If you’re thinking of putting solar on a 4-bed with a south-facing roof, here’s what you can expect. You’ve got the best possible orientation in the UK: 978 kWh per kWp per year at 28° tilt, per PVGIS. But “best orientation” is not the same as “easy decision”. The actual challenge is what to do with the midday peak. That’s where the battery earns its keep.
I’ve got solar at home and I have been running panels on three orientations for three years: an SE and NW pitched roof, a nearly-flat gazebo, and a SW wall. What the south-facing arrays taught me is that yield is the easy part. The number that actually matters is how much of that yield you consume inside the house. Every kWh used directly saves 27.69p. Every kWh exported earns 5p on statutory SEG or 12p on Octopus Outgoing Fixed. The gap between those two numbers is where a 4-bed south-facing system either becomes a brilliant investment or a mediocre one.
A 4-bed family is typically out during the midday peak. Without a battery, a big south-facing array dumps most of that peak to the grid and you buy the evening back at 28p. With a battery, the same panels pay back in under 4 years. That is the whole argument for sizing this system right rather than big.
What This Roof Must Optimise For
- Battery storage from day one. South-facing panels concentrate output in a 4-5 hour midday window. Without a battery, a 4-bed household that is empty during the day will export 60%+ of generation at 5p/kWh instead of offsetting 27.69p grid imports in the evening. A battery is not optional here.
- Hybrid inverter sized for self-consumption, not maximum generation. A 3.6kW inverter with heavy overpanelling delivers nearly the same annual kWh as a 5kW unit because UK irradiance rarely pushes south-facing panels to full rated output. The budget system clips a few summer hours and loses almost nothing.
- Right-size the array to your consumption. With south producing the highest yield per panel of any orientation, adding more panels gives diminishing returns quickly. A 4-bed low-mid consumption home does not need 16 panels. 12 panels at 148% overpanel already generates more than the household consumes annually.
- Battery first, bigger array second. If cashflow forces a choice, take the battery. A 5kW south-facing array without storage exports 60%+ of its output at 5-12p and buys it back at 28p. A 3.6kW array with a 5kWh battery beats the 5kW array without one on ROI, every time, at typical UK consumption. I would not fit solar on a south roof without a battery. The only exception is a household with a heat pump running through the midday peak, which effectively IS the battery.
Opportunities
South-facing at 28° tilt produces 978 kWh per kWp per year in central England (PVGIS-SARAH3), the highest of any single-face orientation. That is 18% more than east-facing (805 kWh/kWp) and 22% more than west-facing (788 kWh/kWp). For the same number of panels, south produces the most energy.
The generation peak aligns with daytime loads: the dishwasher after breakfast, the washing machine mid-morning, and the fridge/freezer running continuously. If anyone works from home, the match improves further with computer, monitors, and heating/cooling running through the solar peak. A 4-bed household typically has higher base loads than smaller homes, which helps self-consumption even without a battery.
Your 4-Bed Consumption Profile
Low to Mid Consumption: 3,500 kWh/year
A 4-bedroom household on gas central heating with standard appliances uses around 3,500 kWh of electricity per year, based on Ofgem Typical Domestic Consumption Values. That is roughly £969 at the current price cap rate of 27.69p/kWh. Your base loads are lighting, fridge/freezer, cooking, washing, and entertainment. Most demand concentrates in the morning (7-9am) and evening (5-9pm), with a dip during the day unless someone works from home.
For a south-facing roof at this consumption level, the main concern is export waste. The panels generate heavily between 10am and 2pm while the house draws maybe 300-500W. A 5kW array without a battery would export over half its output. The budget system below pairs a modest battery with the panels to capture that midday surplus and release it during the evening cooking and entertainment window.
High Consumption: 7,500+ kWh/year
If you run a heat pump, charge an EV at home, or both, your annual consumption jumps to 7,500 kWh or more. A heat pump adds 3,000-5,000 kWh/year depending on your home’s insulation. An EV adds 2,000-3,500 kWh depending on mileage. Your annual bill could hit £2077+.
At this consumption level, your daytime base load is substantial. The heat pump cycles throughout the day, the hot water tank heats, and these loads overlap with whatever generation your south-facing panels produce. This is actually good news for solar because you will self-consume a much higher proportion of what you generate.
High consumption changes the economics of south-facing completely. The sharp midday peak that low-consumption homes waste gets absorbed by heat pump cycling and EV pre-conditioning. With a battery, the premium system below reaches 82% self-consumption, turning that midday spike into real grid savings rather than 5p export credits.
