Designing a reliable all-in-one solar street light requires a balanced match between solar panel power, actual lighting demand, and usable battery energy.
Start with the lighting task and daily operating schedule. Then check whether the energy system can support that schedule through the design season and recover after low-sun periods. An integrated enclosure must also have room for the selected components and provide suitable thermal and service conditions.
1. Define Your Design Requirements
Before selecting components, confirm these parameters:
- Installation location, design month, and panel orientation: use local solar-resource data and survey seasonal shading. Peak sun hours are equivalent full-irradiance hours, not simply the time between sunrise and sunset.
- Required lighting schedule: record the actual input power and duration at each dimming level, including motion-triggered operation where used.
- Backup target: define the required days, permitted lighting mode, starting battery state of charge, and low-sun assumptions for the project.
- Mounting height and lighting area: also record road width, pole spacing, optics, maintained illumination, uniformity, and glare requirements. Height alone cannot determine LED power.
- Environmental and service conditions: document temperature, wind and corrosion exposure, access for battery replacement, and the project’s applicable design requirements.
The lumens and wattage guide explains how photometric performance affects the lighting load used in the energy calculation.
2. Core Matching Principles
Calculate daily load energy first
Use E_daily = Σ(P_i × t_i), in Wh/day. Each P_i is the measured or documented electrical input power in watts for a load or operating stage; t_i is its daily operating time in hours. Add all loads and stages without counting any load twice.
For the formulas below, define E_daily at the inputs of the luminaire and other powered devices. Luminaire input includes its driver consumption. Include controller standby power, sensors, and optional cameras or communication equipment where they draw energy. Cameras and communications may operate during the day as well as at night. State whether ancillary consumption is included in a measured system total or added separately.
Use measured power at each programmed setting: a brightness percentage is not necessarily the same percentage of electrical power. A motion-controlled system also needs an agreed traffic or trigger assumption.
Size the panel for daily energy balance
The preliminary relationship is:
P_PV = E_daily / (PSH_design × η_system)
P_PV is panel rated power in W. PSH_design is design-month peak sun hours per day for the proposed panel plane. η_system is a dimensionless allowance for losses between rated panel energy and the defined load boundary, including the applicable charging, storage, wiring, and delivery losses. Document which losses it includes and avoid counting the same loss again elsewhere.
The unit check is (Wh/day) / (h/day) = W. Battery voltage does not belong in this panel-power denominator. Shading, temperature and other derating assumptions must be documented; do not apply a second allowance for a loss already included in the solar-yield estimate.
This relationship screens ordinary daily energy balance. It does not, on its own, establish recovery after an extended cloudy period.
Size usable and nominal battery energy
For a preliminary backup case with no new solar contribution, use:
E_battery_nominal = E_daily × N / (DoD_usable × η_discharge)
N is the specified backup duration in days at the stated operating profile. DoD_usable is the fraction of nominal energy permitted for use. η_discharge accounts for discharge and delivery losses to the same load boundary used for E_daily. The result is nominal battery energy in Wh before additional design allowances for temperature and aging.
Convert energy to nominal ampere-hours only after choosing a compatible battery voltage:
Capacity_Ah = E_battery_nominal / V_nominal
If consumption is measured at the battery terminals instead, redefine the energy boundary and efficiencies accordingly; do not apply the downstream delivery losses a second time. Actual usable energy must be checked against the battery and BMS limits, operating temperature, discharge rate, and end-of-design-life capacity requirement.
Use each efficiency factor only within its stated calculation. The example below shows how the panel-energy and battery-storage checks share the same load boundary.
Check recovery charging separately
Choose an acceptable recovery period after the design low-sun event. For each recovery day, estimate solar energy available at the battery boundary, subtract the ongoing load expressed at that same boundary, and apply the relevant charging losses and limits to the remainder. Check whether the net energy over the recovery period restores the specified state of charge.
A larger battery does not guarantee it will recharge before the next low-sun event. Simply multiplying daily panel demand by the number of backup days does not define the recovery period or continued lighting load. Cloudy weather can still produce some energy; use a time-based resource and load model when the project requires a more detailed assessment. The cloudy-day autonomy guide explains the operating assumptions behind a backup claim.
Worked Example: From Daily Wh to Panel W and Battery Ah
Illustrative assumptions only: the following values describe a calculation exercise, not a NEWSKYPOWER model or a recommended project configuration. Assume luminaire input of 30 W for 4 hours and 10 W for 8 hours, plus a separate 1 W auxiliary load for 24 hours. The luminaire figures include the driver; the auxiliary load is not included in those figures.
