Solar-use planning series · 6-minute read · Updated 5 October 2026

A high electricity bill can make solar worth investigating, but it does not tell you how much power your home uses while the sun is shining. These seven checks help you prepare for a useful assessment before choosing a system size or comparing prices.

This is a practical preparation checklist for landed homeowners. The programme references apply to TNB customers in Peninsular Malaysia; other supply areas have different arrangements. These checks support an assessment, not a system-size recommendation.

1. Start with electricity units, not just ringgit

Collect recent bills and, where possible, a full year. Note the billing dates and consumption in kilowatt-hours (kWh), alongside the amount paid. A change in cost can reflect usage, billing-period length or tariff adjustments.

Record whether the home already has solar. After installation, grid imports alone do not represent all household consumption because some electricity may come directly from the panels.

2. Record when the house is occupied

Make a simple diary for a representative working week and weekend. Note who is home in the morning, afternoon and evening, and when the main appliances run. Include work-from-home days, school holidays and regular periods away.

Start with a week to identify questions, then use longer records where available. A short diary cannot capture every seasonal change. Mark unusual days rather than treating them as typical.

3. Separate daytime loads from evening habits

List air-conditioners, water heating, cooking, laundry and any vehicle charging. Record approximate start and finish times. The purpose is to see which uses coincide with daylight, not to produce a precise appliance audit.

Illustrative example: an appliance drawing a constant 1 kW for two hours uses 2 kWh. Real appliances often cycle or vary their power, so their nameplate rating multiplied by operating hours is only an estimate. A qualified assessor can explain which measurements would improve it.

Solar output also varies with weather, shading, orientation and the installed equipment. A sunny afternoon should not be treated as the output available every day. The US Department of Energy’s homeowner guide explains these general performance factors; Malaysian programme rules come from local authorities.

4. Identify genuinely flexible routines

Some existing tasks can move into daylight, such as a laundry cycle when someone is home. Others cannot: evening meals, necessary cooling and medical equipment follow household needs.

Moving an existing task can increase direct solar use if surplus generation is available at that time. Creating extra consumption simply to use solar is different; it does not demonstrate an improvement in efficiency. Keep appliance instructions and normal supervision requirements in mind.

5. Keep direct use and export separate

Direct use means solar electricity supplies a load in the home as it is generated. Export is electricity sent to the grid. The two should be shown separately in a proposed assessment.

Under the Solar ATAP guideline, domestic exports are valued using the applicable Energy Charge, and unused offset is not carried into later billing periods. Do not assume exported units erase every charge on the bill.

6. Mark future changes as scenarios

A planned electric vehicle, additional air-conditioner or change in working hours may affect future demand. Record when the change is expected and when the equipment would operate.

Ask for the present household and the future scenario to be considered separately. A possible purchase next year is not measured consumption today. Likewise, occasional visitors should not automatically determine the size of a permanent installation.

7. Turn the record into an assessment brief

Bring the following information to the discussion:

• Electricity bills with consumption and billing dates.
• A working-day and weekend occupancy diary.
• Major appliance operating times and any available usage data.
• Confirmed future loads, listed separately from possibilities.
• Known shading, roof work or supply changes.

Ask the assessor to explain what is measured, what is estimated and which missing information could change the recommendation. Roof condition, electrical suitability and approvals still need their own checks.

What happens when you send your bill

You do not need a perfect diary to begin. Evolts’ published enquiry process has three steps:

1. Send a recent TNB bill and a roof photo through the enquiry form or WhatsApp. Add your usage notes if you have them.
2. An engineer reviews them and replies within one working day with an indicative system size, cost band and payback estimate.
3. If it looks worth pursuing, a site survey follows, usually within five working days. You only commit when you accept a firm quotation.

These initial figures are estimates, not a final design or guaranteed return. Before accepting a quotation, ask what roof or electrical work is included, what could cost extra, and how approvals affect the schedule. Your usage record helps frame those questions; it does not establish whether the roof can support an array.

Questions homeowners ask before enquiring

Still evaluating? Read the monitoring checks to discuss before installation and use afterwards. If you also manage business premises, continue with how factory closures change solar-use planning.