Reducing imported energy is different from eliminating the bill. A grid-connected home can still pay contracted-power charges, taxes and for electricity used when solar output is low. Annual generation exceeding annual consumption does not mean the home is self-sufficient every hour.
Start with demand, not a bundle of equipment
Collect twelve months of electricity and heating bills, meter readings and occupancy patterns. Separate pool heating, air conditioning, hot water and vehicle charging. Fix unnecessary consumption and controls before sizing new equipment.
A holiday villa used mainly in summer has a different demand profile from a permanently occupied home with winter heating. Compare improvements under your own schedule, not a neighbour's best month.
What each technology can and cannot do
| Technology | Opportunity | Constraint |
|---|---|---|
| Solar PV | Replace some daytime grid imports | Weather, shade, usable roof and seasonal generation |
| Battery | Shift some surplus generation into the evening | Usable capacity, conversion losses, replacement cost and tariff spread |
| Heat pump | Provide heating or hot water using electricity | Heat loss, emitter temperatures and seasonal efficiency |
| Smart controls | Move suitable loads into solar hours | Occupancy, comfort and equipment compatibility |
Solar and heat pumps must be compared seasonally
A heat pump moves heat rather than producing it solely by electrical resistance. Its performance varies with outdoor temperature, hot-water or heating flow temperature, defrosting and installation design. A favourable laboratory figure is not a whole-year savings guarantee.
Solar can supply some of the electricity when generation and demand coincide. Heating demand may peak during periods with less solar output. A battery shifts energy in time; it does not create the winter generation shortfall. Pool heating and hot-water schedules should be considered separately.
Compare full costs and conservative assumptions
- Include equipment, installation, electrical or plumbing upgrades, access, tax and paperwork.
- Use the actual import tariff, export agreement and unavoidable charges.
- Model maintenance, financing and replacement separately from simple payback.
- Exclude unapproved grants and tax relief from the base case.
- Test lower solar output and lower import prices; both can reduce financial savings.
This guide does not claim a verified customer saving, property valuation increase or guaranteed payback. For transparent example arithmetic, see the illustrative villa planning exercise.
Choose the next specialist by the decision you need
Ben Hayden is this article's primary commercial owner for assessment and project oversight, linked in the research summary. Confirm the scope and terms of that advice. No review by Ben of the calculations on this page is claimed.
For delivery, the group separates planned electrical work, solar and storage (LIT) from heating, HVAC and pool heating (Agua-Therm). A whole-home plan should make those responsibilities explicit rather than presenting one generic installer as the owner of every service.