Budget Option
Solar Energy Concepts System Rating
System Specification
Inverter: Solis 3.6kW 5G Hybrid EH1 (£575-653)
- AC output: 3.6kW (G98 compliant, notification only)
- 2 independent MPPTs, 1 string each
- Max DC input: 600V / 15A per MPPT / 5.7kW total
- MPPT range: 90-520V
- Hybrid design allows battery addition later without replacing the inverter
Overpanelling target: 148% of the 3.6kW AC rating = 5,340W DC. South-facing panels will clip for a few hours on the brightest summer days when the array pushes past 3.6kW AC output. In UK conditions this costs you about 4% of theoretical yield, which the extra panel capacity more than compensates for. You gain far more in the shoulder months (March, April, September, October) when the additional panels boost output on shorter, cloudier days.
The DMEGC 450W is the cheapest panel in the UK at £61/panel, but its short-circuit current (Isc) of 15.4A exceeds the Solis EH1’s 15A per-MPPT limit. That rules it out for this inverter.
Panel Options
| Strategy | Panels | Total DC | Overpanel % | String Check |
|---|---|---|---|---|
| Best value | JA Solar 445W × 12 (6 + 6 per MPPT) | 5,340W | 148% | Voc: 6 × 39.1V = 234.6V < 600V. Vmp: 6 × 32.65V = 195.9V in 90-520V. Isc 14.43A < 15A. OK. |
| Smallest footprint | Aiko Neostar 490W × 10 (5 + 5 per MPPT) | 4,900W | 136% | Voc: 5 × 40.98V = 204.9V < 600V. Vmp: 5 × 34.4V = 172V in 90-520V. Isc 14.93A < 15A. OK. |
| Max overpanel | LONGi Hi-MO X6 455W × 12 (6 + 6 per MPPT) | 5,460W | 152% | Voc: 6 × 39.15V = 234.9V < 600V. Vmp: 6 × 32.98V = 197.9V in 90-520V. Isc 14.79A < 15A. OK. |
All panels are on the same south-facing roof, split evenly across both MPPTs. Because both strings face the same direction, they produce identical output and there is no mismatch loss. The JA Solar 445W at £64/panel is the cheapest compatible panel per watt (14.4p/W). The Aiko Neostar 490W has the highest efficiency at 24.5%, fitting 4,900W into just 10 panels if roof space is tight (pricing not confirmed from UK distributors at time of writing). The LONGi Hi-MO X6 455W at £73/panel gives 120W more total DC than the JA Solar option at the same panel count.
Battery
Fogstar 16.1kWh ECO (£1,850)
A 4-bedroom household averages 9.6 kWh per day. A small 5kWh battery barely covers half an evening for a family of four, so even on the budget tier, 16kWh is the sensible minimum. The Fogstar 16.1kWh at £1,850 is the best value per kWh in this range (£115/kWh usable). On a south-facing roof, the midday spike dumps a lot of energy in a short window. A larger battery absorbs more of that spike and releases it across the evening and overnight, which is where most of your consumption sits.
Total System Cost
- DIY: £3,400-3,700
- Installed: £7,600-8,200
DIY Feasibility
A south-facing single-roof system is the simplest possible solar install. All panels go on one face, connected as two identical strings of six. Cable runs are straightforward because both strings originate from the same roof plane. The Solis EH1 has clearly labelled MPPT1 and MPPT2 DC inputs plus a separate battery port. No complex wiring decisions.
You can mount the panels, run the DC cabling, and install the inverter yourself. You will need a qualified electrician to make the final AC connection to your consumer unit (Part P of building regulations). Budget £150-300 for this. No MCS certification is needed for the install itself, though you will not be eligible for SEG export payments without MCS. For a system sized for self-consumption, losing SEG income is negligible.
Expected Performance
| Metric | Low-Mid (3,500 kWh) | High (7,500 kWh) |
|---|---|---|
| Annual yield | 5,014 kWh | |
| Self-consumption (with 16.1 kWh battery) | 59% (2,954 kWh) | 95% (4,779 kWh) |
| Export | 41% (2,060 kWh) | 5% (235 kWh) |
| Grid savings | £818/year | £1323/year |
| Export income (SEG 5p) | £103/year | £12/year |
| Total annual saving | £921/year | £1335/year |
Premium Option
Solar Energy Concepts System Rating
System Specification
Inverter: Solis 5.0kW S5 Smart Hybrid (£707-770)
- AC output: 5.0kW (requires G99 application, not just notification)
- 2 independent MPPTs, 1 string each
- Max DC input: 600V / 15A per MPPT / 8.0kW total
- MPPT range: 90-520V
- Hybrid design with native battery port
Overpanelling target: 142% of the 5.0kW AC rating = 7,120W DC. The Solis S5 has 8.0kW max DC input, so 7.12kW sits comfortably within limits. With 16 panels split 8+8 across both MPPTs, each string handles its own voltage and current independently.
