Not directly about a relative, but about her house. :)
My husband's great-aunt built a house when she was in her early 60s: perfect retirement home on a lake, one-story, small, perfect for one person. Mostly solar-heated, it's got HUGE south-facing windows (facing the lake, too - gorgeous view), with thick curtains that you can use to cover the upper half ... so, you open them during the day in winter, and draw the curtains in summer. The house has electric heat and no AC, other than the huge windows. We rented it for 3 months last summer while building our house, and I can confirm that, as long as you close the drapes in summer, it's delightfully cool, and the heating bill was NEVER over 120$/month in winter, not for the past 20 years. Electric rates, for the record, have not gone up in any significant way between last winter and this winter.
She moved into a home recently (she's in her 90s at this point) and the house is now rented by a tenant, who I had a conversation with.
She complained about electric bills for heating during our (terribly mild, honestly) winter. 350$/month, she says (for the record: that's twice the electric/heating bill on my 3-story house...)! She never would have rented the house if she had known how much it would cost, she said!
Turns out: she refuses to open the drapes in the window because 'it will fade the bedspread. IF YOU DO NOT LET THE SUN IN YOU DO NOT GET SOLAR HEATING, AND THEN YOU PAY FOR ELECTRIC HEAT. WTF LADY.
Also, for that kind of money, you could buy a new bedspread every month with the difference in the electric bill!