| 1. Household Energy Demand |
| Annual electricity consumption |
Approximately 2,700–4,000 kWh per year for a typical electrically connected household, excluding unusually intensive loads. |
Use the household's actual 12-month utility data rather than a national average. |
Add the kWh shown on each monthly electricity bill. Separate seasonal use if heating, cooling, or electric water heating is present. |
A reliable consumption baseline prevents the solar array from being significantly undersized or oversized. |
| Average daily electricity use |
About 7–11 kWh per day for the annual consumption range above. |
Calculate both annual average and seasonal daily averages. |
Annual kWh ÷ 365. Compare summer and winter bills because solar production and household demand may peak in different seasons. |
Daily demand helps determine battery capacity and the amount of energy that can be shifted to daylight hours. |
| Hourly load profile |
Many homes use more electricity in the morning and evening, while solar production is normally highest around the middle of the day. |
Measure or estimate electricity use in hourly intervals for at least one representative week in each season. |
Use a smart meter, inverter monitor, or plug-level energy meter where available. |
Loads such as water heating, laundry, dishwashing, and vehicle charging can be scheduled during solar production to improve self-consumption. |
| Peak electrical demand |
Many homes have short-term peaks of approximately 3–10 kW, depending on appliances and heating equipment. |
Confirm the service rating and the highest simultaneous load before adding large electric appliances. |
Review the main service panel, utility data, and nameplate ratings for heat pumps, resistance heaters, ovens, pumps, and chargers. |
Peak demand affects inverter selection, backup-load design, electrical-panel capacity, and whether load management is needed. |
| Future electricity demand |
Electric vehicles, heat pumps, electric water heaters, and induction cooking can substantially increase annual consumption. |
Include expected new loads for at least the next 5–10 years. |
Estimate annual use from equipment power, operating hours, and seasonal efficiency. For example: kW × operating hours = kWh. |
Designing for future loads can reduce the cost of later electrical upgrades and avoid replacing an undersized inverter or service connection. |
| 2. Solar Resource and Roof Potential |
| Peak sun hours |
Solar resource commonly ranges from about 2.5 to 7 peak sun hours per day, depending on location, season, shading, and weather. |
Use a location-specific annual and monthly solar-resource estimate. |
Consult a public solar map or a professional site assessment; do not use a single global average for final sizing. |
Peak sun hours are used to estimate production and reveal periods when backup energy or grid supply may be required. |
| Usable roof area |
Modern residential solar modules generally require approximately 6–10 m² of roof area per kW of installed capacity, depending on module efficiency and layout. |
Measure only unshaded, structurally suitable roof sections after excluding setbacks, walkways, vents, skylights, and fire-access areas. |
Map each roof plane separately and account for orientation, tilt, obstacles, and maintenance access. |
Available roof area may limit system size even when annual electricity consumption is high. |
| Roof orientation and tilt |
Solar modules generally perform best when oriented toward the equator, although east- and west-facing roofs can also provide useful output. |
Evaluate each roof plane instead of rejecting a site based only on its main roof direction. |
Consider annual sunlight, seasonal production, roof pitch, and the household's highest-use hours. |
East-facing arrays may produce more morning energy, while west-facing arrays may better match afternoon and evening demand. |
| Shading exposure |
Shade from trees, chimneys, neighboring buildings, and roof structures can reduce output and may affect part of an array. |
Record shading by season and by hour, especially between approximately 9:00 a.m. and 3:00 p.m. |
Use a shade study, sun-path analysis, or repeated site observations across different seasons. |
Shading can influence module layout, electrical design, tree maintenance, and the value of module-level power electronics. |
| Roof condition and service life |
Solar equipment is intended for long-term operation, while roof coverings may require replacement sooner. |
Repair or replace a roof with insufficient remaining service life before installation. |
Obtain a roof inspection and verify structural capacity, waterproofing, and attachment points. |
Completing roof work first can avoid the labor cost of removing and reinstalling the solar system later. |
| 3. Solar System Sizing |
| Annual solar production estimate |
A 1 kW photovoltaic system may produce roughly 900–1,600 kWh per year, depending on solar resource, orientation, shading, temperature, equipment losses, and system availability. |
Use a site-specific production model with monthly results for final design. |
Basic estimate: system size in kW × local annual yield in kWh/kW = estimated annual production. |
Annual production should be compared with annual consumption, but monthly matching is also necessary because seasonal output varies. |
| Illustrative system-size calculation |
For 4,000 kWh of annual consumption and a local yield of 1,200 kWh per kW, the theoretical array size is about 3.3 kW. |
Actual design may be larger or smaller after considering roof area, export rules, future loads, and economic objectives. |
4,000 kWh ÷ 1,200 kWh/kW ≈ 3.3 kW. |
This calculation estimates energy volume only; it does not guarantee energy independence or full backup capability. |
| Energy offset target |
Common design targets range from partial offset to approximately 100% of annual electricity consumption, subject to local rules and site limits. |
Set the target using annual demand, monthly production, export compensation, and future electrification plans. |
Estimated annual solar production ÷ annual electricity consumption × 100. |
A 100% annual energy offset does not mean the home will operate without the grid at night or during low-sun periods. |
| System losses |
Real systems experience losses from inverter conversion, wiring, temperature, mismatch, dust, shading, and availability. |
Use a production model that includes system losses rather than multiplying rated power by sunlight alone. |