- Daily load: (30 × 4) + (10 × 8) + (1 × 24) = 224 Wh/day.
- Panel screening: assume 4 peak sun hours/day and a system efficiency of 0.70 to the defined load boundary. 224 ÷ (4 × 0.70) = 80 W of nominal panel power for ordinary daily balance.
- Battery screening: assume 2 days with no solar contribution, a fully charged starting battery, a usable discharge fraction of 0.80 and discharge-side efficiency of 0.90. (224 × 2) ÷ (0.80 × 0.90) = 622.2 Wh of nominal storage, rounded.
- Convert to Ah: at an assumed compatible nominal battery voltage of 12.8 V, 622.2 ÷ 12.8 = 48.6 Ah, rounded.
The 0.70 panel factor already includes the relevant discharge losses; do not multiply it by 0.90 again. The 0.90 factor is used separately to estimate nominal storage. These screening values exclude additional temperature and ageing allowances, and the 80 W result provides no planned recovery surplus. Final selection needs a recovery calculation, actual component ratings, controller compatibility, physical fit and a lighting design.
3. Review the Proposed Engineering Configuration
Build the configuration from verified inputs rather than assigning a wattage and battery to a pole height. Use this review table before accepting a supplier proposal:
| Design item | Evidence to review | What the review determines |
|---|---|---|
| Luminaire and layout | Offered-model photometric file, measured watts and lumens, road dimensions and lighting calculation | Optics, layout and actual power needed for the lighting task |
| Operating program | Input power at each stage, durations, motion assumptions and ancillary loads | Daily energy in Wh at the stated boundary |
| Solar panel | Rated power and test conditions, local design-month resource, orientation, shading and loss assumptions | Daily generation and charging adequacy |
| Battery | Nominal V, Ah and Wh, usable discharge limits, temperature data and aging allowance | Usable energy and backup performance |
| Recovery | Starting deficit, continuing load, solar profile, permitted recovery time and charging limits | Whether the battery can regain its target state of charge |
| Integrated assembly | Component dimensions, thermal design, wiring, controller limits, mounting and service instructions | Whether the selected configuration fits and can be operated and maintained |
4. Professional Design Recommendations
- Compare panel rated power, dimensions and documented efficiency at the same test conditions. Select a panel that fits the mounting design and the controller’s electrical limits.
- Evaluate the offered battery chemistry and pack specification. For a LiFePO₄ option, verify its BMS, permitted charge and discharge temperatures, usable energy and service instructions; chemistry alone does not prove outdoor lifetime.
- Use programmed power management only where the proposed lighting levels satisfy the project’s requirements. Include every operating stage in the energy calculation.
- Check the enclosure, seals, thermal design, corrosion resistance and mounting documentation for the actual site. An IP rating addresses specified ingress tests, not battery endurance or resistance to every outdoor condition.
For a configuration review, provide Newskypower’s solar street light team with the location, road or area drawing, pole layout and height, lighting criteria, full operating schedule, backup target, and site constraints. Request the supporting photometric and energy calculations with the proposed components.
FAQ About All-in-One Solar Street Light Design
How do you design an all-in-one solar street light?
Define the lighting criteria and layout, determine actual daily load energy, and use local design-month solar data to screen panel and battery capacity. Check recovery charging, temperature, optics, and integration before approving the configuration.
How do I calculate the battery capacity for a solar street light?
Use daily Wh, the required backup profile, permitted depth of discharge, and discharge losses to estimate nominal Wh. Then divide by nominal voltage to obtain Ah. Adjust the boundary if the load is measured at the battery, and check temperature and aging allowances.
How do I choose the solar panel size for a solar street light?
Divide daily load energy by design-month peak sun hours and the relevant system efficiency. Then separately verify recovery charging, panel orientation, shading, and controller compatibility. Panel size must also fit the physical design.
What battery is best for all-in-one solar street lights?
Choose a documented battery pack that meets the required usable energy, temperature, protection, and service needs. LiFePO₄ is an option, but the chemistry name does not replace pack-level evidence.
How many hours can an all-in-one solar street light work?
Runtime depends on available battery energy, actual load, operating mode, and charging conditions. An all-night requirement must be checked for the design season and the intended brightness schedule.
How many cloudy or rainy days can a solar street light support?
There is no universal backup duration. Define the project’s weather and operating assumptions, then verify usable stored energy, expected solar contribution, and recovery between low-sun periods.
What information does a manufacturer need to design a solar street light?
Provide the location, road dimensions and pole layout, lighting criteria, operating program, backup target, environmental conditions, and maintenance requirements. Ask the manufacturer to identify the assumptions and calculations supporting the proposal.
