Should I run my dishwasher and washing machine on solar in South Africa?

Why wet appliances beat export theatre

If a wash uses 1.8 kWh at midday under PV, at ~400 c you avoid ~R7.20 of import. Exporting that 1.8 kWh at ~153 c Cape-style credit is ~R2.75. Multiply by five cycles a week and self-use wins quietly every month. Fixed wires charges still appear on the bill — timers do not delete them — self-consume vs export · fixed charges · metro tariffs.

Heat is the kWh — cold washes and eco programmes

Most of a cycle’s energy heats water or air. Eco / 40 °C programmes, cold washes where fabric allows, and full loads cut kWh before solar enters the chat. Heat-pump tumble dryers use less than old resistive dryers but still deserve sun-hour scheduling. Drying on the line remains the cheapest “battery.”

Timers, apps and inverter surplus modes

• Simple delay-start to 10:00–14:00 on sunny days.
• Smart plugs with solar-surplus automations where the hybrid ecosystem supports them.
• Manual “only when the app shows PV > house” discipline for households that dislike gadgets.

Pick one method and teach the family; mixed rules create night-time surprises — how solar works.

Coincidence loads on 5 kW hybrids

Dishwasher heater + kettle + pool pump + geyser element is how midday trips happen with a handsome roof. Stagger wet appliances after the geyser’s main boost, or use a PV diverter for the element and run laundry later. EV charging should yield to laundry if the hybrid is near its ceiling — pool pump · geyser · EV from solar.

Backup-board policy

Default: dishwasher and washing machine on non-essential/main. They can wait a Stage slot; fridges cannot. Exceptions are rare (medical laundry needs) and must show kW/kWh on the quote — fridge on backup · backup sizing.

Prepaid and TOU footnotes

Night-time heated cycles on prepaid burn tokens fast. On TOU / Homeflex / Cape Residential TOU, peak-window laundry is an own-goal even with panels. Align delay-start with off-peak or solar windows after any tariff change — TOU habits · Cape Town TOU · prepaid + solar.

Worked month sketch

Eight dishwasher cycles × 1.5 kWh + twelve laundry cycles × 1.2 kWh = 26.4 kWh/month. At 400 c self-used under PV ≈ R106/month avoided versus ~R40 if the same energy had only earned ~153 c export. Small money beside a geyser, large money beside “we never touch timers.”

Owner checklist

• Delay-start or surplus automation enabled.
• Eco/cold programmes default.
• Wet appliances off lean Stage board.
• Stagger written vs geyser/pool/EV.
• Re-check after tariff or SSEG changes.

Rentals, domestics and household SOPs

Timers fail when five people override them. Put a one-page SOP on the laundry door: sun-window hours, eco programmes, no dryer before 11:00, Stage = no wet appliances. Domestic workers and tenants deserve the same briefing as the family who signed the quote — especially in holiday homes and Airbnbs — guesthouse solar · holiday home.

If the hybrid app supports load prioritisation, put wet appliances below fridge and ICT so an automation cannot starve essentials. Test that priority on a sunny Saturday with a forced Stage simulation.

Hard-water, filter and maintenance footnotes

Blocked filters and failed heating elements stretch cycles and waste kWh. Maintenance is tariff work. Softener salt and descale routines belong beside solar SOPs in hard-water metros. A machine that runs 30% longer because of neglect quietly taxes your PV surplus.

Stacking with heat pumps and EV

Whole-home electrification (heat pump + EV + wet appliances) needs a daytime choreography chart. Heat-pump water at 10:00–13:00, laundry 13:00–15:00, EV when the car arrives if surplus remains. Without a chart, the 5 kW hybrid spends the afternoon faulting — heat pump + solar + EV · install order.

Payback models should show wet-appliance self-use as a line item when families claim “we already shifted everything.” Many have not. Audit the app before buying more modules for export income.

Programme kWh ranges worth measuring

Use a plug meter for three cycles: eco dishwasher, mixed laundry 40 °C, and your worst “intensive” programme. Many households discover the intensive cycle doubles kWh. Put eco as default in the machine settings, not only on a sticky note. Cold rinse + line dry often beats any solar automation.

If you add a heat-pump dryer later, repeat the meter test — marketing kWh/cycle figures assume ideal load sizes. Schedule it inside the PV window or off-peak TOU bins only.

Export audit: open the hybrid app at 12:30. If you are exporting >1 kW while both wet appliances are idle and the geyser is cold, you have free self-use capacity today. Run a load. That habit compounds more monthly rand than arguing about module brands — bill still high · monthly savings · hybrid brands.

Finance note: when modelling payback, include behavioural self-use only if timers are installed and demonstrated at handover. Otherwise use a conservative self-use fraction — solar finance · payback.

School mornings vs sun windows

Uniforms do not wait for peak irradiance. Pre-wash on Sunday sun, or use delay-start overnight into an early PV window, rather than 05:30 heated cycles on prepaid/TOU peaks. Boarding-school trunks and sports kit weeks are when families abandon timers — put a calendar reminder beside the machine for those spikes.

If the hybrid supports a “surplus only” relay for the dishwasher, commission it and test with a kettle load first. Surplus automations that fight the geyser diverter need a priority order in writing.

Print the owner checklist, paste your real tariff cents beside it, and refuse any quote that cannot show the same arithmetic with your bill as the input. Solar News 24 pages are education — confirm every figure on the live municipal or Eskom PDF and on the installer datasheet before you pay a deposit. When in doubt, prioritise daytime self-use against retail rates, then Stage essentials hours, then export credits.

• Tariff name and date on the brief.
• Flexible loads listed with sun-hour plans.
• Essentials board drawn with watts.
• Usable battery kWh and hybrid backup kW stated.
• SSEG / CoC / meter responsibilities named.
• Portal access and a loaded test before final payment.

Timer discipline beats bigger arrays

Two delayed-start cycles into sun hours can shift more kWh than an extra panel you export at ~143–185 c. Pair with monitoring so midday import still flags a failed timer — monitoring · City Power credit · eThekwini.

Quick questions

Can I put the washing machine on the backup board?

You can, but it is rarely wise on lean Stage designs. Prefer fridge/ICT/lights; finish laundry when the grid or PV returns.

Do dryers belong in the sun window too?

Yes if you must use one — especially resistive dryers. Heat-pump dryers still deserve scheduling; line-dry when weather allows.

Sources

• Solar News 24 — self-consume vs export
• Solar News 24 — metro tariffs
• Solar News 24 — costs & savings