Panel Options
| Strategy | Panels | Total DC | Overpanel % | String Check |
|---|---|---|---|---|
| Best value | JA Solar 445W × 16 (8 + 8 per MPPT) | 7,120W | 142% | Voc: 8 × 39.1V = 312.8V < 600V. Vmp: 8 × 32.65V = 261.2V in 90-520V. Isc 14.43A < 15A. OK. |
| Smallest footprint | Aiko Neostar 490W × 14 (7 + 7 per MPPT) | 6,860W | 137% | Voc: 7 × 40.98V = 286.9V < 600V. Vmp: 7 × 34.4V = 240.8V in 90-520V. Isc 14.93A < 15A. OK. |
| Max overpanel | LONGi Hi-MO X6 455W × 16 (8 + 8 per MPPT) | 7,280W | 146% | Voc: 8 × 39.15V = 313.2V < 600V. Vmp: 8 × 32.98V = 263.8V in 90-520V. Isc 14.79A < 15A. OK. |
Battery
Fogstar 16.1kWh ECO (£1,850)
The premium battery target for a 4-bed home is 14.4 kWh or more (150% of the 9.6 kWh daily average). The Fogstar 16.1kWh exceeds this target and provides real multi-day resilience. On a south-facing roof, the battery absorbs the concentrated midday surplus that would otherwise go to export. In summer, the 16kWh stores enough to cover the entire evening and overnight period. In winter, it enables tariff arbitrage: charge overnight on Octopus Go at 7.5p/kWh, discharge during the day at 27.69p.
That 20p/kWh spread across 16kWh is £3.20 per day, or roughly £96/month in the darkest months when solar output drops below 2 kWh/day.
Total System Cost
- DIY: £3,900-4,300
- MCS installed: £9,300-10,200
G99 and MCS
At 5.0kW AC output, this system exceeds the G98 threshold of 3.68kW. You must apply for G99 permission from your DNO before connecting. This is a formal application, not a notification. Most DNOs approve residential G99 within 45 days, but some regions (notably SSEN in Scotland and parts of Southern England) can take longer if the local grid is constrained.
MCS certification is recommended for the premium option because: (a) you qualify for SEG export payments, which become meaningful at this generation level, (b) the battery enables time-of-use tariff strategies that require a certified installation for some suppliers, and (c) it protects your home insurance and property value.
When This Makes Sense vs Overkill
Worth it if: You have a heat pump, EV, or both, or plan to add one within 2-3 years. At high consumption, the premium system self-consumes 82% of its output. The 16.1kWh battery handles the south-facing midday peak and the evening demand gap completely. The bigger array also produces more usable kWh in winter when every bit counts.
Overkill if: You are a low-consumption 4-bed household with no plans to electrify heating or transport. At 3,500 kWh/year, the premium system still exports 53% of its output at 5-12p. The budget system (3.6kW + 5kWh battery, £3,550 DIY) saves £921/year. The premium system (5kW + 16kWh battery, £4,100 DIY) saves £1,053/year. £132/year more for £550 more upfront is a fine incremental trade on DIY. On MCS-installed it is a different story: £1,850 more upfront for the same £132/year extra is a 14-year payback on the incremental spend, which is not a trade worth making. Go budget if you are MCS-installing and low-consumption.
Expected Performance
| Metric | Low-Mid (3,500 kWh) | High (7,500 kWh) |
|---|---|---|
| Annual yield | 6,685 kWh | |
| Self-consumption (with 16.1 kWh battery) | 47% (3,166 kWh) | 82% (5,451 kWh) |
| Export | 53% (3,519 kWh) | 18% (1,234 kWh) |
| Grid savings | £877/year | £1509/year |
| Export income (SEG 5p) | £176/year | £62/year |
| Total annual saving | £1053/year | £1571/year |
Tariff Strategy and DNO Notes
Budget option: A flat-rate tariff works fine for the budget tier. Your primary savings come from self-consumption at 27.69p/kWh. The 16.1kWh battery captures the midday south-facing spike and shifts it to the evening. If you want to optimise further, Octopus Flux pays a higher export rate during the 4pm-7pm window, which aligns well with a south-facing system that still has late afternoon output.
Premium option: Octopus Go is the natural fit. Charge your battery overnight at 7.5p/kWh and discharge during the evening peak at 27.69p. In summer, solar handles the charging. In winter, cheap off-peak grid power fills the battery instead. The south-facing generation profile works well with Go because the system generates heavily during the day (when Go rates are standard) and the battery handles the rest.
DNO Region Considerations
South-facing systems export more aggressively at midday than E/W setups because all generation is concentrated in a 4-5 hour window. With the budget battery absorbing 5kWh of this peak, the grid impact is manageable, but it is worth noting for G99 applications.
