First cost is the easiest number to read and the worst number to decide on. The real cost of a heat exchanger is the sum of purchase price, the energy it saves or wastes over its life, maintenance, and eventual replacement, all brought to present value. That is the life-cycle cost (LCC), and it is the only number that survives contact with a 15-year operating budget where the energy term repeats every hour.
The LCC equation
LCC = first cost + present value of energy + present value of maintenance + replacement - residual value. Discount the future cash flows at a 5% to 8% rate over a 15 to 20 year service life. A higher-effectiveness core costs more up front but shifts the energy term down by far more, and because the energy term recurs for two decades it dominates the total, often by an order of magnitude over the purchase price.
Worked example: two 10,000 m3/h cores
Core A is 65% effective at $4,000; Core B is 82% effective at $6,500. The extra 17 points recovers roughly (10000 x 1.2 x 1.005 x 25 x 0.17) / 3600, about 14 kW of heating at a 25 degrees C lift. At $0.12/kWh and 2,000 heating hours per year that is 28,000 kWh, or $3,360 per year. The present value of that saving over 15 years at 6% discount is about $32,700, against a $2,500 price gap, so Core B wins decisively even before counting the smaller summer cooling saving.
| Item | Core A (65%) | Core B (82%) |
|---|---|---|
| First cost | $4,000 | $6,500 |
| Annual energy saved | base | +$3,360 |
| PV of energy (15 yr @6%) | base | +$32,700 |
| Annual maintenance | $200 | $200 |
| 20-yr LCC | higher | lower |
Items people forget, and sensitivity
- Pressure drop: a core 30 Pa tighter costs fan energy every hour it runs, a recurring charge the LCC captures but the quote does not, so always model it in the fan-energy model.
- Maintenance: a plate core needs an annual wash (~$200); a wheel adds a motor and belt (~$150/yr) but recovers more latent energy, a trade worth the math.
- Residual: stainless or epoxy-coated cores in corrosive streams outlast plain aluminium, raising the salvage and avoiding early replacement that wrecks the LCC.
Run a sensitivity check because the LCC answer is only as good as its inputs. At a 4% discount rate the energy saving is worth more in present terms than at 8%, which can flip a marginal custom core from reject to accept; over a 20-year life instead of 15 the same saving compounds further. Test the two or three assumptions that move the result most, usually the energy price, the operating hours and the discount rate, and report the range rather than a single false-precision number. Build the LCC before you buy, then sanity-check it with the payback calculator and the broader economics guide. Keep the core washable per the maintenance guide so the energy term holds for the whole life, and choose materials from the materials guide to avoid an early failure that blows up the total cost.
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