How to integrate solar, heat pump, and EV — a complete guide to a renewable home
By Fotovol·Updated 1 May 2026
1. Think in systems, not in components
Most people buy solar to lower their electric bill. Fine starting point — but if you'll have a heat pump or an EV in two years, today's panels won't keep up. Sizing isn't about your current consumption. It's about your consumption five years out.
A modern renewable home is an integrated system: solar produces, battery stores, the heat pump consumes huge amounts in winter, the EV consumes at night. Without a unified plan, you buy piecemeal and replace the inverter twice. With a plan, you do it once, scaled correctly.
If you're starting from zero, see how to begin with solar. This article is the next step: how the pieces fit together.
2. Solar PV — sizing for the entire load, not just current consumption
Real numbers for a renewable home: heat pump pulls 5–10 MWh/year (depends on insulation and floor area), EV 3–5 MWh/year at 15,000 km/year, the rest of the house (fridge, electric cooking, lights, IT) 3–4 MWh/year. Total: 11–19 MWh/year.
For a well-sited Romanian home in the south (1,000–1,100 kWh/kWp/year output), that means 8–12 kWp of panels to fully cover annual consumption. Not 4–5 kWp as your current gas-heavy bill suggests — gas doesn't show up in the electric bill.
The inverter must be hybrid (PV + battery integrated) from the start, even if you don't buy the battery now. A "PV-only" inverter becomes 5,000 RON of waste when you add the battery in two years.
Use the capacity calculator for precise sizing. For grid-injection legality, see what is a prosumer.
3. Battery storage — from "nice-to-have" to "core"
Without a battery, daytime solar surplus doesn't help you in the evening. The heat pump kicks in at 4 AM (pre-heat), the EV charges at night, the sun is at noon. That time-decoupling makes the battery non-optional — it's what lets you actually live off your own production.
Typical capacity for a complete home: 15–30 kWh LiFePO4. Below 15 kWh, you wake up on the grid; above 30 kWh, you're paying for winter (when you can't fully recharge anyway).
LiFePO4 (LFP) is the current standard — 6,000+ cycle life (15+ years), chemical safety, no thermal runaway. Avoid NMC or no-name AliExpress modules.
RON range: 25,000–60,000 installed (15–30 kWh, tier-2 → tier-1 brands). Second largest line item after the heat pump.
4. Heat pump — the single largest load in the house
Air-to-air (mini-splits) vs air-to-water (hydronic, connected to existing radiators or floor heating). For a renewable home, the standard pick is air-to-water — one system handles both space heating and DHW (domestic hot water), and connects to existing radiators without rebuilding.
COP 3–4 in Romanian winters (every electric kWh gives 3–4 thermal kWh). Sizing 8–14 kW thermal for 150–200 m² well-insulated. Insist on inverter modulating, not on/off — 20–30% consumption difference.
Watch for the thermal buffer (100–300 L inertial tank) — without it, the pump cycles too often and wears out fast. Buffer cost is small relative to the pump itself.
RON range: 20,000–50,000 installed (equipment + labor + buffer + plumbing).
5. EV Wallbox — the second largest load
Single-phase 7.4 kW vs three-phase 11/22 kW — depends on the home's grid connection and the speed you want. Recommendation: three-phase 11 kW if the home is three-phase (5 hours full charge vs 12 hours single-phase).
Dynamic load balancing is critical — if you charge the EV while the heat pump runs, without throttling you'd trip the main breaker. Modern wallboxes (Wallbox Pulsar, Easee, Zaptec, KEBA) integrate with a smart meter or directly with the hybrid inverter and adjust power live.
Confirm the home connection supports three-phase charging before you buy the wallbox — going from single- to three-phase is a 3–6 month DSO process.
RON range: 3,000–8,000 (wallbox + cable + labor + extra connection if needed).
6. Smart home / HEMS — the orchestrator
Home Assistant (open-source, recommended for flexibility) vs proprietary systems (Loxone, Tibber, Sonnen). HA runs on a Raspberry Pi or mini-PC, controls anything Zigbee/Z-Wave/Wi-Fi, and integrates with the hybrid inverter via local API or Modbus.