G98 (budget, 3.6kW): Notification-only. All DNOs process this within days. No practical regional variation.
G99 (premium, 5.0kW): Application required. Turnaround varies by DNO:
Timeframes below are based on ENA Engineering Recommendation G99, which sets a statutory 45 working-day limit for residential G99 decisions, and each DNO’s published connections SLA. Actual turnaround varies by local grid capacity, application completeness, and seasonality.
- UKPN (London, South East, East): Generally fast, 20-30 working days
- WPD / National Grid ED (Midlands, South West, Wales): Moderate, 30-45 days
- NPG (North East, Yorkshire): Generally fast, 20-30 days
- SSEN (Scotland, parts of South): Can be slow, 45-60+ days. Known for grid constraint issues in rural areas
- ENW (North West): Moderate, 30-45 days
If you are in an SSEN area and planning a 5kW system, submit your G99 application early. Do not wait until the panels arrive.
ROI Comparison
| Budget DIY | Budget Installed | Premium DIY | Premium MCS | |
|---|---|---|---|---|
| Low-Mid Consumption (3,500 kWh/year) | ||||
| Upfront cost | £3,550 | £7,900 | £4,100 | £9,750 |
| Annual saving | £921 | £921 | £1053 | £1053 |
| Payback | 3.9 years | 8.6 years | 3.9 years | 9.3 years |
| 25-year return | £23,025 | £23,025 | £26,325 | £26,325 |
| High Consumption (7,500 kWh/year) | ||||
| Upfront cost | £3,550 | £7,900 | £4,100 | £9,750 |
| Annual saving | £1335 | £1335 | £1571 | £1571 |
| Payback | 2.7 years | 5.9 years | 2.6 years | 6.2 years |
| 25-year return | £33,375 | £33,375 | £39,275 | £39,275 |
Assumes flat electricity rate of 27.69p/kWh, SEG at 5p/kWh, no energy inflation, and 0.5% annual panel degradation. Real returns are likely higher as energy prices tend to rise over 25 years.
Generation Yield Source
All yield estimates in this guide are derived from PVGIS (Photovoltaic Geographical Information System), the European Commission’s free solar radiation database. PVGIS uses satellite-measured irradiance data and is the standard reference for solar yield calculations across Europe.
Simulation Parameters
| Parameter | Value |
|---|---|
| Location | 52.308°N, -0.717°W (Central England reference) |
| Roof slope | 28° |
| System loss | 14% |
| Database | PVGIS-SARAH3 |
Yield by Roof Face
| System | Face | PVGIS Aspect | E_y (kWh/kWp/yr) | DC Capacity | Annual Yield (pre-clip) |
|---|---|---|---|---|---|
| Budget | South | 0° | 978.0 kWh/kWp | 5.34 kWp | 5,223 kWh |
| Premium | South | 0° | 978.0 kWh/kWp | 7.12 kWp | 6,963 kWh |
Clipping factor applied: 0.96 (accounts for inverter limiting when DC input exceeds AC capacity).
Budget total annual yield after clipping: 5,014 kWh
Premium total annual yield after clipping: 6,685 kWh
You can verify these figures yourself using the PVGIS interactive tool. Enter your postcode for location-specific results:
Key Takeaways
- South-facing is the UK’s highest-yield orientation per kWp (978 kWh/kWp/year at 28° tilt, per PVGIS). Bigger is not automatically better.
- Battery is the single biggest ROI lever. Without it a 4-bed family exports 60%+ of the midday peak at 5-12p and buys it back at 28p.
- Budget 3.6kW + 12 panels + 5kWh battery (£3,550 DIY) pays back in 3.9 years at typical 4-bed consumption.
- Premium 5kW + 16 panels + 16kWh battery (£4,100 DIY) only earns out above ~5,000 kWh/year or with a heat pump/EV.
- MCS-installed systems pay back roughly 2x slower than DIY. If you’re MCS-installing and low-consumption, go budget.
Related Guides
- How roof tilt actually affects 10-year ROI. Three years of metered data on SE, NW, flat, and wall mounts.
- Start here: your guide to home solar. Read this first if you’re still deciding whether solar is right for you.
- Battery overview. Sizing, chemistry, and why storage is the ROI lever on most UK roofs.
- Seven solar myths. Including the “south-facing means you don’t need a battery” myth that specifically bites on this roof.
- Are solar panels worth it in 2026?. Full ROI breakdown.
- 2-bed south-facing roof. Same orientation, smaller household, leaner build.
- 4-bed NW/SE split roof. Same house size, two-string scenario, dual-MPPT build.
