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Table 1 Return on investment

From: Making healthy homes? A pilot study of the return on investment from an external wall insulation intervention

Costs (£) Benefits (£) ROI
Project implementation = £4539.50 (cost of installation per house) * 2252 (# of households receiving EWI) = £10,222,954 Adjusted monthly difference in fuel expenditure (early cladders-control) 40 Annual adjusted difference between treatment and control group * total households £40 * 12 * 3256 = £1,562,880  
Maintenance = £0 (over first 4 years of installation) Adjusted difference in EQ-5D-3L score (early cladders-control) 0.01 Adjusted Difference in EQ-5D-3L score * NICE QALY threshold * total households 0.01 * £20,000 * 3256 = £651,200  
  Adjusted difference in usage * cost of health care (early cladders-control): outpatient appointments/hospital visits (£4,185,665–£3,111,284) Medical procedures: (£887,609–£1,159,201) Medication: (£60,254–£4,438,493) Sum of adjusted difference in health care costs between early cladders and control:  £695,035  
Total costs = £10,222,954 Total benefits = £1,519,045/year or £6,076,180 for 4 years ROI (%) = (benefits-costs)/costs =  41%
  1. Total amounts are in italics