Vận hành, TOU & quản lý năng lượngOperation, TOU & energy management · BàiLesson 3/4
Electricity Consumption Behavior and Self-Consumption
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Solar Knowledge HubHành vi dùng điện và tự tiêu thụLoad profile & self-consumption
Hệ chỉ tiết kiệm tốt khi sản lượng khớp với cách khách dùng điện, hiểu load profile là cơ sở để thiết kế đúng.A system saves well only when generation matches how customers use power, and understanding the load profile is the design foundation.
| Thiết bịAppliance | Công suấtPower | Giờ/ngàyHours/day | Điện năng/ngàyEnergy/day |
|---|---|---|---|
| Điều hòa 12.000 BTU (không biến tần)AC 12,000 BTU (non-inverter type) | 1.200 W1,200 W | 8 giờ8 h | 9.6 kWh9.6 kWh |
| Tủ lạnhRefrigerator | 150 W150 W | 24 giờ24 h | 3.6 kWh3.6 kWh |
| Đèn (thường)Lighting (standard) | 750 W750 W | 1 giờ1 h | 0.75 kWh0.75 kWh |
| Đèn LEDLED lighting | 60 W60 W | 5 giờ5 h | 0.30 kWh0.30 kWh |
| Máy tínhComputer | 120 W120 W | 8 giờ8 h | 0.96 kWh0.96 kWh |
| TổngTotal | 15.21 kWh15.21 kWh |
Mức tự tiêu thụ trên 80% chỉ đạt được khi có pin. Không nên hứa con số này cho hệ không pin.Self-consumption above 80% requires a battery. Never promise this figure for a battery-free system.
Lệch pha giữa nắng trưa và đỉnh tải tối là lý do kỹ thuật cốt lõi khiến pin có giá trị với nhà dân. Cơ sở sản xuất và văn phòng đỉnh ban ngày tự khớp với nắng, tỉ lệ tự tiêu thụ cao ngay cả không pin, và pin với họ chủ yếu để né giá cao điểm buổi tối hoặc dự phòng.The phase mismatch between midday sun and evening home peak is the core technical reason batteries add value for homes. Businesses and offices peak during the day, matching the sun, so they achieve high self-consumption without a battery, and add one mainly to avoid evening peak prices or for backup.
Với khách hộ gia đình: giải thích bằng load profile của chính họ, đỉnh tối lệch pha nắng trưa, không pin thì phần lớn điện trưa bị phí, pin lấp đúng khoảng lệch đó. Với khách doanh nghiệp dùng ban ngày: nắng tự khớp tải, có thể bắt đầu không cần pin, pin thêm sau để tối ưu TOU.For home customers: use their own load profile, evening peak mismatches midday sun, without battery most midday energy is wasted, battery fills that gap. For daytime businesses: sun matches load, so they can start without a battery, add one later for TOU optimisation.
A solar energy system only saves money effectively when its generation matches how the customer uses power. Understanding consumption behavior (known as the load profile) is the foundation for designing the right system and maximizing the self-consumption ratio. This document explains load profiles, how to collect the data, and why aligning the load with sunlight determines overall system performance.
For: survey and design technicians, sales staff explaining why a load survey is necessary, and newcomers who need to understand electricity consumption behavior.
Quick Summary
A load profile is a chart of electricity consumption by hour of the day, showing when the customer uses the most and least power. Residential households typically peak in the evening, while factories and offices peak during the daytime.
Solar generation is most abundant around midday, so a household with an evening peak is out of phase with the sun. This is why residential customers need a battery to shift midday energy to the evening, while daytime businesses naturally align with the sun far more effectively.
The self-consumption ratio is the share of solar electricity used on-site rather than wasted. Without a battery, this ratio is typically only 25 to 40 percent; with a battery it can reach 60 to 90 percent.
What Is a Load Profile
A load profile is a chart showing the level of electricity consumption over time throughout a single day. It reveals the customer’s power usage habits and serves as the basis for selecting the right panel capacity, inverter size, and battery capacity to match demand, thereby optimizing cost.
The shape of a load profile varies by customer type. Residential households have a consumption peak in the evening when everyone returns home and uses air conditioning, cooking appliances, and entertainment, while consumption is low during the day when people are out. Factories and offices are the opposite: their peak occurs during working hours in the daytime and drops off at night. This is the core difference that determines the role of a battery.
Collecting Load Profile Data
To obtain an accurate load profile, real measurements are needed using a smart meter or data-logging device, or the profile can be estimated from a device inventory. The estimation method involves listing each appliance with its power rating and daily usage hours, then calculating the energy consumption.
| Appliance | Power Rating | Hours per Day | Energy per Day |
|---|---|---|---|
| 12,000 BTU Air Conditioner | 1,200 W | 8 | 9.6 kWh |
| Refrigerator | 150 W | 24 | 3.6 kWh |
| Lighting | 750 W | 1 | 0.75 kWh |
| LED Lighting | 60 W | 5 | 0.30 kWh |
| Computer | 120 W | 8 | 0.96 kWh |
| Total | 15.21 kWh |
One important note: the 1,200 W figure for the air conditioner applies to a conventional non-inverter unit. Modern inverter air conditioners have variable consumption and average significantly lower, so during a site survey it is better to measure actual power draw rather than rely on the nameplate rating. Data should be collected over 7 to 14 days to get the most representative results, since weather, temperature, and usage habits all have an impact.
Aligning the Load with Sunlight and the Self-Consumption Ratio
This is where the load profile meets the solar generation curve. When the load curve and the solar output curve are plotted on the same chart, the area lying below both curves represents solar electricity consumed directly: this is self-consumption. The surplus solar energy when generation exceeds load (and no battery is present) is wasted, while the shortfall when load exceeds generation must be purchased from the grid.
The self-consumption ratio is the share of solar electricity used on-site divided by total generation: the higher, the better. It is important to be realistic about this figure. A system without a battery, where a residential household’s evening peak is out of phase with midday sun, typically achieves a self-consumption ratio of only about 25 to 40 percent. Adding a battery to shift midday energy to the evening can raise this ratio to approximately 60 to 90 percent. The figure above 80 percent cited in some references is only achievable with a battery: it is not the default.
The phase mismatch between midday solar generation and a residential household’s evening load peak is the precise technical reason why batteries have real value for homeowners. Commercial and industrial facilities with daytime peaks naturally align with the sun, so they achieve a high self-consumption ratio even without a battery; for them, a battery serves mainly to avoid time-of-use peak tariffs in the evening or to provide backup power. Understanding this distinction enables better-targeted battery recommendations.
When a residential customer asks whether they need a battery, walk them through their own load profile. A home that uses most of its power in the evening while peak sunlight occurs in the middle of the day will waste most of its midday solar (or sell it back cheaply) while still buying expensive grid power at night. A battery fills exactly that gap. For a business customer with daytime consumption, the situation is reversed: the sun naturally matches the load, so they can often start without a battery.