Compare modeled output with the nameplate capacity and local solar resource using conservative assumptions. |
Including losses provides a more realistic basis for sizing storage and forecasting electricity bills. |
| 4. Battery and Backup Integration |
| Battery usable capacity |
Residential batteries are commonly planned in the range of approximately 5–15 kWh of usable energy, although larger systems are possible. |
Select capacity based on evening demand, critical loads, solar surplus, and backup duration. |
Battery capacity should be based on usable—not only nameplate—energy, considering the allowed depth of discharge and system efficiency. |
A battery can shift midday solar energy into evening periods, reduce grid imports, and support selected loads during outages. |
| Backup duration |
A 10 kWh usable battery could theoretically supply a continuous 1 kW load for about 10 hours before conversion and reserve losses. |
Define critical loads first, such as refrigeration, lighting, communications, circulation pumps, and selected outlets. |
Approximate duration: usable battery kWh ÷ average backup load kW, adjusted for inverter losses and reserve limits. |
Whole-home backup may require a larger battery, a higher-power inverter, load shedding, or a backup generator. |
| Battery power rating |
Energy capacity in kWh and instantaneous output power in kW are separate specifications. |
Match continuous and surge power to the critical-load panel and motor-starting requirements. |
List the running and starting power of pumps, compressors, refrigerators, and other motor-driven equipment. |
A battery with sufficient energy may still be unable to start or operate several high-power appliances simultaneously. |
| Battery operating conditions |
Battery performance and available capacity can vary with temperature, charge rate, state of charge, and installation conditions. |
Follow the equipment's temperature, ventilation, clearance, and fire-safety requirements. |
Review the technical documentation and local installation requirements before selecting the location. |
Correct installation conditions support safety, service life, warranty compliance, and reliable backup operation. |
| 5. Integration with Major Home Loads |
| Electric vehicle charging |
Home charging power commonly ranges from approximately 1.4 kW on a standard outlet to about 7.2–9.6 kW on a higher-power residential circuit, depending on the electrical system. |
Use scheduled or managed charging to align charging with solar production and available service capacity. |
Estimate annual charging energy from vehicle efficiency, annual driving distance, and charging losses. |
Managed charging can increase direct solar use, reduce evening grid imports, and limit simultaneous peak loads. |
| Heat-pump heating and cooling |
Heat-pump electricity use varies widely with building insulation, climate, equipment size, and thermostat settings. |
Use measured or modeled seasonal demand rather than a single rated input value. |
Review utility history, equipment specifications, climate data, and heating or cooling degree days. |
Because heating demand may be highest when solar output is low, winter production and backup planning deserve special attention. |
| Electric water heating |
Water heating can be a significant flexible load, particularly in homes that replace fossil-fuel equipment with electric systems. |
Schedule heating during solar-production hours where the equipment and controls permit. |
Estimate demand from household occupancy, water temperature, incoming water temperature, and equipment efficiency. |
Thermal storage in a hot-water tank can sometimes provide lower-cost load shifting without adding battery capacity. |
| Smart controls and load shifting |
Flexible loads may include water heating, vehicle charging, laundry, dishwashing, pool pumps, and selected heating or cooling cycles. |
Prioritize loads that can operate safely without affecting comfort or equipment life. |
Compare the timing of flexible loads with the system's expected midday production profile. |
Control strategies can improve self-consumption and reduce the need for a larger battery. |
| 6. Electrical, Regulatory, and Economic Checks |
| Main service capacity |
Existing residential electrical services may not have enough capacity for solar, batteries, heat pumps, and vehicle charging together. |
Verify service rating, panel space, conductor capacity, grounding, and protection requirements. |
Have a qualified electrician review the load calculation and proposed interconnection method. |
Possible solutions include load management, a panel upgrade, or equipment configured to limit combined demand. |
| Grid export and interconnection |
Export limits, compensation for exported energy, metering, and interconnection procedures vary by jurisdiction and utility territory. |
Confirm local requirements before finalizing system size or battery operating modes. |
Review current utility tariffs, connection rules, permit requirements, and inspection procedures. |
Export restrictions may favor batteries, smart controls, or a smaller inverter even when the roof could accommodate more modules. |
| Critical-load backup design |
Backup systems are often designed for selected circuits rather than every household load. |
Separate essential loads from high-power or nonessential loads before equipment selection. |
Create a load schedule with operating power, starting power, expected runtime, and priority. |
Prioritizing loads can reduce battery size and improve outage duration while maintaining essential services. |
| Performance monitoring |
Monthly production, consumption, battery state of charge, and grid imports provide useful operational data. |
Review performance at least monthly and compare it with the expected seasonal profile. |
Use inverter, meter, battery, and home-energy-management data where available. |
Monitoring can identify shading, equipment faults, unusual consumption, and control settings that reduce savings. |
| Recommended decision sequence |
Energy assessment should precede equipment selection. |
1. Reduce waste; 2. measure demand; 3. assess roof and solar resource; 4. model system size; 5. plan storage and controls; 6. verify electrical and regulatory requirements. |
Use measured consumption and site-specific production estimates for the final design. |
This sequence supports a balanced system that coordinates solar generation, storage, appliances, electric vehicles, and grid interaction. |
Eco Sun Power