The automations that matter:
- Load shifting on solar surplus — start the dishwasher when surplus exceeds 2 kW
- EV charging when surplus is available — wallbox takes commands from HEMS, charges only when producing
- Heat pump weather-anticipating preheat — warm the house before cold days if the battery is full
Hardware RON: 1,000–3,000 (HA host + Zigbee dongle + temperature/humidity sensors + relays). Time cost: weekends for initial config, but saves 5–15% of residual bills via good orchestration.
7. Electric cooking, hot water, and other resistive loads
Induction aligns naturally with the solar peak (lunch and early-evening cooking, when sun is still active) — an advantage over gas that doesn't show up directly on the solar bill but matters for autonomy.
DHW: keeping the old electric tank is inefficient (constant standby losses). Coupled with the heat pump (if you went air-to-water), DHW takes ~1/3 of straight-electric. Alternative: a heat pump water heater standalone — similar savings without changing the heating system.
Washer, dryer, fridge — loads that HEMS schedules during production. An A+++ 9 kg washer plus a heat pump dryer are natural members of an optimized home.
RON for induction: 1,500–5,000 (3–4 zones, European brand). Heat pump water heater: 5,000–9,000.
8. Backup grid-down — islanded mode
How the hybrid inverter + battery keep the critical-loads circuit (fridge, freezer, lights, router, phone chargers) running for 12–24 hours autonomously. Requires a separate critical-loads panel at install time — adding it later costs more and means rewiring.
For rare blackouts (<2 days/year in urban Romania), the battery alone is enough. For rural settings or multi-day autonomy, add a propane or diesel generator as long backup (rarely needed, but psychological calm).
ATS (Automatic Transfer Switch) — auto-detects grid loss and isolates the home in under a second. Mandatory if you want invisible transitions; without it you get a 5–10 second blackout when the grid drops.
RON range: 5,000–15,000 (separate panel + ATS + optional 8 kW generator).
9. How it all integrates — simplified schematic + install order
Simplified electrical flow:
Sun → PV panels → Hybrid inverter → AC bus (home loads)
↘ DC bus → LiFePO4 battery
↘ Critical loads (backup, via ATS)
Grid ↔ Bidirectional meter ↔ Hybrid inverter (prosumer regime)
Recommended install order:
- Solar + hybrid inverter + battery — all in one electrical intervention (saves labor and produces a coherent system)
- Heat pump — can wait 6–12 months if budget is tight; you'll use it first the next winter
- EV wallbox — when the car arrives; needs a dedicated branch and DSO check
- HEMS / Home Assistant — last, once the rest is operational and you have data on how the house behaves
Watch out for three-phase — that's the decision that won't easily change later. If you plan a three-phase EV + a large heat pump + an 11+ kW wallbox, ask for three-phase from day one.
10. Reference build — typical RO 2026 home + a day in the life
Persona: 150 m², four occupants, southern Romania, one EV, currently gas heating, three-phase grid connection.
| Subsystem | Specs | RON |
|---|---|---|
| Solar PV | 10 kWp + hybrid inverter | 30,000 |
| Battery | 20 kWh LiFePO4 | 35,000 |
| Heat pump | 12 kW air-to-water + existing radiators + buffer | 35,000 |
| EV wallbox | 11 kW three-phase + connection upgrade | 5,000 |
| Cooking + DHW | Induction 4-zone + reusing existing thermal tank | 3,000 |
| HEMS | Home Assistant + sensors + relays | 2,000 |
| Gross total | 110,000 | |
| With Casa Verde | (up to 20,000 RON for solar) | ~90,000 |
Estimated payback: 8–12 years at 2026 energy prices, assuming fully-electric consumption (no gas) and average export surplus. Best case for new builds (zero compromise on insulation) rather than retrofits.
A day in the life:
- 11:00 — solar produces 8 kW, washer and dryer start automatically from HEMS, EV tops up to 80%, the rest goes into the battery
- 18:00 — sun fades, you cook on induction, the heat pump warms the house; consumption pulls from the still-full battery
- 23:00 — battery at 60%, you're still on your own production; the grid hasn't been touched today
- Winter — battery drops to 20% by morning, the heat pump pulls 1–2 kWh from the grid for 2 hours (minor cost, ideally on a night tariff)
For a quote on your specific build, request a quote from verified installers. For precise sizing, see the calculator. If the full build is out of reach, plug-in balcony kits are a more accessible entry point.