RV power is three systems that must match: what you draw, what you store, and what you recharge. Most failures are a mismatch rather than a fault — a 200 Ah bank running a 1,500 W inverter through a 100 W panel will be flat by the second evening, and no amount of new equipment fixes the arithmetic.
Shore power service
| Service | Voltage | Capacity | Runs |
|---|---|---|---|
| 15/20 amp | 120 V | 1,800–2,400 W | Charger, lights, laptop |
| 30 amp | 120 V | 3,600 W | One AC, fridge, microwave |
| 50 amp | 240 V | 12,000 W | Two ACs, everything |
A 50 amp coach on 30 amp service works, but only if you manage loads: one air conditioner, and the water heater off while the microwave runs.
Battery types
| Type | Usable capacity | Cycles | Cost |
|---|---|---|---|
| Flooded lead acid | 50% | 300–500 | $120–200 |
| AGM | 50% | 400–700 | $200–350 |
| Gel | 50% | 500–800 | $250–400 |
| Lithium (LiFePO4) | 80–90% | 2,000–5,000 | $500–1,200 |
Lithium costs more up front and less per usable amp-hour over its life. It also charges faster and weighs half as much for the same capacity.
Inverter sizing
| Load | Watts | Inverter |
|---|---|---|
| Lights, phone, laptop | 100–300 | 300–500 W |
| TV and fan | 300–600 | 600–1,000 W |
| Coffee maker | 900–1,500 | 1,500–2,000 W |
| Microwave | 900–1,500 | 2,000 W |
| Induction hob | 1,800 | 2,000 W+ |
Inverters are rated for continuous and peak. A 2,000 W inverter runs a 1,500 W load continuously and starts a 3,000 W surge for a second — enough for a compressor.
Solar input
| Panel | Real output per day |
|---|---|
| 100 W | 30–40 Ah |
| 200 W | 60–80 Ah |
| 400 W | 120–160 Ah |
| 600 W | 180–240 Ah |
Real output is 4–5 hours of good sun, not the panel rating. Shade, angle, and heat reduce it further; a flat-mounted panel on a hot roof produces about 60% of its rating.
Runtime by load
| Load | Draw | 100 Ah lithium |
|---|---|---|
| Lights and phone | 2–5 A | 20–40 h |
| Compressor fridge | 3–5 A average | 20–30 h |
| Laptop charging | 5–8 A | 12–20 h |
| Fan | 3–6 A | 15–30 h |
| Inverter + microwave | 90 A | ~1 h |
Amp-hours are the language that matters. Convert watts to amps at 12 V by dividing by 12: a 600 W load draws 50 A.
Three charging paths
| Path | Output | When |
|---|---|---|
| Shore power / charger | 30–80 A | At a hookup |
| Solar | 5–15 A per 100 W | Daylight |
| Alternator (DC-DC) | 30–50 A | While driving |
The alternator is the most underused path. A DC-DC charger turns a two-hour drive into a full battery, which changes how you plan travel days.
The planning arithmetic
- Add your daily amp-hours: fridge 40, lights 5, laptop 20, fan 15 — about 80 Ah.
- Multiply by days between charges.
- Divide by usable capacity: lithium 0.8, lead 0.5.
- Compare with your recharge: solar plus driving.
A 200 Ah lithium bank gives 160 Ah usable — two days at 80 Ah. A 200 W panel returns 60–80 Ah a day in good sun, so the system balances if you drive or see sun every other day.
One number to watch
A battery monitor is the single most useful upgrade in an RV electrical system. Without one you are guessing state of charge from a voltage reading that sags under load and recovers when the load stops.
With one, you learn that the fridge takes 40 Ah overnight and that the panel returns 60 by noon. That knowledge turns power planning from anxiety into arithmetic.
Common mistakes
| Mistake | Result |
|---|---|
| Sizing the inverter before the battery | Battery flat in an hour |
| Counting panel watts as output | Half the expected charge |
| Discharging lead acid below 50% | Shortened life |
| No battery monitor | Guessing state of charge |
| Mixing battery types | Uneven charging |
Where to go next
For portable options, see the power station guide; for hookups, the RV hookup guide; for van systems, the Class B guide.
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