Short answer: size a solar system in three separate steps: inverter power for simultaneous loads, battery energy for how long loads must run without solar, and PV array power for how much daytime energy you want to generate and recover. Do not size the system from the electricity bill alone.
Step 1: inverter size is about simultaneous power
Add the watts of appliances that may operate at the same time. Then consider starting current for motors and compressors, inverter surge capability and whether high-power loads should remain outside the backed-up circuits.
Step 2: battery size is about energy and runtime
A battery is rated in energy terms, commonly kWh. A 5.12kWh battery does not mean 5.12kW of continuous appliance power for one hour in every real installation. Usable energy depends on allowed depth of discharge, inverter efficiency, battery settings, temperature and system limits.
Step 3: solar panels are about daytime energy production
PV array output varies with irradiance, module temperature, orientation, shading, dirt, system losses and inverter MPPT limits. Panel quantity therefore cannot be selected from inverter size alone.
Whitehouse Summer Solar Load Planner
| Load | Illustrative planning wattage* | Hours/day | Daily energy formula |
|---|---|---|---|
| LED lighting circuit | Enter actual measured/nameplate watts | _____ | W ÷ 1000 × hours |
| Fridge / freezer | Use manufacturer data and account for cycling/startup | _____ | Use measured daily kWh where possible |
| Wi-Fi / networking | Enter actual supply wattage | _____ | W ÷ 1000 × hours |
| Fans | Enter actual product wattage | _____ | W ÷ 1000 × hours |
| TV / computers | Use actual nameplate or meter reading | _____ | W ÷ 1000 × hours |
| High-power loads | List individually | _____ | Decide whether they belong on backed-up circuits |
*Do not use generic internet wattage figures as final design values. Measure or use manufacturer data.
A practical 5kW-class example
A 5kW inverter can theoretically support a substantial group of ordinary household loads, but the actual design depends on simultaneous load, surge current and manufacturer limits. Whitehouse currently stocks equipment such as the Luxpower SNA5000 5KVA Inverter + WiFi, Shoto 48V 5.12kWh Lithium-Ion Battery, Volta 5.12kWh Lithium Battery and WHL&E 585W JA Solar Panel.
For an integrated option, Whitehouse also lists the Luxpower SNA6000 Hybrid Inverter with Volta 5.12kWh Lithium Battery.
Why summer loads are different
Summer often increases daytime cooling loads. Eskom describes the summer system profile as relatively high for much of the day, with air conditioning, geysers and pool pumps contributing to demand. For a solar household, the coincidence between daytime sun and daytime loads can be useful because some energy can be consumed as it is produced.
Fans are especially friendly loads for backup systems compared with resistance heating, but actual fan wattage still matters. Refrigerators and pumps need additional attention because motors can have starting current above their normal running power.
Do not put every load on the battery
It may be technically possible to connect a large appliance, but that does not mean it is sensible. Electric geysers, ovens, tumble dryers, space heaters and similar high-power appliances can consume battery energy very quickly.
Design essential and non-essential circuits deliberately. The final distribution-board arrangement should be completed by an appropriately qualified person.
Solar registration and compliance in South Africa
Eskom's current guidance says grid-connected embedded generation must be registered with the relevant licensed distributor. On 30 September 2026, Eskom extended its waiver of registration-related charges for eligible customer-owned systems up to 50kVA connected directly to its network until further notice. Municipal customers must follow the requirements of their own licensed distributor. See Eskom's September 2026 update.
Eskom also provides an updated two-step SSEG registration and authorisation process and states that grid-tied systems must be evaluated for applicable technical compliance. See the SSEG registration guide.
Protection and balance-of-system equipment matter
A solar quotation is more than an inverter, battery and panels. It can require appropriate isolators, breakers, surge protection, fuses, cable, distribution-board work, mounting and labelling.
Examples from the current catalogue include the WHL&E Solar Combiner Box 3 In 1 Out, Chanan 2P 20–40kA 600V DC Surge Arrester and mounting accessories such as the WHL&E Roof Clamp Long.
Information to send Whitehouse for a useful solar quotation
- recent electricity bill or prepaid usage information;
- list of essential appliances and actual wattages where available;
- required backup duration;
- single-phase or three-phase supply;
- photos of the DB and meter;
- roof photos, orientation and shading;
- existing inverter, generator or solar equipment;
- available battery/inverter location;
- delivery location and access constraints;
- budget and future expansion plans.
Use the rest of the summer plan to reduce the system you need
Solar sizing should not happen in isolation. Reducing unnecessary summer loads can reduce battery and inverter pressure. Read How to Reduce Your Electricity Bill This Summer and Summer Storm Electrical Safety as companion guides.
Frequently asked questions
Does a 5kW inverter need exactly 5kW of solar panels?
No. Inverter AC output and permitted PV input are different specifications. PV string sizing must follow the inverter's MPPT voltage/current limits and module electrical data.
How many 585W panels make 5kW?
A simple nameplate calculation is 5000 ÷ 585 ≈ 8.55, but a real array cannot be selected from that division alone. The number of modules must satisfy inverter voltage/current limits, roof space, string design and expected energy requirements.
Can Whitehouse help with solar product selection?
Yes. Whitehouse's current contact information states that the team assists with solar and backup-power enquiries, product information and quotations. Final electrical work and system design should be undertaken by appropriately qualified professionals where required.
Technical note: product selection and calculations in this guide are planning information, not a substitute for site-specific electrical, engineering or solar design. Fixed electrical work should be carried out and certified by appropriately qualified persons where required.
Need it before the next hot spell?
Whitehouse Lighting & Electrical dispatches from Trichardt, Secunda and delivers throughout South Africa. Eligible paid, in-stock weekday orders placed before 15:00 are ordinarily dispatched the same working day. Typical delivery is approximately 1–3 working days to main centres and 2–6 working days to regional or outlying areas.
Qualifying standard-size orders of R1,500 or more receive free standard delivery. Oversized, heavy, battery, solar-panel and special-freight products may require a separate delivery arrangement. See the current shipping policy for full terms.
Request a solar or backup-power quotation from Whitehouse Lighting & Electrical.
