Options for a low income household with no Air Conditioning

Does anyone know if there are any programs for low income households (elderly) to replace central air conditioning unit in their house? They are in Harris county. Their units died years ago, they have a small window unit in their bedroom which is at its end of life. It would be miserable inside their house during peak summer months when we have 100 degrees weeks at a stretch. I want to know if there are any resources out there that could help them. TIA!