Adjusted PDP8: why homeowners should design rooftop solar from the electricity bill

Decision 768/QD-TTg approving the adjusted Power Development Plan VIII sends a clear signal to the residential market: self-produced, self-consumed rooftop solar is no longer only a “green add-on”. It is becoming part of how Viet Nam balances fast electricity demand growth, energy security and household electricity costs.

What matters for homeowners

According to the Government portal, the adjusted plan targets that by 2030, 50% of residential homes use self-produced and self-consumed rooftop solar for on-site consumption, without selling electricity to the national grid. It also states that Viet Nam’s rooftop solar potential is about 48,200 MW, within total solar potential of about 963,000 MW.

For households, the practical keyword is self-consumption. The best PV system is not necessarily the largest one; it is the system that generates power when the home is actually using electricity: daytime air-conditioning, refrigeration, water pumps, work-from-home loads, or other steady appliances. When more solar electricity is consumed directly inside the house, grid purchases at higher tariff blocks can fall and the monthly bill becomes easier to control.

Why the bill must come first

Residential rooftop solar should be designed from consumption data, not from roof area or panel count alone. The first checks are monthly kWh over the latest 12 months, the main usage hours during the day, and large loads such as air-conditioners, water heaters, pumps, electric cooking or EV charging. If daytime consumption is high, self-consumption PV can work directly. If the home uses most electricity at night, PV size should be more conservative or storage should be considered as a supporting option rather than the starting point.

• High daytime load: prioritise a high self-consumption ratio.
• High night-time load: avoid oversizing without storage or load shifting.
• Heavy roof shading: savings can fall sharply even if nominal capacity looks large.
• Seasonal bills: use multi-month data, not only one peak month.

Where BESS fits

The adjusted plan refers to storage development for the power system and to storage requirements for some centralised solar cases. For households, BESS should be treated as a PV-enhancing layer: using surplus solar in the evening, supporting critical loads, or improving resilience. But if bill reduction is the first objective, the starting point remains a PV capacity matched to daytime load and roof quality.

Design assumptions to verify

• Prioritise self-consumption, not revenue from electricity sales.
• Count savings only on solar electricity actually used inside the home.
• Check roof structure, orientation, shading and electrical safety before quotation.
• Do not apply one fixed saving percentage to every household.

The practical conclusion is that policy is becoming more favourable for residential rooftop solar, but each household’s result still depends on bill-based design. Homeowners should start by reading their electricity bill, identifying daytime load, then choosing PV capacity and considering storage only when there is a clear reason. SMARTGEN can support bill analysis and self-consumption simulation before investment decisions.