1. About Working State
| Item | Value | Remark |
| Best working point | 1350W（input power） | Q=5980m³/h，P=992Pa，η=90% |
| Working time | 8760h per year | 24h continuously：24×365=8760h |
| Electricity charge for industry | 0.65 yuan /kWh | |
| Maintenance cost factor | 1% per year of purchasing cost | There is no wearing part of EC fan, so maintenance cost is very low. |
2. Calculation of Annual Energy Consumption
2.1 Annual Energy Consumption Of EC500
E_1 = P_1 \times T \times \frac{1}{1000} = 1350W \times 8760h \times 0.001 = 11826kWh
2.2 Annual Electricity Charge
| Model | Annual energy consumption（kWh） | Annual electricity charge（0.65 yuan /kWh） | Electricity charge in 5 years |
| EC-500 | 11826 | 11,826×0.65≈7687 yuan | 7,687×5≈38,435 yuan |
| Matching AC Model | 19710 | 19,710×0.65≈12,812 yuan | 12,812×5≈640,60 yuan |
2.3 Maintenance Cost
Suppose purchasing cost for one set of EC500 is 18,000 yuan, purchasing cost for one set of matching AC model is 12,000 yuan：
- Maintenance cost of EC500：18000×1% = 180 元（only for cleaning）
- Maintenance cost of AC model：12000×3% = 360 元（for bearing check and control modular rectification）
3. Energy Saving and Payback Period
3.1 Relative Energy Saving
| item | 1 year | 5 years | 10 years |
| Electricity charge | 12,812 – 7687 = -5,125 yuan | -25,625 元 | -51,250yuan |
| Maintenance cost | 360 – 180 = -180 yuan | -900 yuan | -1800 yuan |
| In total | -5,305 yuan / year | -26,525 元 | -53,050 yuan |
3.2 Payback Period
Purchasing Cost Difference：18,000 – 12,000 = 6000 yuan
Payback Period= purchasing cost difference ÷ annual energy saving = 6000 ÷ 5227 ≈ 1.13 year
Conclusion: 14 months is enough to get payback for purchasing cost difference and total saving in the rest 8.87 years will be 47,055 yuan
