Again we do explain this.
We also explain to our guests that a toilet is not a general waste disposal and usage of agressive chemicals may kill billons, good bakteria that is.
One house has supporting solar panels but here in Spain one is not allowed to feed the excess into the grid ...... So, yes, sometimes in summer the decision is either run an air con or the underfloor heating (Bathrooms) might come on ....
We also have forced ventilation in the bath rooms. A slightly noisy vent (not loud but you do hear it) comes on when the humidity is above a certain point - interestingly guests find out fast that opening the window cuts the running time ..... This with the above mentioned low wattage underfloor warming keeps these bathrooms dry and avoids the usual humidity problems.
I'm not worried about lights as with advanced LED the total wattage is about the equivalent of two old 60Watt bulbs per house and we rather have a couple of 3 watt leds on than worrying about sensors and when is dusk or where to position a switch.
But what we did is every light and all sockets are on a remote. These have a an "all out" button and chanel 1 button 1 is a welcome setting. Works like a charm. Yes, there is a switch at each door but it just does the welcome setting. Total usage on standby is 7,5 Watt which includes TV etc. These remot(es) have fixed slide in places in the houses and we explain that without them nothing will work. Amazingly they are still there.
We have also put moskito netting in some windows and fly screens on doors to encourage natural ventialtion.
Just some greenish ideas from Galicia / Spain
M