Three areas need attention, lighting, heating and cooling. There are answers for all of them.

Gone are the days when you can do what you want with heat and light and only pay a small bill monthly. Power costs have risen and will keep rising and the only real way to fix this is to build in some passive and active solar engineering processes to replace our previous filthy habit of burning things to inefficiently generate very expensive AC power.

cooling

Cooling is the easisest to add, although this may apply more to those outside the UK. Look up "Solar Chimney". You can make one of these from some wood, glass and black paint. Once that's up you have a chimney,driven by the sun. When it heats up when the sun is shining, air moves up the chimney. You have that draw from the room you want to cool. Next a 6" hole is bored from that rooms floor, at 45 degree angle and long enough to clear the room for a few feet. Where it does another hole is bored straight down about 8 to 12 feet or so. With this open the room with the solar chimney will pull air through here. Four feet down it's always 50F no matter where you are. So, all you have to do is vent the hot air out and pull in cool air from underground.


heat

To conserve summer heat at night, place as many large clear bottles of water everywhere. With enough in full daylight they will heat up by day and give off heat at night. For heat in cool months, you have the Greenhouse Effect going for you. If you heat up 10,000 gallons of water with the sun in a greenhouse, them pump it under the house with a solar powered pump then pump it back into the greenhouse at night to let that heat out you won't need to pay for additional heat for the greenhouse. A professor of Mech. Eng at Rutgers university in America did this in the 1980s and to date he's not spent any money to heat his greenhouse. That story was written up and documented pretty well. Unlike the "pay as you go" plan of monthly installments to the power company the costs here are all up front, but after that there's no bills for a much more reliable way of doing all this.



light

For light, you'll have use solar panels, some sort of battery array, whether a lithium powerwall, lead acid array or one great big lead acid battery ex telco. After that it's just a question of balancing lights, and solar panels. LED has evolved such that you can now walk into a hardware store and buy a 400 Watt "Garage" light (that really draws 85 watts). Two of those will lightup a room. This part is a bit pricey but once installed it's free to run.